Vitamin B12 + Methylmalonic Acid (MMA)
Serum B12 alone misses functional deficiency. Pairing it with methylmalonic acid (MMA) catches tissue-level shortfall — critical for vegans, metformin users, and older adults.
Serum B12 alone misses functional deficiency — pairing it with methylmalonic acid (MMA) catches tissue-level shortfall that a normal-looking B12 number can hide. Testing both matters most for vegans, vegetarians, anyone on metformin or a proton-pump inhibitor, and older adults.
The biomarker
- Name: Vitamin B12 + Methylmalonic Acid (MMA)
- Units: B12 pg/mL; MMA nmol/L
- Standard reference range: B12 200–900; MMA < 360
- Optimal range: B12 500–900; MMA < 270
How to read your result
| Result | Interpretation |
|---|---|
| B12 200–400 | Low — add an MMA test |
| B12 400–900 | Adequate |
| B12 < 200 | Deficiency — supplement and investigate |
| MMA > 360 + B12 borderline | Functional deficiency confirmed |
What moves the needle
- Diet. Animal foods or fortified plant foods; vegans must supplement — B12 is not reliably available from unfortified plant sources.
- Testing. Recheck B12 and MMA roughly 3 months after starting a supplement.
- Supplement. Dose varies by source and individual absorption — see your clinician or the product label rather than a fixed rule.
Why this test is worth asking for
- Serum B12 can sit in the "adequate" range while MMA is already elevated — the functional, tissue-level deficiency that B12 alone misses.
- Metformin and proton-pump inhibitors both reduce B12 absorption, so anyone on either long-term is a candidate for periodic testing regardless of diet.
- Vegans and vegetarians have no reliable unfortified dietary source and are the highest-risk group for slow, silent depletion.
Related protocols
Sources
AgeGen lab guides are educational only. We do not provide medical diagnosis, prescribe brands, or recommend specific doses. Talk to a licensed clinician before changing your supplement or medication routine.
