Also Known As
Plasma Total Homocysteine
Urine Homocysteine
This article was last reviewed on
This article waslast modified on 9 November 2020.
At a Glance
Why Get Tested?

To find out if you are at high risk of a heart attack or stroke; 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 had a heart attack or stroke, particularly in the absence of traditional risk factors or as part of a cardiac risk assessment

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

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, sex, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

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 product of methionine metabolism, 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.

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Common Questions
  • How is it used?

    Homocysteine is sometimes used to help in the investigation of people who might be at high risk for heart attack or stroke. For example, it may be useful in patients who have a family history of coronary heart disease (CHD) but no other known risk factors.

    Occasionally, a doctor may also request a homocysteine test in the investigation of suspected vitamin B12 or folate deficiency.

  • When is it requested?

    Homocysteine may be requested as part of a cardiac risk assessment, depending on your age and other risk factors. It may also be used following a heart attack or stroke to help determine treatment.

  • What does the test result mean?

    At present, a direct correlation between homocysteine levels and heart attacks has not been established, but there does seem to be strong evidence of a relationship between homocysteine levels and heart attack/stroke survival rates.

    While earlier studies suggested that people who have elevated homocysteine levels have a much greater risk of heart attack or stroke than those with average levels, at present, the use of homocysteine levels for risk assessment of cardiovascular disease (CVD), is uncertain given that several trials investigating folic acid and B vitamin supplementation indicate no benefit or lowering of CVD risk. 

  • Is there anything else I should know?

    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 estrogen 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.

  • What are some good sources of folic acid and vitamins B6 and B12?

    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. People with high homocysteine levels also may benefit from taking multivitamins to supplement this amount.

  • Is there a difference in risk between men and women?

    Homocysteine levels in women increase after menopause, possibly due to decreased oestrogen production. Even so, the risk for women does not appear to increase with moderately-elevated levels.

  • Could any drugs I may be taking have an effect on my homocysteine level?

    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.