Glucose-6-phosphate dehydrogenase (G6PD) deficiency

Table of Contents

What is G6PD deficiency?

A variety of factors can trigger acute hemolysis in G6PD-deficient individuals for example ingestion of fava beans (also known as favism), mothballs or  anti-malarial drugs. G6PD deficiency is an inherited hemolytic anemia due to a red cell enzyme defect. For the RBC to be fully functional as an oxygen carrier, there are 3 important factors involved. They are the condition of the red blood cell membrane, the metabolic pathways involved in maintaining cell survival as well as the condition of the hemoglobin. There are 4 major metabolic pathways involved and they are interconnected. The key actions of these pathways include energy supply to the system, oxidant reduction of the cell, maintaining hemoglobin in a reduced state and regulation of oxygen release. These pathways use enzymes to convert specific molecules into their intended metabolites for the optimal functioning of the red blood cells. 

G6PD is involved in the hexose monophosphate pathway in red blood cell metabolism and functions to convert hydrogen peroxide to water in the erythrocyte. The inheritance is sex-linked, affecting males and carried by females.  This disorder is one of the most common anemia disorders worldwide .The degree of deficiency varies and is often mild in black Africans, more severe in Orientals and most severe in Mediterraneans. 

Why is G6PD important?

G6PD deficiency affects the red blood cell metabolism pathway particularly the hexose monophosphate shunt. G6PD is the catalyst in the rate-limiting first step of the pentose phosphate pathway, which uses glucose-6-phosphate to convert nicotinamide adenine dinucleotide phosphate (NADP) into its reduced form, NADPH. In red blood cells, NADPH is critical in preventing damage to cellular structures caused by oxygen-free radicals (e.g., hydrogen peroxide). It does this by serving as a substrate to the enzyme glutathione reductase. Reduced glutathione can be used to convert hydrogen peroxide to water and prevent damage to cellular structures, particularly the cell wall of RBCs since they have limited capacity for repair once mature. When the red cell is challenged by an oxidant stress, for example moth balls in G6PD deficiency, both lipids and red cell membrane proteins become oxidized as there is not enough reduced glutathione produced to convert the increased level of oxidants to water. Hemoglobin denatures and precipitates intracellular to become Heinz bodies. The presence of rigid inclusions causes the red cell to be trapped in the spleen and sometimes splenic macrophages surgically excise the portion of the red cell that contains a Heinz body. In these circumstances, the red cell may escape with a gap, appearing as bite cells. These rigid and fragmented cells may also lead to intravascular hemolysis.

Causes of acute hemolysis in G6PD deficiency

A variety of infections and drugs can trigger acute hemolysis in G6PD-deficient individuals. Ingestion of fava beans may trigger acute, severe, intravascular haemolysis as a condition known as favism. The glycosides vicine and convicine in fava beans are responsible for hemolysis. They generate aglycones that auto-oxidize and produce free radicals. Other agents that may cause hemolytic anemia in G6PD deficiency include mothballs, infections and other acute illnesses for example diabetic ketoacidosis and oxidative drugs for example antimalarials, analgesics and sulphonamides and sulphones. 

Features of G6PD deficiency

G6PD-deficiency is usually asymptomatic unless triggered by an oxidant. There could be neonatal jaundice too. The acute hemolytic anemia is caused by rapidly developing intravascular hemolysis with hemoglobinuria (blood in the urine). The anemia may be self-limiting as new young red cells are made with near normal enzyme levels. 

What are the different variants of G6PD deficiency, and how do they influence severity?

G6PD deficiency, an X-linked genetic disorder, exhibits a spectrum of severity due to various mutations in the G6PD gene. These mutations, known as variants, affect the enzyme’s activity, impacting red blood cell susceptibility to oxidative stress and influencing the severity of symptoms. 

ClassSeverityEnzyme ActivityClinical SymptomsPrevalence
IMost severe, leading to chronic non-spehrocytic hemolytic anemia (CNSHA)< 10%Constant fatigue, jaundice, splenomegaly and possible gallstonesRelatively rare 
IISevere, causing acute hemolytic anemia triggered by specific exposures 10 – 30%Episodes of fatigue, dark urine, abdominal pain and jaundice after triggersMore common than Class I
IIIModerate, with potential for mild acute hemolytic anemia after triggers30 – 60%May experience mild hemolytic episodes but often asymptomaticMore common than Classes I and II
IVMild, with very rare hemolysis even with triggers60 – 80%Usually asymptomaticRelatively common
VVery mild, with no hemolysis even after triggers> 80%Usually asymptomaticRelative Common

Additional Notes:

  • This classification is based on the World Health Organization (WHO) system, but other classification systems exist.
  • The severity of symptoms can vary within each class due to individual genetic backgrounds, environmental factors, and nutritional status.
  • Genetic testing can help identify the specific G6PD variant and potential severity.

How do I test for G6PD deficiency?

General laboratory tests

Between crises the blood count is normal. In a crisis, the FBC would have low hemoglobin level and reticulocytosis and the blood film may show contracted and fragmented cells with bite cells and blister cells which have had Heinz bodies removed by the spleen. 

Specific tests

Specific tests include decreased fluorescence in the fluorescence spot test and Heinz bodies may be seen in the reticulocyte preparation particularly if the spleen is absent. DNA analysis will be positive for the gene mutation. Biochemical parameters will show increased serum bilirubin and lactate dehydrogenase levels but reduced serum haptoglobin level. 

Normal G6PD activity: Bright green fluorescence. Intermediate G6PD activity: Reduced or yellowish fluorescence. No or very weak fluorescence.
This image depicts the results of a G6PD fluorescent spot test, a diagnostic tool for detecting glucose-6-phosphate dehydrogenase (G6PD) deficiency. The varying intensity of fluorescence indicates the level of G6PD activity in each sample. A bright green fluorescent spot signifies normal G6PD activity, while a reduced or yellowish fluorescence suggests intermediate G6PD activity. The absence or very faint fluorescence indicates deficient G6PD activity. This test is crucial for early diagnosis and management of G6PD deficiency.

How is G6PD deficiency treated?

Treatment and management include removing the underlying cause for example drugs must be stopped for treatment and blood transfusion where necessary for severe anemia. Underlying infections must also be treated and if indicated, splenectomy may be carried out.

Key Points of G6PD deficiency


An inherited hemolytic anemia due to red cell enzyme defect. X-linked recessive disorder – full expression only seen in males. 

Epidemiology of G6PD deficiency

Approximately 5% of the global population.

Image depicting a world map highlighting the geographic distribution of G6PD deficiency, with varying shades of color representing different levels of prevalence
Frequency of G6PD-deficient males in worldwide distribution. Most commonly affected countries are Western Africa, Middle East, the Mediterranean and Southeast Asia.

Signs and symptoms

  • Usually asymptomatic
  • Acute intravascular hemolytic anemia and hemoglobinuria during crises
  • Neonatal jaundice / hyperbilirubinemia

Crises causes of G6PD deficiency

  • Fava beans
  • Oxidative drugs (antimalarial drugs)
  • Antihelminths (mothballs)
  • Aspirin in high doses
  • Infections
  • Sulphonamides

Pathophysiology of G6PD deficiency

Image showcasing the mechanism of hemolysis in a G6PD crisis, highlighting the role of oxidative stress in damaging red blood cell membranes. The diagram describes a red blood cell in G6PD deficiency experiencing oxidative stress, triggering formation of Heinz bodies and removal by the spleen, creating bite cells and leading to hemolytic anemia. #G6PDdeficiency #HemolyticAnemia
This image depicts the cascade of events leading to hemolysis in G6PD deficiency, triggered by oxidative stress. Individuals with G6PD deficiency lack a key enzyme (glucose-6-phosphate dehydrogenase) crucial for the hexose monophosphate shunt (HMP shunt) – a pathway generating NADPH, an antioxidant. Exposure to stressors like fava beans, infections, or certain medications generates damaging free radicals. Without sufficient NADPH production, red blood cells lack the antioxidant power to combat these free radicals, leading to oxidative damage. Damaged hemoglobin within red blood cells aggregates, forming insoluble clumps called Heinz bodies (dark purple circle). The spleen, acting as a filter, recognizes and removes these damaged red blood cells, engulfing them and leaving behind “bite cell” fragments (red crescent). The loss of red blood cells leads to hemolytic anemia, characterized by fatigue, jaundice, and dark urine.

Laboratory investigations for G6PD deficiency

Confirmatory / Screening tests 

Full blood count and Peripheral blood characteristics in crises

Full blood count: ↓ hemoglobin, reticulocytosis. 

Peripheral blood smear: Moderate anisopoikilocytosis, polychromatic cells, microspherocytes and bite cells.

Other important investigations and expected results

  • ↑ serum bilirubin.
  • ↑ lactate dehydrogenase. 
  • ↓ serum haptoglobin.

Treatment and management of G6PD deficiency

  • Stop ingestion of oxidative drugs or fava beans
  • Transfuse packed red cells if necessary
  • Treat underlying infection if present
  • Splenectomy may ameliorate hemolytic anemia in rare chronic hereditary nonspherocytic hemolytic anemia

Frequently Asked Questions (FAQs)

What is the difference between G6PD deficiency and hemolytic anemia?

G6PD deficiency and hemolytic anemia are not the same, although they are closely related:

G6PD deficiency

  • Genetic disorder: This is a genetic condition where you have a reduced amount of the enzyme glucose-6-phosphate dehydrogenase (G6PD) in your red blood cells. The gene that produces G6PD can be found on the X-chromosome. 
  • Underlying cause: This enzyme helps protect red blood cells from damage caused by oxidative stress. Without enough G6PD, red blood cells are more susceptible to damage and breakdown.
  • Not always symptomatic: Many people with G6PD deficiency may never experience any symptoms, especially if they avoid triggers like certain medications, fava beans, or infections.

Hemolytic anemia

  • Symptom, not a disease: This is a condition where red blood cells are destroyed faster than they can be produced by the body. This can lead to various symptoms like fatigue, weakness, pale skin, jaundice, and dark urine.
  • Can have various causes: G6PD deficiency is one of many causes of hemolytic anemia, but other causes include autoimmune diseases, infections, sickle cell disease, and certain medications.
  • Always symptomatic: People with hemolytic anemia will always experience at least some symptoms, although the severity can vary depending on the cause and individual factors.

In simpler terms, G6PD deficiency is a genetic predisposition, while hemolytic anemia is a symptom that can be caused by various factors, including G6PD deficiency.

What happens if you have G6PD?

The impact of having G6PD deficiency depends on several factors, primarily the specific variant you have and its associated enzyme activity level. Here’s a breakdown of the potential outcomes:

Most people with G6PD deficiency never experience any symptoms. They may go their entire lives unaware they have the condition. This is because some variants have minimal impact on enzyme activity, making red blood cells relatively resilient to oxidative stress even without the full enzyme function.

However, for those with more severe variants:

  • Hemolytic anemia: This is the main concern and happens when red blood cells are destroyed faster than the body can replace them. Symptoms can include fatigue, weakness, pale skin, jaundice (yellowing of the skin and eyes), dark urine, and rapid heartbeat.
  • Triggers: Hemolytic episodes are often triggered by exposure to certain substances, like fava beans, some medications, infections, or even certain foods. Avoiding these triggers is crucial in managing the condition.
  • Severity variations: The severity of hemolytic episodes can vary significantly depending on the variant and individual factors. Some people may experience mild and infrequent episodes, while others may have severe and life-threatening attacks.

Additional considerations

  • Geographical variations: Certain variants are more common in specific regions, impacting the overall prevalence and public health considerations.
  • Prenatal screening: In some areas, testing for G6PD deficiency during pregnancy is offered to identify newborns who might require extra care and early intervention.
  • Management: Living with G6PD deficiency effectively involves understanding your specific variant, identifying and avoiding triggers, and seeking medical attention promptly if symptoms arise.

What are G6PD foods to avoid?

It’s important to clarify that while certain foods have historically been associated with triggering hemolytic episodes in individuals with G6PD deficiency, the term “G6PD foods to avoid” can be misleading and overly simplistic. The key factor in managing G6PD and preventing hemolysis is individual-specific trigger identification and avoidance, not a comprehensive list of banned foods.

Here’s what you need to know:

Triggers vary based on individual

  • The specific foods or substances that trigger hemolysis differ depending on the G6PD variant a person has and their individual sensitivity. Not everyone with G6PD needs to avoid the same foods.
  • Consulting a healthcare professional is crucial for personalized guidance on potential triggers based on your specific variant and medical history.
  • Relying solely on a generic list of “G6PD foods to avoid” can be counterproductive and miss important individual variations.

Commonly reported triggers

  • Fava beans: The most well-known trigger, responsible for the historical term “favism” associated with G6PD deficiency. However, not everyone with G6PD reacts to fava beans.
  • Certain medications: Some antibiotics, antimalarial drugs, and other medications can trigger hemolysis in individuals with G6PD. It’s crucial to inform your doctor about your G6PD status before taking any medication.
  • Stress and infections: These can also act as triggers in some individuals. Managing stress and seeking prompt medical attention during infections is important.
  • Other potential triggers: While less common, certain foods like bitter melon, moth beans, and even some spices have been reported as triggers in some cases.

What drugs should be avoided in G6PD?

As with food triggers, specific drugs to avoid in G6PD deficiency vary depending on the individual and their specific variant. While a generic list exists, it’s important to remember that it’s not a substitute for personalized medical advice. Here’s what you need to know:

Individuality Matters

  • The specific drugs that trigger hemolysis in G6PD deficiency depend on the enzyme activity level associated with the individual’s variant. What might be safe for one person could be a major trigger for another.
  • Relying solely on a list of “drugs to avoid in G6PD” can be dangerous and miss important individual variations.
  • Always consult your healthcare professional for a personalized list of medications to avoid based on your specific G6PD variant and medical history.

Commonly Reported Triggers

  • Antimalarial drugs: Medications like quinine, chloroquine, and primaquine are known triggers for many G6PD variants.
  • Sulfa drugs: Antibiotics like trimethoprim-sulfamethoxazole (Bactrim) and some sulfa-based diuretics can pose risks.
  • Nitrofurantoin: An antibiotic commonly used for urinary tract infections.
  • Dapsone: Used for leprosy and some skin conditions but can trigger hemolysis in G6PD individuals.

Additional Notes

  • Many other medications might have varying risk levels depending on the G6PD variant.
  • Even seemingly harmless drugs like aspirin in high doses can be problematic for some individuals.
  • It’s crucial to inform your doctor about your G6PD status before taking any medication, even over-the-counter drugs.
  • Your doctor can review your specific variant, medical history, and current medications to create a safe and effective treatment plan.

What happens to a baby with G6PD?

Babies born with G6PD deficiency can experience a range of outcomes, depending on the severity of their variant and other factors:

Most Cases

  • No symptoms: Many babies with G6PD deficiency, especially those with milder variants, have no noticeable symptoms and develop normally. Their G6PD levels may be lower than average, but their red blood cells still function adequately.
  • Jaundice: This is a common occurrence in newborn babies with G6PD deficiency, particularly in the first few days of life. It happens when bilirubin, a byproduct of red blood cell breakdown, builds up in the blood faster than the liver can process it. Jaundice usually resolves itself within a week or two with increased feeding and phototherapy (light therapy).
  • Mild anemia: Some babies may experience mild anemia, leading to symptoms like fatigue and pale skin. This usually improves with age and proper management.

Severe Cases

  • Severe anemia: In babies with severe variants of G6PD deficiency, red blood cell breakdown can be significant, leading to severe anemia and that it is more likely to be severe enough to cause kernicterus. This can require blood transfusions and close medical monitoring.
  • Complications: In rarer cases, severe hemolytic episodes can trigger other complications like liver problems, kidney problems, and heart failure.

Important Factors

  • Variant type: The severity of symptoms and potential complications depend heavily on the specific G6PD variant the baby has. Some variants are much more severe than others.
  • Trigger exposure: Avoiding triggers like certain medications, fava beans, and infections is crucial for preventing hemolytic episodes.
  • Early diagnosis and management: Early identification of G6PD deficiency allows for proactive measures to avoid triggers and address any problems promptly, improving the baby’s health outcomes.

What are the most common triggers for hemolytic crisis in G6PD-deficient individuals?

While there are several triggers for hemolytic crisis in G6PD-deficient individuals, the most common ones fall into three main categories:

1. Medications

  • Antimalarial drugs: Drugs like primaquine, chloroquine, and quinine are known triggers for many G6PD variants.
  • Sulfa drugs: Antibiotics like trimethoprim-sulfamethoxazole (Bactrim) and some sulfa-based diuretics can pose risks.
  • Nitrofurantoin: An antibiotic commonly used for urinary tract infections.
  • Dapsone: Used for leprosy and some skin conditions but can trigger hemolysis in G6PD individuals.
  • Other medications: Even seemingly harmless drugs like aspirin in high doses can be problematic for some individuals.

2. Infections

  • Viral infections: Infections like hepatitis A and B, typhoid fever, and pneumonia can trigger hemolysis in G6PD individuals.
  • Bacterial infections: Certain bacterial infections, particularly those requiring specific antibiotics listed above, can also be triggers.
  • Parasitic infections: Malaria infection itself doesn’t trigger hemolysis, but medications used to treat it often do.

3. Other triggers

  • Fava beans: The most well-known trigger, responsible for the term “favism” associated with G6PD deficiency. However, not everyone with G6PD reacts to fava beans.
  • Stress and emotional strain: Excessive physical or emotional stress can trigger hemolysis in some individuals.
  • Oxidative stress: Exposure to certain chemicals or environmental factors that generate free radicals can also trigger hemolysis.

How does G6PD deficiency affect other medical conditions or treatments?

G6PD deficiency can have various impacts on other medical conditions and treatments, mainly due to its influence on red blood cell health and susceptibility to oxidative stress. Here’s a breakdown of potential interactions:

Increased susceptibility to infections

  • Damaged red blood cells are less efficient at carrying oxygen and fighting off infections, potentially increasing susceptibility to bacterial and viral infections.
  • Certain antibiotics used to treat infections can trigger G6PD-related hemolysis, requiring careful medication selection and monitoring.

Complications during surgery

  • Pre-operative evaluation for G6PD deficiency is crucial to prevent hemolysis during surgery due to potential blood loss and oxidative stress.
  • Transfusion of G6PD-normal red blood cells might be necessary in specific cases to manage hemolytic complications during surgery.

Impact on certain medical conditions

  • Sickle cell anemia: Individuals with both G6PD deficiency and sickle cell anemia might experience more severe hemolysis due to the additive effect on red blood cell fragility.
  • Thalassemia: While less common, co-occurrence with G6PD deficiency might further complicate red blood cell health management.

Challenges with certain treatments

  • Chemotherapy: Certain chemotherapy drugs can trigger hemolysis in G6PD-deficient individuals, requiring dose adjustments or alternative medications.
  • Radiation therapy: Radiation therapy, particularly in areas rich in red blood cell production, can increase oxidative stress and potentially trigger hemolysis.

Overall, G6PD deficiency doesn’t necessarily preclude other medical conditions or treatments, but it requires careful consideration and management by healthcare professionals.

Can G6PD deficiency be misdiagnosed as other conditions? If so, how can we avoid this?

Yes, G6PD deficiency can sometimes be misdiagnosed as other conditions, especially in its milder forms. This can delay proper diagnosis and management, potentially leading to unnecessary treatment for the wrong condition. Here’s a deeper look at why misdiagnosis occurs and how it can be prevented:

Reasons for Misdiagnosis

  • Non-specific symptoms: Early signs like fatigue, pale skin, and jaundice can be common to various other conditions like anemia, iron deficiency, or infections. Without a high index of suspicion, G6PD deficiency might be overlooked.
  • Mild cases with infrequent or subtle symptoms: Individuals with milder variants might not experience frequent or obvious hemolytic episodes, making diagnosis less apparent.
  • Lack of awareness among healthcare professionals: G6PD deficiency is less common in some regions, and healthcare professionals might not readily consider it as a diagnostic possibility.
  • Limited or unreliable testing: Inaccessible or inaccurate diagnostic tests, especially in resource-limited settings, can contribute to misdiagnosis.

Preventing Misdiagnosis

  • Raising awareness: Educating healthcare professionals about G6PD deficiency, its signs and symptoms, and high-risk populations is crucial.
  • Comprehensive clinical history: Detailed medical history, including family history and potential triggers like fava beans or medications, can provide valuable clues.
  • Accurate and accessible testing: Utilizing reliable tests like the quantitative G6PD enzyme assay is essential for confirmation or ruling out G6PD deficiency.
  • Maintaining a high index of suspicion: In areas with high G6PD prevalence or for individuals with suggestive symptoms, a high degree of suspicion can promote timely diagnosis.

What are the differential diagnoses for G6PD?

Diagnosing G6PD deficiency isn’t always straightforward, especially in milder cases or when symptoms overlap with other conditions. Here’s a list of potential differential diagnoses, conditions that might initially seem like G6PD deficiency but require further investigation:

Non-spherocytic hemolytic anemias

  • Thalassemia: Genetic disorder affecting hemoglobin production, leading to anemia and similar symptoms like fatigue and pale skin.
  • Autoimmune hemolytic anemia: Immune system attacks red blood cells, causing destruction and symptoms similar to G6PD deficiency.
  • Enzymopathies: Deficiencies in other red blood cell enzymes like pyruvate kinase can also cause hemolysis and mimic G6PD symptoms.
  • Microangiopathic hemolytic anemia: Certain conditions like HELLP syndrome or thrombotic thrombocytopenic purpura can damage red blood cells in small blood vessels, leading to hemolysis.

Other conditions with some overlapping symptoms

  • Iron deficiency anemia: This can cause fatigue, pale skin, and weakness, mimicking G6PD deficiency but responds differently to treatment.
  • Vitamin B12 or folate deficiency: These deficiencies can also cause anemia and pale skin, requiring specific vitamin supplementation.
  • Chronic infection: Some chronic infections can lead to mild anemia and fatigue, potentially appearing similar to G6PD deficiency.
  • Liver disease: Liver problems can interfere with red blood cell production and cause jaundice, a symptom sometimes seen in G6PD deficiency.

Distinguishing factors

  • Detailed medical history: Exploring family history, potential triggers, and past episodes can differentiate G6PD deficiency from other conditions.
  • Physical examination: Checking for specific signs like splenomegaly (enlarged spleen), common in chronic hemolysis, can provide clues.
  • Laboratory tests: G6PD enzyme assay is the definitive test for diagnosis, but other blood tests like complete blood count, reticulocyte count, and bilirubin levels can help distinguish between different causes of anemia and jaundice.

Importance of accurate diagnosis

  • Differentiating G6PD deficiency from other conditions ensures appropriate treatment and management.
  • Unnecessary treatments for misdiagnosed conditions can be avoided.
  • Knowing the specific diagnosis allows for effective prevention strategies for G6PD patients, like avoiding triggers.

How is G6PD deficiency diagnosed, and what tests are typically used?

The diagnosis of G6PD deficiency involves a combination of factors, including:

1. Clinical history

  • Discussing your symptoms, family history, potential triggers (medications, fava beans, infections), and ethnicity, as G6PD deficiency is more common in certain populations.

2. Physical examination

  • Checking for signs like jaundice (yellowing of the skin and eyes), pale skin, and enlarged spleen, which can indicate hemolysis.

3. Laboratory tests

  • Quantitative G6PD enzyme assay: This is the definitive test for G6PD deficiency and measures the activity level of the G6PD enzyme in red blood cells.
  • Complete blood count (CBC): This checks for anemia, including red blood cell count, size, and shape, and helps differentiate types of anemia.
  • Reticulocyte count: This measures newly formed red blood cells, indicating the bone marrow’s response to hemolysis.
  • Bilirubin levels: This helps assess liver function and potential jaundice.
  • Other tests: In some cases, additional tests like fluorescent spot test (FST) or genetic testing may be used.

Choosing the right tests

  • The specific tests chosen depend on your individual situation and initial findings.
  • The G6PD enzyme assay is crucial for confirmation, but other tests provide supporting information.

Interpretation of results

  • G6PD enzyme activity levels below a certain threshold (typically 30% of normal) indicate deficiency.
  • However, severity varies based on the specific variant and individual factors.
  • Combining test results with clinical history and physical examination helps pinpoint the diagnosis.


  • Newborn screening for G6PD deficiency is recommended in some regions with high prevalence.
  • Early diagnosis is crucial for preventing complications and initiating proper management.
  • Consult a healthcare professional for interpreting your specific test results and understanding their implications.

What are the limitations of current G6PD testing methods?

While current G6PD testing methods have significantly improved diagnosis and management of the condition, they still have some limitations:

1. Accuracy

  • Qualitative tests: These tests, like the Fluorescent Spot Test (FST), provide a yes/no answer for deficiency but don’t measure enzyme activity levels. This can be misleading, especially for heterozygous females who might have borderline enzyme activity but still be at risk of hemolysis under certain triggers.
  • Quantitative tests: These tests, like the G6PD enzyme assay, measure enzyme activity but may not accurately reflect individual sensitivity to triggers or the full spectrum of G6PD variants.

2. Accessibility

  • Cost: The G6PD enzyme assay can be expensive, limiting access in resource-limited settings where the deficiency is most prevalent.
  • Equipment and expertise: Performing the G6PD enzyme assay requires specialized equipment and trained personnel, further limiting accessibility in certain regions.

3. Individual variability

  • Enzyme activity levels: Even within the same G6PD variant, individual enzyme activity can vary, making it challenging to predict individual risk of hemolysis based solely on enzyme levels.
  • Trigger sensitivity: Individual susceptibility to triggers can vary, and current tests might not fully capture this variability.

4. Newborn screening

  • False positives: Newborn screening programs using qualitative tests can have high false-positive rates, potentially leading to unnecessary anxiety and follow-up tests.
  • Limited variant detection: Newborn screening programs might not detect all G6D variants, potentially missing individuals at risk.

Ongoing research

  • New technologies like point-of-care tests and genetic analysis are being explored to improve accuracy, accessibility, and individual-specific risk assessment.
  • Efforts are underway to develop more affordable and user-friendly testing methods for resource-limited settings.


While current G6PD testing methods have limitations, they remain crucial for diagnosis and management. Ongoing research aims to address these limitations and ensure accurate, accessible, and personalized testing for all individuals potentially affected by G6PD deficiency.

What are the risks of a G6PD test?

The risks associated with a G6PD test are generally minimal. The most common test, the quantitative G6PD enzyme assay, involves drawing a small amount of blood, similar to any routine blood test. Potential risks associated with blood draws include minor discomfort, bruising, or fainting, but these are rare and usually mild.

For newborn screening, a heel prick is used, which might cause slight discomfort but is generally well-tolerated by babies. Some qualitative tests like the FST use chemicals that could cause skin irritation in rare cases.

Overall, the benefits of G6PD testing far outweigh the minimal risks. Early diagnosis and proper management can significantly improve health outcomes for individuals with G6PD deficiency. If you have any concerns, discuss them with your healthcare professional before the test.

How do you prepare for a G6PD test?

The good news is, there’s no special preparation needed for most G6PD tests! You typically don’t need to fast or avoid food and drinks beforehand. However, there are a few things to keep in mind:

  • Inform your doctor about any medications you’re taking, including prescriptions, over-the-counter drugs, and herbal supplements. Some medications can interfere with test results.
  • Mention if you’ve recently been exposed to potential triggers like fava beans or certain antibiotics, as this might affect the timing of your test.
  • Wear comfortable clothes with easy access to your arm for the blood draw.
  • Bring a list of questions you have for your doctor about the test and G6PD deficiency in general.

What happens after a G6PD test?

What happens after a G6PD test depends on the specific type of test and your individual results. Here’s a breakdown:

Quantitative G6PD Enzyme Assay

  • Normal results: If your enzyme activity levels are within the normal range, you likely don’t have G6PD deficiency. Your doctor will discuss your results and provide guidance based on your overall health and any risk factors.
  • Abnormal results: If your enzyme activity levels are below the normal range, this indicates G6PD deficiency. Your doctor will discuss the severity based on the level of deficiency and explain what it means for you. They will also recommend further tests if needed, such as genetic testing to identify the specific variant you have.

Qualitative Tests

  • Negative results: If the test doesn’t show G6PD deficiency, you likely don’t have it. However, remember that qualitative tests are less accurate than the quantitative assay. Your doctor might recommend the quantitative assay for confirmation or further monitoring.
  • Positive results: A positive result suggests you might have G6PD deficiency, but it needs confirmation with the quantitative assay. Your doctor will discuss the next steps, which likely involve the quantitative test.

Newborn Screening

  • Positive results: If newborn screening indicates G6PD deficiency, further testing with the quantitative assay is needed for confirmation. Once confirmed, your doctor will discuss the diagnosis, potential risks, and necessary management strategies with you and your baby’s pediatrician.

What are the current guidelines for medication and dietary management in G6PD patients?

Managing G6PD deficiency involves avoiding triggers that can trigger hemolytic episodes, primarily certain medications and foods. Here’s an overview of current guidelines:

Medication Management

  • Avoiding triggers: The key principle is to avoid medications known to trigger hemolysis in G6PD individuals. These include:
    • Antimalarial drugs: Primaquine, chloroquine, and quinine.
    • Sulfa drugs: Trimethoprim-sulfamethoxazole (Bactrim) and some sulfa-based diuretics.
    • Nitrofurantoin: An antibiotic commonly used for urinary tract infections.
    • Dapsone: Used for leprosy and some skin conditions.
    • Other potential triggers: Aspirin in high doses, certain anti-tuberculosis medications, and some antifungals.
  • Alternatives and dose adjustments: When necessary medications cannot be avoided, alternative medications or adjusted dosages might be considered under close medical supervision.
  • Clear communication: Always inform your doctor and pharmacist about your G6PD deficiency before taking any medication, including over-the-counter drugs and herbal supplements.

Dietary Management

  • Fava beans: The most well-known dietary trigger, responsible for “favism” in G6PD individuals. However, not everyone with G6PD reacts to fava beans.
  • Other potential triggers: In some cases, certain vegetables like broad beans, lentils, and even spices might be triggers, but this varies significantly depending on individual sensitivity.
  • General guidelines: Focus on a balanced diet rich in fruits, vegetables, and whole grains. Stay hydrated and avoid excessive intake of processed foods and sugary drinks.
  • Personalized approach: Individual sensitivity and potential triggers should be identified through consultation with a healthcare professional and dietitian to create a personalized dietary plan.

Additional Considerations

  • Stress and infections: These can also act as triggers for hemolysis in some individuals. Managing stress and seeking prompt medical attention during infections is crucial.
  • Regular checkups: Regular follow-up appointments with your doctor are essential for monitoring your G6PD status, adjusting management strategies if needed, and identifying any potential complications.
  • Education and awareness: Educating yourself and others about G6PD deficiency can empower you to manage your health effectively and advocate for yourself in medical settings.

What are the long-term complications associated with G6PD deficiency?

While G6PD deficiency can be effectively managed with proper precautions and treatment, there are potential long-term complications if left unaddressed or poorly managed. Here’s an overview of the key risks:

Increased risk of infections

  • Damaged red blood cells are less efficient at fighting off infections, making individuals with G6PD deficiency more susceptible to bacterial and viral infections. This can lead to frequent infections, delayed recovery, and potential complications like pneumonia.

Spleen enlargement (splenomegaly)

  • Frequent hemolytic episodes can cause the spleen, an organ that filters blood, to overwork and enlarge. This can further reduce red blood cell production and contribute to anemia.


  • Increased breakdown of red blood cells leads to higher levels of bilirubin, a byproduct that can form gallstones in the gallbladder. These can cause pain, inflammation, and potential complications if left untreated.

Kidney problems

  • Severe hemolytic episodes can overwhelm the kidneys with bilirubin, leading to kidney damage in rare cases.

Delayed growth and development

  • In children with severe G6PD deficiency, chronic anemia can hinder growth and development, affecting height, weight, and cognitive function.

Increased risk of death

  • In rare and extreme cases, severe hemolytic crises with complications like kidney failure or heart problems can be life-threatening.

Psychological impact

  • Living with a chronic condition like G6PD deficiency can cause anxiety, stress, and feelings of isolation. Additionally, the constant need for vigilance and avoidance of triggers can affect quality of life.

Important notes

  • These complications are not inevitable and can be significantly reduced with proper management and early diagnosis.
  • The severity of potential complications heavily depends on the individual’s G6PD variant, adherence to management strategies, and access to healthcare.
  • Early diagnosis, proactive avoidance of triggers, regular checkups, and adherence to treatment plans are crucial for preventing or minimizing long-term complications and ensuring a healthy life with G6PD deficiency.

Is cetirizine safe for G6PD deficiency?

The safety of cetirizine for individuals with G6PD deficiency is a complex issue with varying opinions and ongoing research. Here’s a breakdown of what we know so far:

Potential Concern

  • Cetirizine belongs to the antihistamine class, some of which are known triggers for hemolytic episodes in G6PD individuals. Examples include:
    • Trimeprazine: This antihistamine has been widely documented to cause hemolysis in G6PD-deficient individuals.
    • Dapsone: While primarily used for leprosy, it also has antihistamine properties and can trigger hemolysis in G6PD patients.

Limited Evidence

  • No clear consensus: Despite being an antihistamine, cetirizine is not explicitly listed as a contraindicated medication for G6PD deficiency in major drug reference databases like MIMS (Malaysia) or the G6PD Deficiency Association website.
  • Limited studies: Research specifically analyzing the safety of cetirizine in G6PD patients is scarce.

Reasons for Potential Safety

  • Different mechanism: Cetirizine, unlike trimeprazine and dapsone, exerts its antihistamine effect through a different mechanism that might not directly affect red blood cell membranes, potentially reducing the risk of hemolysis.
  • Individual variability: G6PD deficiency severity and individual sensitivity to triggers vary greatly. Some individuals with mild G6PD deficiency might tolerate cetirizine without issues, while others might be more susceptible.


  • Consult your doctor: Discussing your G6PD deficiency with your doctor before taking cetirizine is crucial. They can consider your individual risk factors, medical history, and potential alternatives to ensure your safety.
  • Start with low doses: If your doctor deems cetirizine appropriate, consider starting with a low dose and monitoring for any adverse reactions.
  • Be aware of symptoms: Pay close attention to any potential signs of hemolysis like fatigue, jaundice, dark urine, or abdominal pain. If you experience any of these symptoms, stop taking cetirizine and seek medical attention immediately.
  • Alternative options: If you’re concerned about potential risks, discuss alternative antihistamines considered safe for G6PD individuals with your doctor.

Disclaimer: This article is intended for informational purposes only and is specifically targeted towards medical students. It is not intended to be a substitute for informed professional medical advice, diagnosis, or treatment. While the information presented here is derived from credible medical sources and is believed to be accurate and up-to-date, it is not guaranteed to be complete or error-free. See additional information.


  1. Anemia: Diagnosis and Treatment (Willis, 2016).
  2. Management of Anemia: A Comprehensive Guide for Clinicians (Provenzano et al., 2018)
  3. Goldberg S, Hoffman J. Clinical Hematology Made Ridiculously Simple, 1st Edition: An Incredibly Easy Way to Learn for Medical, Nursing, PA Students, and General Practitioners (MedMaster Medical Books). 2021.
  4. Luzzatto, L., Mehta, A. and Vulliamy, T. (2001) Glucose 6-Phosphate Dehydrogenase Deficiency. In: Scriver, C.R., Beaudet, A.L., Sly, W.S. and Valle, D., Eds., The Metabolic and Molecular Bases of Inherited Disease, 8th Edition, McGraw-Hill, New York, 4517-4533.
  5.  Herz F, Kaplan E, Scheye ES. Diagnosis of erythrocyte glucose-6-phosphate dehydrogenase deficiency in the negro male despite hemolytic crisis. Blood 1970;35:953-954. 
  6. Gautam, Keyoor. (2016). Glusoce-6-phosphate dehydrogenase- History and diagnosis. Journal of Pathology of Nepal. 6. 1034. 10.3126/jpn.v6i12.16260.

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