Homocysteine
Table of contents
Homocysteine is one of the less well-known numbers on my report, but it’s linked to heart and blood vessel health, and to B vitamins. In April 2026 mine was just under the lab’s limit. By October it had dropped well into the comfortable zone, and I think a B12 prescription and better folate had a lot to do with it.
Snapshot
| April 2026 | October 2026 | Lab range | |
|---|---|---|---|
| Homocysteine | 14.36 µmol/L | 9.78 µmol/L | <15.00 |
| Vitamin B12 | 293 pmol/L | 590 pmol/L | 145–569 |
| Folate | 15.1 nmol/L | 30.9 nmol/L | 10.2–73.0 |
| Status | ⚠️ Close to the limit | ✅ Comfortable |
From my October report, with my doctor’s handwritten April value and a tick:
What it is
Homocysteine is an amino acid your body makes while processing methionine, an amino acid found in protein foods. Normally it doesn’t hang around: the body quickly converts it into other useful compounds. That conversion needs three B vitamins:
- Folate (vitamin B9)
- Vitamin B12
- Vitamin B6
If any of these are low, homocysteine builds up in the blood. High homocysteine is linked with damage to the lining of blood vessels and a higher risk of heart disease, stroke and blood clots. It’s also a useful flag that your B-vitamin status might not be great.
What I’m aiming for
The lab’s limit is under 15 µmol/L. My doctor didn’t set a separate target, but I’d like to stay comfortably below the limit rather than just under it. Somewhere around 10 or lower seems a reasonable place for a healthy adult.
Why April was a problem
At 14.36 µmol/L, April was technically normal, but only just. It was one of the “close to the edge” results on my April report.
The B vitamins that clear homocysteine weren’t high either: B12 was 293 and folate 15.1, both in range but towards the lower end. Homocysteine sitting near the top of its range alongside modest B12 and folate suggests the clearing process wasn’t running as well as it could.
On its own, a borderline homocysteine isn’t a big risk. But in April it came alongside higher LDL, higher ApoB and a higher hs-CRP, all heart-related markers leaning the wrong way at once.
Why October is better
Homocysteine dropped to 9.78 µmol/L, and my doctor ticked it. What probably helped:
- Vitamin B12 went up a lot. In early October I was prescribed mecobalamin, a form of B12, as part of the treatment for my neck (B12 supports nerve health). My B12 nearly doubled, from 293 to 590. That’s slightly above the lab’s range, which is almost certainly from the prescription and harmless; see the B12 and folate article.
- Folate doubled too, from 15.1 to 30.9. I didn’t take a folate supplement, so this is probably down to diet. I’m not sure exactly which changes did it.
With more B12 and folate available, the body can clear homocysteine faster, which fits the drop.
What’s next
- Recheck homocysteine at my next full blood test. Once I’ve finished the B12 prescription, B12 will probably fall back, so it’ll be interesting to see whether homocysteine stays down without it.
- If it creeps back towards 15, ask my doctor whether a regular B-vitamin supplement is worth taking.
This is my own personal data, shared for interest only. It’s not medical advice.
Until next time, peace and love!