What G6PD Means in Your 23andMe Raw Data
G6PD in your 23andMe raw data is a flag for an inherited enzyme deficiency, not a diagnosis. A normal raw file can still miss it.
In your 23andMe raw data, G6PD refers to a set of markers in the G6PD gene, which sits on the X chromosome. A flagged result can point towards glucose-6-phosphate dehydrogenase deficiency, the most common inherited enzyme deficiency worldwide. It is not a diagnosis by itself, and a raw file that looks normal does not rule the condition out.
What does G6PD mean in my 23andMe raw data?
Your raw file stores single-letter genotypes at specific positions in and around the G6PD gene. These positions are not the whole gene. They are a handful of known variants that appear on the chip 23andMe used to test you. Depending on the chip version, a search for G6PD may show rsIDs such as rs1050828, rs1050829 or rs5030868. Not every file contains every one of these. If a report says something like "G6PD decreased function" or "fava bean risk variant detected", it means the software found one of those tested variants in your file.
In the free HealthOS report, the G6PD line is: whether fava beans and certain drugs are safe for you. That is a useful plain-language summary, but it inherits the same limit as every raw DNA interpretation: it can flag a risk, not measure your enzyme activity today.
| Raw DNA file | G6PD enzyme assay | |
|---|---|---|
| What it reads | Known variant letters only | Enzyme activity in red cells |
| Strengths | Fast, no blood draw, flags common variants | Diagnoses deficiency and severity |
| Blind spots | Misses rare variants, cannot see X-inactivation in women | Can look normal right after a haemolytic episode |
Scroll the table sideways for the rest →
A raw file flags known variants. An enzyme assay measures current function.
The mechanism: why a small enzyme decides whether a red cell survives
G6PD stands for glucose-6-phosphate dehydrogenase. The enzyme sits at the start of the pentose phosphate pathway, which produces NADPH. Red blood cells use NADPH to keep glutathione in its reduced form. Reduced glutathione is the cell's main defence against oxidative damage.
A red cell has no nucleus and no mitochondria, so it cannot make new enzyme once it leaves the bone marrow. If G6PD activity is low, the cell has a smaller buffer against oxidant stress. When a trigger arrives, such as certain foods, drugs or a serious infection, the cell cannot regenerate enough reduced glutathione. Haemoglobin oxidises, forms clumps called Heinz bodies, and the spleen tears the damaged red cells apart. That process is acute haemolysis.
The result is anaemia that can develop quickly. Urine goes dark from free haemoglobin. People often notice back pain, jaundice, fatigue and a sudden drop in energy. The timing matters because it is not instant: symptoms usually appear within 24 to 72 hours after a trigger.
Fava beans, drugs and the 24 to 72 hour window
Fava beans, also called broad beans, contain oxidant compounds called divicine and isouramil. For someone with low G6PD activity, eating them can cause haemolysis. The name favism exists because the link between fava beans and sudden anaemia has been known for centuries, long before the gene was found.
The drug list is not random. The classic high-concern drugs include dapsone, primaquine, nitrofurantoin, sulfamethoxazole and methylene blue. Some infections themselves, especially sepsis, can tip a deficient person into haemolysis even without a drug. Mothballs with naphthalene are another exposure worth knowing about.
A raw file that flags a G6PD variant does not mean every one of those triggers will harm you. G6PD deficiency has grades. Some people have very low enzyme activity and react to modest amounts. Others have intermediate activity and may only react to high doses or severe illness. That is why this is a doctor-confirmation situation, not a self-diagnosis situation.
Why a normal raw file can still hide a problem
The most dangerous mistake is to open a raw file, see no G6PD variant listed, and decide fava beans and high-risk drugs are completely safe for you. That conclusion goes beyond what the data can support.
A consumer chip tests a few common G6PD positions. There are many more known variants, and some are rare or specific to particular populations. If your variant is not on the chip, the raw file says nothing about it. Women face an extra layer. The G6PD gene is on the X chromosome. A woman with one affected copy and one normal copy may have normal-looking raw data or a heterozygous call, but X-inactivation in her red cells can skew enzyme activity either way. The raw genotype cannot tell you which X is active in enough cells to matter.
There is also a lab timing problem. After a haemolytic episode, the older, most deficient red cells are destroyed first. The surviving young red cells often have higher G6PD activity. A normal enzyme result drawn too soon after a crisis can be falsely reassuring. This is a well-known limitation, and doctors often repeat the enzyme assay weeks later if the story still points to G6PD deficiency.
The test that actually settles it
If your raw file flags G6PD, or if you had a reaction to fava beans or a suspect drug, the test to ask about is a quantitative G6PD enzyme activity assay. It measures how much working enzyme your red cells have right now. That is different from another DNA test, because it captures the current functional state, including the effect of X-inactivation in women.
Ask about: - a quantitative G6PD enzyme activity assay - a reticulocyte count and bilirubin if done soon after a suspected episode - a repeat enzyme assay a few weeks after a crisis, because young red cells can temporarily raise activity
A doctor may also order a reticulocyte count or bilirubin to see whether your body is replacing red cells and clearing haemoglobin faster than usual after a suspected episode. Those pieces together, enzyme activity plus recent blood markers, give a much firmer answer than any raw file ever will.
A G6PD raw result is a flag, not a diagnosis. It says "check this properly" rather than "do not ever eat fava beans".
The download steps for 23andMe, on the page itself.
The short version: what is worth acting on, first.
If you already have a raw file from 23andMe, AncestryDNA, MyHeritage or a whole-genome VCF, the free DNA tool at https://healthosx.com/dna reads the G6PD markers in your browser, with no account needed for the DNA story, and reports whether fava beans and certain drugs are safe for you. It does not sequence the full G6PD gene and it does not replace an enzyme assay. When a G6PD marker is in play, the tool can show whether fava beans and certain drugs are flagged for you. For other genes, the free report only covers its listed traits.
New to raw DNA files? Start with the full guide: How to Download & Analyze Your 23andMe Raw Data Free
Written by
HealthOS Research