Homocysteine

Heart & blood vessel risk

Homocysteine is an amino acid made when the body breaks down protein. The body needs vitamin B12, folate and vitamin B6 to clear it, so levels rise when these vitamins are low. A high homocysteine is also linked with a higher risk of heart disease, stroke and blood clots, and can be caused by kidney disease or rare inherited conditions.

• To look for a lack of vitamin B12 or folate, for example with anaemia, numbness or memory problems
• In people who have had heart disease, a stroke or blood clots at a young age
• When a rare inherited condition that raises homocysteine is suspected
• To check the response to vitamin B12 or folate treatment

Fasting is needed before this test: drink only plain water for the fasting time shown on this page. If you take vitamin B12, folic acid or other B vitamin supplements, tell your doctor, as they can lower the result. Keep taking your usual medicines unless your doctor says otherwise.

Sample

Blood sample

How it works

The collector visits in the morning, while you are still fasting, and takes a small blood sample from a vein in your arm. Homocysteine can rise if blood is left standing before it is processed, which is why this sample is handled promptly.

Report

Within 2 days of collection.

Your report shows homocysteine next to the laboratory's range. A raised level often points to a lack of vitamin B12, folate or vitamin B6, and can also be seen with kidney disease, an underactive thyroid, smoking, some medicines and inherited conditions. It is linked with a higher risk of heart and blood vessel disease, but it is only one of many risk factors. Your doctor will interpret the result together with your vitamin levels and other tests.

One test: Homocysteine, from one blood sample.