What is a Homocysteine Test?

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  • Written By: Jacquelyn Gilchrist
  • Edited By: Michelle Arevalo
  • Last Modified Date: 03 November 2019
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A homocysteine test measures the levels of homocysteine, an amino acid, in a person’s blood. High levels of this substance are linked to an elevated risk of stroke and coronary heart disease. It may also promote damage to the arteries and encourage blood clots.

This test may be recommended for patients with a family history of heart disease, as well as those who have suffered from a stroke or deep vein thrombosis, which is a condition caused by blood clots. A homocysteine test is a diagnostic tool that can help a doctor evaluate the patient’s risk for medical problems. It can also diagnose vitamin B deficiencies, which can cause fatigue and weakness. A homocysteine test may also be recommended for malnourished patients, alcohol and drug addicts, and the elderly, because these patients may be less able to absorb vitamin B12.

In addition, a homocysteine test may be performed on a baby by testing both the urine and the blood. This is often done to diagnose homocystinuria. This is a rare, inherited disorder in which the patient lacks a specific enzyme necessary for converting food into energy.


To prepare for the homocysteine test, the patient should inform his doctor of any medications or supplements he is taking. He may need to stop taking certain medications for a period of time before the test. The patient should also avoid consuming food and liquids, with the exception of water, for a minimum of eight hours prior to the test.

The doctor or nurse drawing the blood will disinfect an area on the upper arm before performing the homocysteine test. An elastic band will be wrapped around the arm to make the veins easier to locate, which facilitates needle insertion. The needle will then be inserted into the vein and a tube will be attached for collecting the blood. When enough blood has been drawn, the needle will be removed and a bandage will be applied to the area.

The test results will often be available in about 24 hours. If the homocysteine values are higher than normal, patients should bear in mind that this does not always indicate a disease. Men typically have higher values than women, and older patients usually have higher values than those who are young. High homocysteine levels could also be caused by excessive alcohol consumption. If the levels are lower than expected, this could be caused by regular vitamin intake or by certain medications.

A homocysteine test can perform a valuable diagnostic service for patients. The risks of taking this test are minimal. Patients may have a bruise at the injection site. Some people may experience a swollen vein, which can often be alleviated with warm compresses. Those who have a bleeding disorder, as well as patients who take blood-thinning medications, may experience bleeding at the injection site, and should consult with their doctors about any necessary precautions prior to the test.



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