Total homocysteine (hoe-moe-SIST-een)
This test measures levels of homocysteine in your blood. Homocysteine is a type of amino acid your body naturally makes. At high levels, homocysteine can damage the lining of arteries and encourage blood clotting. As a result, high levels may raise your risk for coronary artery disease, heart attacks, blood clots, and strokes.
Having low levels of vitamin B12 (cobalamin), vitamin B6 (pyridoxine), vitamin B2 (riboflavin) or vitamin B9 (folic acid, folate) can cause elevated levels of homocysteine. Thyroid disease, kidney disease, psoriasis, and some medications can also lower your homocysteine level. Certain genetic causes, such as homocystinuria, will also lead to high homocysteine levels.
You might have this test to determine whether you have coronary artery disease or are at higher risk for this problem. You may also have this test to check for low levels of vitamin B12 or folate, which is another name for folic acid. In addition, you may be tested to see whether treatments for high homocysteine – such as nutritional changes, folic acid, or vitamin B supplements – are working to lower your homocysteine levels.
Your levels of vitamin B6, vitamin B12, and folate may also be measured when you have a homocysteine test.
A result for a lab test may be affected by many things, including the method the laboratory uses to do the test. If your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
The normal range of homocysteine levels for people up to age 30 is 4.6 to 8.1 micromoles per liter (mcmol/L). Between ages 30 and 59, normal ranges are 6.3 to 11.2 mcmol/L for men and 4.5 to 7.9 mcmol/L for women. After age 59, the normal range is 5.8 to 11.9 mcmol/L.
Higher levels could point to a B vitamin deficiency and a higher risk for coronary artery disease.
The test requires a blood sample, which is drawn through a needle from a vein in your arm.
Taking B vitamin supplements can affect results of a homocysteine test.
Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, and a sense of lightheadedness. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.
No special steps are necessary to prepare for this test.