Homocysteine

Measures an amino acid metabolite whose level is affected by various factors.

To assess B12/folate metabolism and conditions linked to raised homocysteine.

1. Check in advance whether you need to fast or have your blood drawn at a specific time.
2. Agree on fasting and vitamin intake with the laboratory in advance. Tell staff about any B6/B12/folate supplements.
3. Before the blood draw, avoid unusually intense physical exercise unless your doctor has advised otherwise.
4. Tell your doctor and the laboratory staff about any medicines and dietary supplements you take.

There is no single rule. Whether you need to fast, and for how long, depends on the purpose of the test and the laboratory method; check in advance.

A specific time is generally not required. If your doctor has set a different time, follow those instructions.

• B6, B12 and folate supplements
• Kidney function
• Delayed separation of the sample from blood cells

Venous blood — serum or plasma, depending on the method

The sample is collected by a specialist. For homocysteine, timely separation of plasma/serum from the cells matters; processing time and temperature are set by the laboratory method.

Raised homocysteine may be linked to B12/folate deficiency, kidney function and other factors; on its own it does not identify the cause.

If your result is outside the reference interval, you have symptoms, or your condition changes, contact your doctor. If symptoms are severe or develop quickly, seek emergency care.

Prompt centrifugation of the sample is important: prolonged contact with cells can raise homocysteine.