Homocysteine blood test
In short
A typical adult homocysteine result is under 15 µmol/L. A mild rise is common and often comes from low B vitamins or reduced kidney function. It is one clue to heart and blood vessel risk, not a diagnosis. Always read your result against the range printed on your own report.
A protein building block that rises when B vitamins run low.
Homocysteine is made when the body breaks down protein. Vitamins B12, B6 and folate help clear it, so a high level can point to low levels of these. Doctors also use it as one of many clues to heart and blood vessel risk.
Is my Homocysteine high or low?
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Typical range
| For | Range | Unit |
|---|---|---|
| Adults | under 15 | µmol/L |
Typical ranges for adults. Labs differ a little, so the range printed next to your result is the one to go by.
If your Homocysteine is high
A mild rise is common and often comes from low B vitamins or reduced kidney function. It is one clue to heart and blood vessel risk, not a diagnosis.
Common reasons
- Low vitamin B12, folate or vitamin B6
- Reduced kidney function
- Older age, smoking or heavy drinking
- An underactive thyroid
- Some medicines that affect how the body uses B vitamins
- A common inherited gene variant that slows how the body uses folate
- Less often: a rare inherited condition that causes very high levels
What can throw it off
A meal shortly before the test, or a sample left too long before it is spun, can push the result up.
Questions to take to your appointment
- 1Could low B vitamins explain this?
- 2Should my B12 and folate be checked?
- 3Could my kidneys or medicines be raising it?
Read together with
Doctors rarely read Homocysteine alone. These usually sit next to it.
- Vitamin B12A vitamin needed for healthy nerves and red blood cells.
- FolateA B vitamin the body needs to make red blood cells.
- CreatinineA waste product from muscles that the kidneys clear.
- eGFRAn estimate of how much blood your kidneys filter each minute.
- TSHA brain hormone that tells the thyroid how hard to work.
Quick answers
What is the homocysteine blood test?
Homocysteine: A protein building block that rises when B vitamins run low. Homocysteine is made when the body breaks down protein. Vitamins B12, B6 and folate help clear it, so a high level can point to low levels of these. Doctors also use it as one of many clues to heart and blood vessel risk.
What is a normal homocysteine level?
For most adults, homocysteine is typically under 15 µmol/L. Labs differ a little, so the range printed next to your result is the one to go by.
What does a high homocysteine mean?
A mild rise is common and often comes from low B vitamins or reduced kidney function. It is one clue to heart and blood vessel risk, not a diagnosis. Common reasons include low vitamin B12, folate or vitamin B6; reduced kidney function; older age, smoking or heavy drinking; and an underactive thyroid. A doctor reads it together with your other results and how you feel.
What can affect my homocysteine result?
A meal shortly before the test, or a sample left too long before it is spun, can push the result up.
What should I ask my doctor about my homocysteine?
Questions worth taking to the appointment: Could low B vitamins explain this? Should my B12 and folate be checked? Could my kidneys or medicines be raising it?
What this page can’t do
It reads each number on its own.
Doctors read results together — ALT with AST, ferritin with hemoglobin, TSH with free T4. A pattern says more than any single flag.
It doesn't know you.
Your age, your medicines, how you feel and your last result all change what a number means.
It doesn't remember.
Close this page and your results are gone. That's on purpose: nothing was ever sent to us.
We also make Vita: Health Coach, an app for those parts. It reads your whole report with your medicines and history in mind, answers follow-up questions in plain words, and keeps your reports in one place — for you and for the people you look after.
Vita: Health Coach on the App StoreSources
- ABIM — Laboratory Test Reference Ranges (January 2026)
- MedlinePlus — Homocysteine test
- Mayo Clinic Laboratories — Homocysteine, Total, Serum
Stuck on a word? See the medical words. How we choose our sources. More about Vita Health Coach.