A homocysteine test is a blood test. It measures the amount of homocysteine, an amino acid in the body. The test is often used to diagnose vitamin B6, B9 or B12 deficiency. People with elevated homocysteine may have a higher risk for cardiovascular disease. In newborns, homocysteine testing can help diagnose a rare condition called homocystinuria.
A homocysteine test is a blood test that measures the amount of an amino acid called homocysteine in your body.
Homocysteine is a chemical that exists in small amounts in your blood. Vitamins B6, B9 and B12 help break down homocysteine, changing it into other substances your body needs. This process should leave behind very small levels of homocysteine in your blood.
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A homocysteine test often helps healthcare providers:
Homocysteine testing also may be part of newborn screening. It can identify a rare inherited condition called homocystinuria. The disorder means your body can’t process certain amino acids.
Your healthcare provider may order a homocysteine test if they suspect you aren’t getting enough vitamin B. Symptoms of a vitamin B deficiency may include:
A healthcare provider such as a nurse, doctor, phlebotomist or laboratory technician takes a blood sample for the test. Then, staff in a laboratory measure the level of homocysteine in the blood.
Your healthcare provider will give you specific instructions for the test. You may have to fast for eight to 12 hours. That means you shouldn’t eat or drink anything besides water.
You should also tell your healthcare provider about any prescription or over-the-counter medications you take, including supplements. They may affect the results of homocysteine testing.
It takes only a few minutes to collect your blood. In an office, clinic or lab, a healthcare provider will:
Your healthcare provider may ask you to keep the bandage on for a few hours. You may also need to avoid exercise for a few hours after the blood test.
Blood tests are very safe and involve little risk. You may have a small bruise where the needle went into the skin. Rarely, the vein may swell. Warm compresses can help.
Homocysteine test results are usually available in a day or two, depending on the lab.
Normally, your homocysteine should be less than 15.1 µmol/L. What’s considered normal may differ slightly from lab to lab.
Your healthcare provider will talk to you about the results and what they mean for you. High homocysteine might mean that you:
However, higher homocysteine levels don’t necessarily mean you have a medical condition. Your healthcare provider will consider many factors besides homocysteine level to make decisions about your health, such as:
A note from Cleveland Clinic
A homocysteine test is a simple blood test. A high homocysteine level may indicate a vitamin deficiency, higher risk for cardiovascular disease or another health condition. Your healthcare provider will talk to you about your results, other important factors and what it all means for you.
Last reviewed by a Cleveland Clinic medical professional on 02/02/2022.
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