What is homocysteine on a blood test?
Homocysteine is an amino acid your body produces and then has to clear.
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The short answer
Homocysteine is an amino acid your body produces and then has to clear. Clearing it needs vitamin B12, folate and vitamin B6. When any of those runs short, homocysteine rises. Raised levels are associated with cardiovascular and cognitive risk, and it's one of the few markers where a high result points directly at something you can do about it. At Epicentre it's R752.
What does Homocysteine measure?
Your body makes homocysteine constantly as a step in processing the amino acid methionine, which comes from protein in your diet. It's meant to be converted onwards almost immediately, either recycled back into methionine or turned into something else entirely.
Both of those exits depend on B vitamins. The recycling route needs B12 and folate. The other route needs B6. When any of them is in short supply, the conversion slows and homocysteine accumulates.
That's what makes it useful. Most markers tell you something is wrong. This one also suggests where to look.
Not sure whether you need this or something broader? Tell us what you are trying to find out.
Ask us on WhatsAppSee all 102 markersWhat does a high or low Homocysteine mean?
Before reading much into either, remember how reference ranges work. They are built so that about 95% of healthy people fall inside them, so roughly 1 in 20 normal results sits outside by definition. The pattern across related markers matters far more than any single value.
What else affects Homocysteine?
- B vitamin status
- The main one, and the reason the test is worth doing. B12, folate and B6 are all required to clear it.
- Kidney function
- Homocysteine is cleared by the kidneys, so reduced filtration raises it independently of your vitamins.
- Genetics
- Common variants in the MTHFR enzyme reduce how efficiently folate is processed. This is heavily discussed online and often overstated, but it's real and it affects interpretation.
- Thyroid status
- Untreated hypothyroidism raises homocysteine.
The functional view
Homocysteine is the marker functional medicine points at when it argues that a standard panel measures outcomes while a functional panel measures processes.
A standard workup might measure B12 and find it inside range. Homocysteine asks a different question: is there enough B12 for the job it's actually doing? Someone can have a B12 result at the bottom of the normal range and a raised homocysteine, which tells you the supply is technically present but functionally inadequate.
It's also one of the few markers where the response is straightforward and cheap. If the cause is a B vitamin shortfall, that's addressable. Whether lowering homocysteine reduces cardiovascular events is less settled than the association itself, and a doctor should be the one deciding what to do about a raised result.
Where this marker sits in the bigger picture
Detoxification
How your body processes what it produces and clears what it doesn't need. Homocysteine is a by-product that has to be actively converted, and it builds up when that machinery is short of what it needs.
Every blood order at Epicentre comes back with a functional health report at no extra cost, showing each marker against an optimal band as well as the standard range, ranked by what needs attention. Functional optimal ranges are educational reference recommendations rather than diagnostic thresholds, they are not universally agreed, and a value inside a standard laboratory range is not a disease. The standard report is still the one your doctor works from.
Which markers is it read with?
Vitamin B12 R206 and folate R206 are the obvious pair, since they're the likeliest cause of a raised result. Red cell folate R694 if you want stores rather than recent intake. Creatinine R70 to rule out reduced clearance.
Which packages include Homocysteine?
Cheapest first.
Includes Homocysteine.
See what's included →R2,427Coeliac Essential PanelIncludes Homocysteine.
See what's included →R3,973Mental Health and Mood PanelIncludes Homocysteine.
See what's included →R4,584Functional Health AnalysisIncludes Homocysteine.
See what's included →R4,890PCOS Metabolic PanelIncludes Homocysteine.
See what's included →R5,231ODx Max PackageIncludes Homocysteine.
See what's included →Plus 2 more panels that include Homocysteine. See all packages.
Where can I test Homocysteine in South Africa?
All three open Monday to Friday, 08:30 to 16:00, closed on public holidays. Medical aid rates are roughly 20% higher than the cash rate and generally need a doctor's request with an ICD-10 code.
Basically
Homocysteine is R752 at Epicentre and you do not need a referral for it. It is a functional marker, which means a standard panel will not include it unless you ask. One result on its own rarely settles anything: what matters is the pattern with the markers it is read alongside, and what it has done since last time.
Frequently asked questions
What causes high homocysteine?
Most often a shortfall of vitamin B12, folate or vitamin B6, since all three are needed to clear it. Other causes include reduced kidney function, untreated hypothyroidism, smoking, heavy alcohol use, some medicines, and inherited variation in the enzymes involved, particularly MTHFR.
Is high homocysteine dangerous?
Raised homocysteine is associated with higher cardiovascular and cognitive risk in population studies. Whether lowering it with B vitamins reduces those events is less settled, and trials have given mixed results. Treat a raised result as a reason to look for a cause with your doctor rather than as a diagnosis.
What does MTHFR have to do with homocysteine?
MTHFR is an enzyme in the folate pathway, and common genetic variants make it work less efficiently, which can raise homocysteine. It's widely discussed online and frequently overstated. The variants are common, most people carrying them are entirely well, and a homocysteine measurement tells you more about what's actually happening than the genotype does.
Should I test homocysteine or just B12?
They answer different questions. B12 tells you how much is in your blood. Homocysteine tells you whether there's enough for the work it needs to do, which is why someone can have a B12 in the low-normal range and a raised homocysteine. Testing both, at R206 and R752, gives you the fuller picture.
Other markers explained
This page is general health information and not a medical diagnosis. Epicentre Aids Risk Management (Pty) Ltd, practice number 1117394, provides diagnostic laboratory testing: we do not diagnose, prescribe or treat, and results are intended to inform a consultation with your doctor. Medically reviewed by Dr Samantha Naidoo, MB ChB, FCP (SA), Medical Director. Prices are 2026 cash rates including 15% VAT and can change without notice.