Also Known As
MTHFR DNA testing
Formal Name
MTHFR DNA testing
This article was last reviewed on
This article waslast modified on 15 February 2023.
At a Glance
Why Get Tested?

To evaluate the cause of elevated homocysteine levels

When To Get Tested?

When you have elevated homocysteine levels

Sample Required?

A blood sample is obtained by inserting a needle into a vein in the arm.

Test Preparation Needed?

No test preparation is needed

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?

The methylenetetrahydrofolate reductase (MTHFR) gene oversees the production of the MTHFR enzyme. This enzyme changes one form of folate into another and is part of the process that converts homocysteine into methionine, an important building block for many proteins.

MTHFR testing detects two relatively common DNA sequence variants (single nucleotide polymorphisms, SNPs) in the MTHFR gene, C677T and A1298C. These SNPs result in changes in the DNA (or mutations) and are associated with increased homocysteine levels in the blood. Approximately 10% of the British population is homozygous for C677T. The prevalence is higher in those of Mediterranean and lower in those of African or Indian Asian descent. The rise in homocysteine within the bloodstream is worsened when the affected person is folate-deficient or if they have inherited multiple mutations.

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Common Questions
  • How is it used?

    The methylenetetrahydrofolate reductase (MTHFR) mutation test is used to detect two relatively common mutations in the MTHFR gene that are associated with elevated levels of homocysteine in the blood. It is not routinely performed within the UK.

    An MTHFR test is not recommended, nor homocysteine, in diagnostic testing for inherited high clotting risk, thrombophilia. There is also no role for testing is cardiovascular risk assessment either.

    Though the MTHFR test may be used to help determine the cause of elevated homocysteine, the value of measuring homocysteine levels outside of people presenting with homocystinuria is not clear. Homocystinuria is detected by the neonatal heel prick screen therefore most people born in the UK will have had homocystinuria excluded at birth.

  • When is it requested?

    The MTHFR test may very rarely be requested when a person has elevated homocysteine levels but not usually within the UK.

  • What does the test result mean?

    If a person has two copies (homozygous) of MTHFR C677T, or has one copy of C677T and one of A1298C, then it is likely that elevated homocysteine levels in that person are due to these inherited mutations, or that the mutations are contributing to them. Other, rarer MTHFR genetic mutations will not be detected with typical testing.

  • Is there anything else I should know?

    Besides MTHFR mutations, there are other causes of elevated homocysteine levels, including deficiency of vitamins B6, B12, and/or folate; these vitamins are required for homocysteine metabolism.

    MTHFR mutations are a rare cause of homocystinuria, a condition caused by a defective enzyme that disrupts methionine metabolism, leads to greatly increased amounts of homocysteine in the blood and urine, and causes a variety of complications. The most common cause of this condition is a deficiency in the cystathionine B-synthase (CBS) enzyme. The MTHFR mutations that cause homocystinuria are typically not detected by this test.

  • Who performs MTHFR testing?

    It is not offered in every laboratory. In most cases, your blood will be sent to a reference laboratory.

  • Can my MTHFR genes change?

    No, you inherit a copy of the gene from each of your parents and they will not change over time.

  • If I have the same MTHFR gene mutations as a relative, why is my homocysteine level significantly different?

    Even when two people have the same MTHFR mutations, the results are often different. Many things can affect homocysteine levels, including MTHFR enzyme activity, folate levels, and a person's health status.