In brief
An amino acid. Vitamin B12, folate and vitamin B6 help the body break it down, so a high level can be a sign of low B vitamins.
- Reference ranges for homocysteine vary between laboratories in Australia, so check the range on your own report.
- Vitamin B6 deficiency is a less common cause of a high homocysteine level.
- Ask your doctor whether you need to fast or stop any foods or supplements before the test.
How it works
A homocysteine test is most often used to assess vitamin B12, folate and B6 levels. Other causes of a high level include kidney disease, certain medicines and smoking. Homocystinuria is a rare inherited condition in which the body cannot process homocysteine properly, which increases the risk of dangerous blood clots.
Homocysteine testing is not routinely recommended for assessing heart disease risk, and lowering homocysteine has not been shown to reduce the risk of heart attack or stroke, according to Pathology Tests Explained. Folic acid supplements lower homocysteine levels but do not directly lower the risk of heart disease.
Connections
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Homocysteine is linked with
- Coronary heart disease Contested
Lowering homocysteine has not been shown to reduce the risk of heart attack or stroke, and testing is not routinely recommended to assess heart risk.
Homocysteine is controlled by
Folate and vitamin B12 are needed to turn homocysteine into methionine.
Sources: NIH Office of Dietary Supplements, Folate: fact sheet for health professionals; NIH Office of Dietary Supplements, Vitamin B12: fact sheet for health professionals
Lab tests
Sources
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Summarised from Pathology Tests Explained and the NIH Office of Dietary Supplements. Sources read on 13 October 2026. General education only, not medical advice. Spotted a mistake? Please tell us through the HuBu-Intel contact page.