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Homocysteine (Total) in Serum or Plasma

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

This test measures the amount of homocysteine, an amino acid that can build up in your blood and may increase your risk of certain health problems.

Quick summary

["Homocysteine levels help assess your risk for heart disease and other vascular conditions."]

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

Key facts at a glance

LOINC
25928-3
Short code
(Hcys)2 24h Ur-sCnc
Synonyms
(Hcys)2 24h Ur-sCnc
Category
chemistry
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have a history of heart disease, stroke, or blood vessel problems, or if you have risk factors like high blood pressure, diabetes, or smoking. It may also be checked if you have symptoms like fatigue, numbness, or memory issues that could be linked to vascular issues.

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 it involves a blood draw. If it’s a urine test, you might need to collect a sample over 24 hours. Always follow your provider’s instructions.

What the Test Involves

For blood tests, a small needle will be used to draw blood from a vein in your arm. For urine tests, you’ll collect a sample in a container at home or during a clinic visit. The sample is then sent to a lab for analysis.

What the Results Mean

Results are typically reported in micromoles per liter (µmol/L). High levels may signal an increased risk for heart disease, nerve damage, or other health concerns. Your provider will interpret results in relation to your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Total Homocysteine

Frequently asked questions

What Are Common Causes of High or Low Results?
High homocysteine levels can be caused by vitamin deficiencies (like folate or B12), certain medications, kidney disease, or genetic factors. Low levels are less common but may occur with certain genetic conditions or overuse of folate supplements.
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. Some people get it every few years if they have known risk factors, while others may need it less often.
Can I Take Anything Before or After the Test?
No, avoid taking supplements like folate or B vitamins (unless approved by your provider) 24 hours before the test, as they can affect results. If you have questions about timing, ask your healthcare team.
  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