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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) found 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
13965-9
Short code
Hcys SerPl-sCnc
Synonyms
Hcys SerPl-sCnc
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 This Test Might Be Ordered

Your healthcare provider may recommend this test if you have a family history of heart disease, stroke, or blood vessel problems. It could also be used to monitor conditions like kidney disease, certain genetic disorders, or if you’re taking folic acid or vitamin B supplements.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if your blood is drawn early in the morning. Wear comfortable clothing and plan to stay near the testing site for about 15 minutes.

How the Test Is Performed

A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a slight pinch, but it usually doesn’t cause much discomfort. The blood is then sent to a lab for analysis.

What the Results Mean

Results are typically reported as a concentration value (e.g., micromoles per liter). Higher-than-normal levels may indicate an increased risk of cardiovascular issues or other health concerns, while lower levels might suggest deficiencies in certain vitamins.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Homocysteine

Frequently asked questions

What Does Elevated Homocysteine Mean?
Elevated homocysteine levels can raise the risk of blood clots, heart disease, or stroke. It may also signal underlying conditions like kidney disease or deficiencies in vitamins B6, B9 (folate), or B12, which help metabolize homocysteine. Your provider may recommend lifestyle changes or supplements if needed.
What Does Low Homocysteine Mean?
Low homocysteine levels are less commonly concerning unless they’re part of a broader pattern of vitamin deficiencies. In some cases, they may suggest genetic variations or other metabolic factors, but further evaluation is usually needed to understand the cause.
How Often Should I Get This Test?
Your provider will determine how often to check this test based on your health history, symptoms, and risk factors. Some people may need it yearly, while others may only need it if their levels are already monitored for a specific condition.
  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