06/05/2026
Your serum B12 can look completely normal — and you can still be functionally deficient. 🧬
Here's what most doctors don't test (and why it matters):
🔬 Serum B12 only tells you what's circulating in your blood — not what's getting INTO your cells.
The two markers that actually reveal functional B12 status:
→ Homocysteine — rises when B12, B6, and folate are insufficient. Also a key cardiovascular risk marker.
→ MMA (Methylmalonic Acid) — the gold standard. Shows whether B12 is working at the cellular level, even when serum B12 looks "fine."
When both MMA and homocysteine are elevated = confirmed functional B12 deficiency.
Ask your doctor to run the full panel if you:
✔ Have unexplained fatigue, brain fog, or mood changes
✔ Take metformin, PPIs, or oral contraceptives
✔ Eat plant-based
✔ Have gut issues (IBS, SIBO, Celiac, IBD)
✔ Are over 50
Save this for your next appointment. 📌