Test Quick Guide

The homocysteine blood test measures the amount of homocysteine in your body. Typically, this test is used to diagnose a vitamin B6, B9, B12, or folic acid deficiency. A lack of these important vitamins increases homocysteine and can put you at a higher risk of cardiovascular disease. However, this test can also be ordered for newborns to diagnose a rare inherited disorder known as homocystinuria.

About the Test

Purpose of the test

The homocysteine test may be used in the following ways:

  • To diagnose a vitamin B12 or folate deficiency. The homocysteine concentration may be elevated before B12 and folate tests become abnormal. Some health care practitioners may recommend homocysteine testing in malnourished individuals, the elderly (who often absorb less vitamin B12 from their diet), and individuals with poor nutrition, such as drug or alcohol addicts.
  • As a general screening for people at high risk for heart attack or stroke. It may be useful if you have a family history of coronary artery disease but no other known risk factors, such as smoking, high blood pressure, or obesity. But the exact role homocysteine plays in the progression of cardiovascular disease has not been established, so the utility of the screening test is questioned. Routine screening for hyperhomocysteinemia, such as for total cholesterol, is not recommended.

What does the test measure?

The homocysteine test measures your blood levels of this naturally occurring amino acid that serves in the body as an intermediate in the metabolism of methionine and cysteine. The amino acid is typically broken down in the blood into other substances your body needs. So elevated levels usually indicate a deficiency of vitamin B12, B6, or folic acid because these vitamins help the body process homocysteine.

When should I get this test?

This test may be ordered when a health practitioner suspects you may have a vitamin B12 and/or folate deficiency. Signs and symptoms are initially subtle and nonspecific. If you have an early deficiency, you may be diagnosed before experiencing any overt symptoms. Other affected people may experience a variety of mild to severe symptoms that can include:

  • Diarrhea
  • Dizziness
  • Fatigue, weakness
  • Loss of appetite
  • Paleness
  • Rapid heart rate
  • Shortness of breath
  • Sore tongue and mouth
  • Tingling, numbness, and/or burning in the feet, hands, arms, and legs (B12 deficiency can cause neuropathy)

Homocysteine testing may be ordered as part of assessing your risk of cardiovascular disease, depending on the individual’s age and other risk factors. It may also be ordered following a heart attack or stroke to help guide treatment.

Finding a Homocysteine Test

How to get tested

Homocysteine testing is usually performed at a doctor’s office or another medical setting like a hospital or lab.

Can I take the test at home?

As a test requiring a blood draw, it is impossible to self-administer a homocysteine test at home. But there may be mobile laboratories in your area which can go to your home to perform the blood draw, then deliver the sample to a laboratory of your choice.

How much does the test cost?

The cost of a homocysteine test will vary depending on factors such as where the test is done and whether you have health insurance. When ordered by a doctor, insurance typically covers the test, although you may have to pay a copay or deductible. Your doctor’s office, lab, and health plan can provide information about any out-of-pocket costs that may be your responsibility.

Taking the Homocysteine Test

The homocysteine test requires a blood sample, usually taken from your arm in a doctor’s office, health clinic, hospital, or lab. A blood sample is typically taken from the baby’s heel for screening tests in newborns.

Before the test

Usually, no special preparation is required for a homocysteine test. Your doctor will tell you if you must stop taking any medications or supplements before the test.

During the test

A blood sample is taken from a vein in your arm. The person taking the sample may tie a band around your upper arm and will clean the area where the needle will be inserted into your skin. A small amount of blood is drawn into a tube. You may feel a slight sting when the needle enters your skin.

The process of taking a blood sample usually takes just a few minutes.

After the test

At a doctor’s office or lab, you will be asked to apply gentle pressure to the site with a bandage or a piece of gauze after the needle is withdrawn. This will help stop bleeding and may prevent bruising. Next, the site will be bandaged. You may resume your normal activities following the test.

A blood draw is a very low-risk procedure. You may have slight bruising at the site where the blood sample was taken.

Homocysteine Test Results

Receiving test results

The doctor who ordered your homocysteine test may share the results with you, or you may be able to access them through an online patient portal. Homocysteine results are usually available within a few business days.

Interpreting test results

In cases of suspected malnutrition, vitamin B12 or folate deficiency, homocysteine levels may be elevated. If an individual does not get enough B vitamins and/or folate through diet or supplements, the body may not be able to convert homocysteine to other forms that can be used. In this case, the level of homocysteine in the blood can increase.

Studies from the mid- to late-1990s suggested that people with elevated homocysteine levels have a much greater risk of heart attack or stroke than those with average levels. Investigating the link between high homocysteine levels and heart disease remains an active area of research.

At present, however, the use of homocysteine levels for risk assessment of cardiovascular disease (CVD), peripheral vascular disease, and stroke is uncertain, given that several trials investigating folic acid and B vitamin supplementation indicate no benefit or lowering of CVD risk.

Additionally, a 2012 study of multiple datasets, including 50,000 people with coronary heart disease, called the potential for a cause-and-effect relationship between homocysteine levels and heart disease into question.

A 2015 review of studies concluded that although there is a relationship between homocysteine and CVD, there is other evidence that precludes homocysteine in being considered a biomarker for the disease. The American Heart Association (AHA) does acknowledge the relationship between homocysteine levels and heart attack/stroke survival rates but doesn’t consider elevated homocysteine an independent risk factor for CVD.

While the AHA does not recommend the widespread use of folic acid and B vitamins to reduce risk of heart attack and stroke, it does promote a balanced, healthy diet. It advises health care practitioners to consider overall risk factors and diet in managing cardiovascular disease.

You may want to ask your doctor the following questions:

  • Could any medications I may be taking affect my homocysteine level?
  • What are some good sources of folic acid and vitamins B6 and B12?
  • Are there any follow-up tests I should do?


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