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Homocysteine Blood Test

Last updated July 25, 2019

Approved by: Krish Tangella MD, MBA, FCAP

The Homocysteine Blood Test measures homocysteine levels in blood. It is used to detect vitamin B deficiency or genetic disorders affecting homocysteine metabolism.


What are the other Names for this Test? (Equivalent Terms)

  • Homocysteine Cardiac Risk Blood Test
  • Plasma Total Homocysteine Blood Test 

What is Homocysteine Blood Test? (Background Information)

  • Homocysteine is an amino acid found in most cells of the body, in trace amounts. It is an intermediate in the conversion of the amino acid methionine into other products, such as cysteine
  • The metabolism of methionine through homocysteine involves enzymes that use vitamins B6 (pyridoxine), B9 (folate), and B12 (cobalamin). Ample supplies of these B vitamins keep the enzymes functioning and prevent homocysteine buildup
  • Normally, homocysteine levels are low, because it is constantly turned into other products. In the case of vitamin B deficiencies or genetic enzyme defects, the metabolism of methionine through homocysteine may slow or stop. This results in elevated homocysteine levels and it accumulates in the body cells
  • This may increase the risk of cardiovascular disease, because large amounts of homocysteine can damage the inner endothelial lining of blood vessels, change clotting factor levels, and make platelets more prone to aggregation
  • The Homocysteine Blood Test measures homocysteine levels in blood. It is used to detect vitamin B deficiency or genetic disorders affecting homocysteine metabolism. This also provides an indirect assessment of the risk for cardiovascular diseases 

What are the Clinical Indications for performing the Homocysteine Blood Test?

Following are the clinical indications for performing a Homocysteine Blood Test:

  • Fatigue
  • Pale appearance
  • Rapid heart rate
  • Trouble breathing
  • Chest pain radiating to the jaw
  • Tingling in the extremities
  • Glaucoma
  • Nearsightedness
  • Dizziness
  • Seizures 

How is the Specimen Collected for Homocysteine Blood Test?

Following is the specimen collection process for Homocysteine Blood Test:

Sample required: Blood

Process: Insertion of a needle into an arm vein.

Preparation required: Fasting for 2-12 hours may be necessary 

What is the Significance of the Homocysteine Blood Test Result?

The significance of the Homocysteine Blood Test is explained:

  • Increased homocysteine blood levels may indicate:
    • Vitamin B deficiency
    • Chronic kidney failure
    • Homocystinuria (a genetic disorder)
    • Coronary artery disease (CAD) 

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario. 

Additional and Relevant Useful Information:

  • In pregnant women, elevated blood homocysteine levels may affect fetal development, especially of the nervous system
  • Homocysteine levels lag behind vitamin B12 levels; so treatment for possible vitamin B12 deficiency may be started, even before the results of this test becomes available
  • With rare exceptions, vitamin B12 is available only from animal sources. Individuals with vegan diets are at an increased risk for vitamin B12 deficiency, and must supplement their diets with foods containing vitamin B12 

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Sept. 2, 2014
Last updated: July 25, 2019