Optimize
← All biomarkers
B-VitaminsHeart & Vascular

Homocysteine

Homocysteine is an amino acid your body clears with B-vitamins, rising when folate or B12 runs short.

What is Homocysteine?

Homocysteine is an amino acid formed when your body breaks down protein. Your body normally clears it again using folate, vitamin B12, and B6. When one of those vitamins runs short, homocysteine builds up and the blood level rises. That makes homocysteine a functional measure: it shows whether your B-vitamin system is actually working, not just how much vitamin sits in your blood. Test fasting for a reliable value. Always read it together with vitamin B12 and folate.

Why is Homocysteine relevant?

Homocysteine often rises before your B12 or folate level itself becomes abnormal. That makes it an early signal of an emerging deficiency — valuable for people at higher risk, such as vegans, older adults, and those on long-term acid-reducing medication or metformin. A raised value is also associated with a higher risk of heart and vascular disease. Whether it causes damage itself or mainly reflects an unfavourable profile is uncertain — but as a supporting marker alongside your lipids, it adds useful context.

Homocysteine high or low — what it means

Always read homocysteine together with vitamin B12 and folate — only then can you tell whether an elevation comes from a vitamin shortfall. If MMA is also measured: a raised MMA with raised homocysteine points specifically to a B12 deficiency, while a normal MMA fits more with a folate or B6 shortfall. Smoking, heavy coffee intake, and reduced kidney function can all raise the value. With an elevated result, the first step is usually folate and B12 supplementation (and B6 in smokers), with a repeat after 8–12 weeks to see whether it responds. If it stays high despite supplementation, kidney function and medication are the logical next things to check.

Homocysteine reference ranges

OptimalFavourable; often targeted in preventive medicine< 10 µmol/L
NormalAcceptable in healthy people; upper end slightly raised10 - 15 µmol/L
ElevatedCardiovascular risk factor; 15-30 = mild, 30-100 = moderate hyperhomocysteinemia> 15 µmol/L
MenCommonly used lab cutoff< 16.4 µmol/L
WomenCommonly used lab cutoff< 13.4 µmol/L

Cutoffs vary by laboratory and method. Test fasting (about 12 hours). The ‘normal’ value rises with age (roughly 5-10% per 10 years); some labs use < 65 years: < 15 and > 65 years: < 20 µmol/L.

Educational information only — not medical advice. Consult a healthcare professional for clinical decisions.

Read about our scientific approach →Read the guide: Energy →

Frequently asked questions

What is a normal homocysteine level?

Below 15 µmol/L is usually considered normal, and below 10 µmol/L is considered optimal. Between 10 and 15 µmol/L is acceptable in healthy people. Many labs use slightly different cutoffs for men (around < 16 µmol/L) and women (around < 13 µmol/L). Test fasting, as a recent meal affects the result.

What does a high homocysteine mean?

Above 15 µmol/L is considered elevated. The common classification is: 15-30 µmol/L mild, 30-100 µmol/L moderate, and above 100 µmol/L severe hyperhomocysteinemia. It usually reflects a functional shortfall of folate, vitamin B12, or B6, and is associated with a higher risk of heart and vascular disease. Smoking, heavy coffee intake, certain medications, and reduced kidney function can also raise the value.

When is an elevated homocysteine a concern?

A value above 15 µmol/L deserves further evaluation, especially with a familial cardiovascular profile or suspected B-vitamin deficiency. Always read homocysteine together with vitamin B12 and folate — only then can you tell whether an elevation comes from a vitamin shortfall. A low value, by contrast, is favourable and not a cause for concern.

How do I lower my homocysteine?

With an elevated value, supplementing folate and vitamin B12 (and B6 in smokers) often helps lower it. Cutting back on smoking and coffee also helps. Re-test after 8-12 weeks to see whether it responds. If it stays high despite supplementation, kidney function and medication are the logical next things to check.

Related biomarkers

Folate (vitamin B9)
Folate is a B vitamin your body needs for DNA synthesis, cell division and blood production.
Methylmalonic Acid (MMA)
Methylmalonic acid (MMA) is a metabolite that builds up when your cells run short on vitamin B12.
Vitamin B12
Vitamin B12 is a B vitamin your body needs for your nerves, DNA production, and blood formation.
Apolipoprotein B (ApoB)
ApoB is a protein on every harmful cholesterol particle, so it counts how many of those particles circulate in your blood.
C-Reactive Protein (CRP)
CRP is a protein your liver makes in response to inflammation, serving as a broad marker of inflammation in your body.
HDL Cholesterol
HDL is the 'good' cholesterol that carries excess cholesterol back to your liver.

Homocysteine is one of the biomarkers in the Optimize blood test. Book a blood draw at any of 238+ partner labs in the Netherlands, or upload your existing results in the app.

See the full test