Glucose-6-phosphate dehydrogenase (G6PD) deficiency is widely recognised as one of the more common enzyme deficiencies worldwide, yet many people in London and across the UK remain unaware they carry it. A G6PD deficiency test can help identify whether your body lacks adequate levels of this critical enzyme — information that may be particularly important before starting certain medications. Understanding your G6PD status through a simple blood test can play a meaningful role in supporting informed conversations with your healthcare provider about medication safety.
At Walk In Clinic London, our nurse-led team provides convenient G6PD deficiency screening as part of our commitment to accessible, preventive health testing across the capital.
What Is G6PD Deficiency?
G6PD deficiency is an inherited genetic condition in which the body does not produce enough glucose-6-phosphate dehydrogenase, an enzyme that helps protect red blood cells from oxidative damage. Without sufficient G6PD, red blood cells can break down prematurely — a process known as haemolysis — particularly when exposed to certain triggers such as specific medications, infections, or foods.
Practical Insight: G6PD deficiency is typically inherited in an X-linked pattern, meaning it more commonly affects males, though females can also be carriers or, less frequently, affected.
Why Does G6PD Deficiency Matter for Medication Safety?
The relationship between G6PD deficiency and medication safety is a critically important one. Certain commonly prescribed drugs — including some antimalarials, antibiotics, and pain relievers — can trigger haemolytic episodes in individuals with low G6PD levels. Without prior knowledge of the deficiency, a person may unknowingly take a medication that could cause a significant reaction.
This is why screening for G6PD deficiency before starting new medications can be a valuable preventive step. A blood test result showing G6PD levels can help your prescribing healthcare professional make more informed decisions about which medications may be appropriate for you.
Medications That May Be Affected by G6PD Status
The following categories of medication have been associated with potential adverse reactions in individuals with G6PD deficiency:
- Antimalarials — such as primaquine and chloroquine
- Certain antibiotics — including nitrofurantoin, sulphonamides, and dapsone
- Analgesics — such as high-dose aspirin in some cases
- Certain chemotherapy agents
- Rasburicase — used in some oncology settings
- Methylene blue — used in specific clinical scenarios
Practical Insight: This list is not exhaustive. If your G6PD test results indicate a deficiency, sharing this information with your prescribing healthcare professional can support safer medication choices.
Who Should Consider a G6PD Deficiency Test?
While G6PD deficiency can affect anyone, certain groups may particularly benefit from screening. You may wish to consider a G6PD blood test if you:
- Have a family history of G6PD deficiency or favism
- Are of African, Mediterranean, Middle Eastern, or South Asian heritage — populations where the condition is more prevalent
- Are planning to travel to a malaria-endemic region and may require antimalarial medication
- Have experienced unexplained episodes of anaemia or jaundice
- Are starting a new medication that is known to interact with G6PD deficiency
- Are a prospective parent and wish to understand your carrier status
- Have experienced dark-coloured urine, fatigue, or pallor after taking certain medications or eating fava beans
Practical Insight: London's richly diverse population means that G6PD deficiency screening can be especially relevant across many of the city's communities. Being proactive about testing may support better-informed healthcare decisions.
G6PD Deficiency: UK Prevalence and London Context
In the UK, G6PD deficiency is estimated to affect around 1 in 10 males of African descent and approximately 1 in 50 males of Mediterranean descent. Given London's multicultural demographic, awareness of the condition — and the availability of accessible screening — is particularly important.
Unlike some countries where newborn G6PD screening is routine, the UK does not include G6PD testing in its standard newborn screening programme. This means many individuals may reach adulthood without knowing their status, potentially discovering it only when a medication triggers an adverse reaction.
If you are interested in the dietary aspects of G6PD deficiency, our guide to favism and G6PD deficiency explores this in more detail.
How Often Should You Get Tested?
G6PD deficiency is a genetic condition, which means your enzyme status does not change over time. In most cases, a single screening test is sufficient to determine whether you have adequate G6PD levels.
However, there are situations where retesting or initial testing may be particularly relevant:
| Scenario | Testing Recommendation |
|---|---|
| No prior G6PD test, heritage-linked risk | Consider a one-time screening test |
| Family history of G6PD deficiency | A single baseline test is generally sufficient |
| Pre-travel (antimalarial medication planned) | Test before starting medication if status is unknown |
| Unexplained haemolytic episodes | Discuss testing with your healthcare provider |
| Recent haemolytic episode | Retesting may be advised, as results during active haemolysis can sometimes appear falsely normal |
| Previous normal result, no new risk factors | Repeat testing is generally not required |
Practical Insight: If you have been tested during an active haemolytic episode, results can sometimes underestimate the severity of deficiency. Your healthcare provider may recommend a follow-up test once you have recovered.
What Do G6PD Test Results Mean?
A G6PD test measures the activity level of the enzyme in your red blood cells. Results are typically reported as enzyme activity in units per gram of haemoglobin (U/g Hb).
- Normal G6PD levels — Enzyme activity falls within the expected reference range. This generally suggests that the medications commonly associated with G6PD-related reactions can be considered by your prescribing healthcare professional without this specific concern.
- Reduced G6PD levels (deficient) — Enzyme activity is below the normal range. This result may indicate G6PD deficiency, which can be relevant when making decisions about certain medications, dietary considerations, or managing other health conditions.
- Intermediate levels — Sometimes seen in female carriers. This may suggest partial deficiency and can still be clinically relevant in certain circumstances.
It is important to note that Walk In Clinic London provides testing and reporting only. We recommend sharing your results with an appropriate healthcare professional who can interpret them within the context of your full medical history and advise on any next steps.
Practical Insight: Your G6PD test result is a valuable piece of your health profile. Keeping a record of it — particularly if you are planning travel or starting new medications — can support ongoing conversations with your healthcare providers.
NHS vs Private G6PD Testing in London
| Factor | NHS | Private (Walk In Clinic London) |
|---|---|---|
| Availability | Usually requires GP referral and clinical indication | Available as a walk-in service without referral |
| Waiting time | May involve waiting for a GP appointment and lab processing | Same-day appointments typically available |
| Accessibility | Dependent on GP capacity and local pathways | Centrally located in London for easy access |
| Cost | Free at point of care (if clinically indicated) | Fee applies — please visit our website for current pricing |
| Results turnaround | Variable | Typically faster turnaround |
Both NHS and private testing pathways provide clinically validated results. The choice between them often depends on individual circumstances, including urgency, convenience, and whether a GP has identified a clinical need.
For details on our available health screening services, please visit our website or contact our clinic directly.
The Walk In Clinic London Approach
Our nurse-led clinic in central London offers a welcoming, straightforward environment for blood testing and health screening. We provide:
- No appointment necessary — walk-in availability for your convenience
- Professional, nurse-led service — experienced clinical staff conduct all testing
- Fast, confidential results — delivered securely so you can share them with your chosen healthcare professional
- Wide range of blood tests — including enzyme, haematology, and general wellness panels. Learn more about our G6PD testing in London
We focus exclusively on testing and reporting. For interpretation of results and any clinical advice, we always encourage our patients to consult with an appropriate healthcare professional.
Frequently Asked Questions
What is a G6PD deficiency test?
A G6PD deficiency test is a blood test that measures the activity level of the glucose-6-phosphate dehydrogenase enzyme in your red blood cells. It can help identify whether you have adequate enzyme levels or whether a deficiency may be present, which can be relevant for medication safety and overall health awareness.
Why is G6PD deficiency important for medication safety?
Certain medications — including some antimalarials, antibiotics, and analgesics — can trigger the breakdown of red blood cells in people with G6PD deficiency. Knowing your G6PD status before starting such medications may help your healthcare provider make more informed prescribing decisions.
Who is most at risk of G6PD deficiency?
G6PD deficiency is more prevalent among individuals of African, Mediterranean, Middle Eastern, and South Asian heritage. Males are more commonly affected due to the X-linked inheritance pattern. However, females can also be carriers or affected, particularly if both parents carry the gene variant.
Can I get a G6PD deficiency test in London without a GP referral?
Yes. At Walk In Clinic London, you can access G6PD deficiency screening as a walk-in service without the need for a GP referral. Our nurse-led team is available to carry out the blood test at your convenience.
How long does it take to get G6PD test results?
Turnaround times can vary, but private clinics such as Walk In Clinic London typically provide results faster than standard NHS pathways. Please contact our clinic or visit our website for current expected timescales.
Is G6PD deficiency testing a one-time test?
In most cases, yes. Since G6PD deficiency is a genetic condition, your enzyme status remains constant throughout your life. A single screening test is usually sufficient, though retesting may occasionally be recommended if the initial test was conducted during an active haemolytic episode.
What foods should people with G6PD deficiency be aware of?
Fava beans (broad beans) are the most well-known dietary trigger for haemolytic episodes in individuals with G6PD deficiency. Some people may also react to certain food additives or herbal preparations. If your test suggests a deficiency, seeking medical advice on dietary considerations may be helpful.
Can G6PD deficiency be cured?
G6PD deficiency is a lifelong genetic condition and there is currently no cure. However, awareness of the condition — gained through screening — can help individuals and their healthcare providers avoid known triggers, supporting better long-term health management.
Should I get tested for G6PD deficiency before travelling?
If you are planning to travel to a region where antimalarial medication may be recommended, and you do not know your G6PD status, testing beforehand can be a sensible precaution. Certain antimalarials are contraindicated in G6PD-deficient individuals, and your travel health advisor or prescriber would benefit from having this information.
Does Walk In Clinic London offer other blood tests alongside G6PD screening?
Yes. We offer a comprehensive range of blood tests and health screenings, including general wellness panels, sexual health testing, and specific biomarker assessments. Visit our website for the full range of services available.
Supporting Your Health Decisions Through Screening
Understanding your G6PD status is a straightforward yet potentially impactful step in managing your long-term wellbeing — particularly if you belong to a higher-prevalence group or anticipate starting medication that may interact with the enzyme. A simple blood test can provide clarity and equip you with information to share with your healthcare providers.
At Walk In Clinic London, we are committed to making preventive health screening accessible, convenient, and professionally delivered. Whether you are considering a G6PD deficiency test or exploring broader health check options, our experienced nurse-led team is here to support your journey toward informed, proactive health management.
Medical Disclaimer
This article is for educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Walk In Clinic London provides testing and reporting services only.
Written Date: 23 March 2026
Next Review Date: 23 March 2027
