Homocysteine
Note: this site is for informational purposes only. To view test results or book a test, use the NHS app in England or contact your GP.
The homocysteine test measures the level of homocysteine, a sulphur-containing amino acid, in the blood using a blood sample taken from a vein in the arm. It is used to help assess the risk of cardiovascular disease and to investigate conditions such as vitamin B12 or folate deficiency and disorders affecting blood clotting.
Why get tested?
To find out if you have a rare inborn error of metabolism (homcystinuria); also used to determine if you are folate-deficient or vitamin B12-deficient as blood homocysteine concentration can be raised in both conditions.
When to get tested?
If you have symptoms consistent with homocystinuria, for example dislocation of the lens of the eye or some blood clots, and all newborn babies are tested via heel prick in the newborn screening program. Rarely when vitamin B12 concentrations are borderline and suspicion is high that B12 deficiency is present homocysteine (or methylmalonic acid) can help prove tissue deficiency in the face of a normal blood concentration.
Sample required?
A blood sample taken by needle from a vein in the arm.
Test preparation needed?
You may be instructed to fast for 10 to 12 hours prior to this test.
Common questions
Homocysteine can be used to detect homocystinuria. The amino acid concentrations of methionine and homocysteine are measured in the blood, and sometimes urine, including in the blood spot from a newborn baby’s heel to detect and screen for this condition.
Occasionally, a doctor may also request a homocysteine test in the investigation of suspected vitamin B12 or folate deficiency.
Homocysteine is measured in all newborns in the UK who are tested as part of the newborn screening program. People affected with suspected homocystinuria and relatives may also be tested.
A high levels may infer vitamin deficiency or, very rarely, homocystinuria however many other factors can cause it to, for example kidney disease or a non-fasting specimen.
There is evidence of an association between homocysteine levels and cardiovascular disease e.g. heart attack/stroke. However reduction of homocysteine levels with B vitamins does not reduce the risk therefore there is no evidence that the homocysteine is causing the problem. Therefore measurement of homocysteine to asses cardiovascular risk, and treatment with folic acid for example, is not standard recommended care.
Homocysteine levels can increase with age, when a patient smokes, and with the use of drugs such as carbamazepine, methotrexate, and phenytoin. Homocysteine levels are lower in women than in men. Women’s concentrations increase after menopause, possibly due to decreased oestrogen production.
Homocystinuria is a rare inherited metabolic disorder characterised by an increased blood and urine concentration of homocysteine. Classical homocystinuria is due to a deficiency in cystathionine beta synthase (CBS). Affected individuals appear normal at birth but develop serious complications in childhood. Diagnosis and treatment started sufficiently early in life can effectively prevent or reduce the severity of these complications.
Green leafy vegetables and cereal grains are the main source of folic acid. Fruits and vegetables have significant amounts of vitamin B6, and vitamin B12 can be found in red meats, poultry, fish, and other seafoods.
Yes. There are numerous drugs that may either increase or decrease the amount of homocysteine in your body. You should always keep your doctor and pharmacist aware of any drugs, traditional or herbal, you are taking, since they may interfere with the test results.
Yes. There are numerous drugs that may either increase or decrease the amount of homocysteine in your body. You should always keep your doctor and pharmacist aware of any drugs, traditional or herbal, you are taking, since they may interfere with the test results.