Homocysteine Test

What is homocysteine?

Homocysteine is a chemical found in the blood that is produced when the amino acid methionine (a building block for proteins) is broken down. High levels are linked to an increased risk of heart disease. For more information on homocysteine and heart disease risk, see our homocysteine article in the risk factors section.

Who might have a homocysteine test?

Homocysteine testing may be useful if you or a family member have heart or blood vessel disease, but do not have any of the well-established risk factors such as smoking, high blood cholesterol, high blood pressure, obesity, or diabetes.

What does the homocysteine test entail?

Homocysteine is measured through a routine blood test. It not widely available, costs about $100, and is not currently covered by insurance. More rarely, your healthcare provider may order a methionine-load test, which measures homocysteine before and after you swallow 100 mg/kg of methionine (dissolved in orange juice). This test can diagnose homocysteine abnormalities in people at high risk for heart disease who have normal homocysteine levels when tested with the routine blood test.

What do the results of a homoscysteine test mean?

Homocysteine Blood Levels 1
Fasting Plasma Homocysteine Level (µmol/L*)
Moderately high16-30
Intermediately high31-100
Severely high>100
*µmol/L = micromoles of homocysteine per liter of blood

If you have high homocysteine levels, you have a higher risk of heart attack, stroke, and developing blood clots in the arteries and veins in the legs. However, there is no treatment plan for high homocysteine levels, since it has not been shown that lowering homocysteine cuts down you heart disease risk.1 For more info, see our homocysteine section.


1. Malinow MR, Bostom AG, Krauss RM. Homocyst(e)ine, diet, and cardiovascular diseases: a statement for healthcare professionals from the Nutrition Committee, American Heart Association. Circulation. Jan 5-12 1999;99(1):178-182.

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