Serum Homocysteine

Specimen Required

3-5cc Clotted Blood or Serum

Fasting Required

Purpose of the Test

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 this test is required

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.

What the Test Detects

This test measures the level of homocysteine in the blood. Homocysteine is a sulphur-containing amino acid that is normally present in very small amounts in all cells of the body. Homocysteine is a produced when methionine is metabolised, and methionine is one of the eleven “essential” amino acids (an essential amino acids must be derived from the diet since the body cannot make them). In healthy cells, homocysteine is quickly converted to other products.Folic acid (folate) is one of the “B” vitamins that is needed to metabolise homocysteine. Vitamin B12, another B vitamin, helps keep folate in its active form, allowing it to keep homocysteine levels low. People who are deficient in these vitamins may have increased levels of homocysteine.See MoreSee Less

Preparation for the Test

You may be instructed to fast for 10 to 12 hours prior to this test

Sample Requirements

A blood sample taken by needle from a vein in the arm

Additional Notes

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.

Selected Tests