Homocysteine levels: what's normal, high and low
An amino acid that can damage blood vessels at high levels. Tied to B vitamin status (B12, folate, B6).
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
The short answer
Homocysteine is measured with a standard blood draw after an 8–12 hour fast. A typical reference range is 4.00 – 10.0 umol/L. At TestWell it's $27.99 all-in as Homocysteine, results in 2–5 business days, drawn at Quest or Labcorp. An out-of-range result is a prompt to look closer, not a diagnosis.
- Units
- umol/L / µmol/L
- Sample
- Blood draw
- Fasting
- 8–12 hours
- Results
- 2–5 business days
- Price
- $27.99
- Labs
- Quest or Labcorp · BioReference in NY/NJ
Homocysteine Reference Range
These are the typical adult reference ranges used by major US labs. Your report will include the specific range used by the lab that processed your sample.
| Population | Range |
|---|---|
| age 18+ | 4.00 – 10.0 umol/L |
Reference ranges are educational. Always interpret your result with the specific range printed on your lab report and discuss anything outside the range with a clinician.
Have a result in hand? analyze it with your AI assistant using these reviewed ranges, or run it through our explainer. Tools: look up another marker's range · convert lab units
What your Homocysteine result may mean
Often reflects B12, folate, or B6 deficiency, kidney disease, or genetic factors. May increase cardiovascular risk.
What a high Homocysteine means: causes, symptoms, next steps ↓Educational only — not a diagnosis. Many factors can influence a single result. Discuss anything that concerns you with a healthcare provider.
What does a high Homocysteine mean?
High homocysteine most often reflects low folate, B12 or B6, kidney disease, hypothyroidism, smoking, heavy coffee or alcohol intake, or medications (methotrexate, metformin, some anticonvulsants); MTHFR gene variants contribute modestly. It is associated with cardiovascular and clot risk and, at very high levels, with neurological effects, though lowering it with vitamins has not clearly reduced heart attacks. Checking and correcting the B vitamins is the practical step.
Common causes of a high Homocysteine
- Folate, vitamin B12 or B6 deficiency
- Chronic kidney disease
- Hypothyroidism
- MTHFR variants (mild effect), rare homocystinuria (very high)
- Medications: methotrexate, metformin, phenytoin, carbamazepine, nitrous oxide exposure
- Smoking, heavy alcohol or coffee, sedentary lifestyle
Ordered from most to least common.
Symptoms that can go with it
- None from homocysteine itself
What clinicians usually check next
- Folate, vitamin B12 (with methylmalonic acid) and B6
- Kidney function and TSH
- Repeat 8–12 weeks after correcting deficiencies
Follow-up tests at TestWell: TSH (Thyroid Stimulating Hormone) ($26.99), TSH + Free T4 ($27.99), Vitamin B12 ($25.99), Methylmalonic Acid (MMA) ($49.99), Folate (Vitamin B9) ($32.99).
Should I take methylfolate for high homocysteine?
First find out whether folate, B12 or B6 is actually low, and whether kidney or thyroid function explains it. Replacing a documented deficiency lowers homocysteine; broad supplementation without a deficiency hasn't shown cardiovascular benefit.
Educational only — not a diagnosis. A single result outside the range is a prompt to look closer with a clinician.
How do you get a Homocysteine test?
Order online, a licensed physician reviews the requisition, and you walk into a nearby lab for the draw. Homocysteine is available on its own or inside these panels — panels cost less per marker when you want the fuller picture.
| Option | Includes | Price |
|---|---|---|
| Homocysteine | This marker only | $27.99 |
| Comprehensive B12 Deficiency Panel | 3 tests | $79.99 |
| Inflammation Panel | 7 tests | $119.99 |
| Longevity & Anti-Aging Panel | 13 tests | $239.99 |
| Healthy Aging Panel | 15 tests | $299.99 |
Quest vs. Labcorp for Homocysteine: which lab should you pick?
Both are CLIA-certified national labs and the result is clinically equivalent, so pick whichever location is closer. Your report will print that lab's own reference range, which can differ slightly from the table above.
| Lab | Available | Price |
|---|---|---|
| Quest Diagnostics | Yes | $27.99 |
| Labcorp | Yes | $28.99 |
| BioReference (NY & NJ) | Yes | $32.99 |
Need help choosing a location? Use the lab finder to see draw sites near your ZIP.
Related Heart Health biomarkers
Markers commonly tested alongside Homocysteine.
Frequently asked
What does a high Homocysteine mean?
High homocysteine most often reflects low folate, B12 or B6, kidney disease, hypothyroidism, smoking, heavy coffee or alcohol intake, or medications (methotrexate, metformin, some anticonvulsants); MTHFR gene variants contribute modestly. It is associated with cardiovascular and clot risk and, at very high levels, with neurological effects, though lowering it with vitamins has not clearly reduced heart attacks. Checking and correcting the B vitamins is the practical step.
Should I take methylfolate for high homocysteine?
First find out whether folate, B12 or B6 is actually low, and whether kidney or thyroid function explains it. Replacing a documented deficiency lowers homocysteine; broad supplementation without a deficiency hasn't shown cardiovascular benefit.
Do I need a doctor's order to test my homocysteine?
No. TestWell's licensed physician network reviews and approves your order — usually within minutes. You can place an order online without an in-person visit or a referral from your own doctor.
How long does it take to get Homocysteine results?
Most Homocysteine results are available in 1–3 business days after your specimen arrives at the lab. You'll get an email the moment your results are ready, with everything viewable in your TestWell portal.
How much does a Homocysteine test cost?
Our Homocysteine starts at $27.99. That's the all-in price — no copays, no insurance hoops, no surprise bills. HSA and FSA cards are accepted.
Do I need to fast before my Homocysteine test?
Yes — for the most accurate result, fast for 8–12 hours before your blood draw. Water is fine; coffee, food, and supplements are not. Your prep instructions will be included with your order.
Which lab will process my Homocysteine test?
Your test will be processed by Quest Diagnostics, Labcorp, or BioReference depending on which is closest to you and which lab carries the test. All three are CLIA-certified and trusted by hospitals nationwide. You'll choose your lab during checkout from 4,000+ locations.
Ready to test your homocysteine?
Order in two minutes, get physician-approved, and visit a lab the same day. Starts at $27.99.