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Homocysteine, Serum or Plasma Concentration

Published: August 9, 2026Updated: August 16, 2026

This test measures the level of homocysteine, a type of amino acid (a building block of proteins) in your blood.

Quick summary

["Homocysteine levels can help assess risks for certain health conditions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
108718-8
Short code
Hcys Msmt SerPl
Synonyms
Hcys Msmt SerPl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Might You Need This Test?

Your healthcare provider may order this test if you have a family history of heart disease, stroke, or blood vessel problems, or if you have symptoms like fatigue, numbness, or memory issues. It may also be checked during routine blood work or if you’re taking certain medications that can affect homocysteine levels.

What Does the Test Involve?

A small sample of your blood is taken from a vein, usually in your arm. The blood is then sent to a lab for analysis. The test looks at how much homocysteine is present in your serum or plasma.

What Are Common Causes of Abnormal Results?

High levels of homocysteine can be linked to genetic factors, certain vitamins (like folate and vitamin B12) being low, kidney disease, or conditions like diabetes. Low levels may occur if you have certain genetic disorders or take specific medications.

What Do My Results Mean?

Results are not always given as a single number, as reference ranges vary by lab and individual health. Your provider will interpret the results in the context of your overall health and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Homocysteine

Frequently asked questions

What Are Possible Side Effects or Risks?
The most common side effect from a blood draw is mild bruising, swelling, or soreness at the injection site. Rarely, there may be a reaction to the needle or infection at the site, but these are uncommon.
How Often Should I Get This Test?
Your provider will determine how often you need this test based on your health status, risk factors, and medical history. It’s not typically a routine screening test unless recommended otherwise.
Can I Prepare for This Test?
You may be asked to fast for 8–12 hours before the test if it’s part of a metabolic panel, but homocysteine testing alone usually doesn’t require fasting. Avoid smoking or drinking alcohol for a few hours before the test if advised by your provider.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy