Metabolic
Methylmalonic Acid
LOINC 13964-2 · nmol/L
What it is
Methylmalonic acid (MMA) is a substance that builds up when vitamin B12 is in short supply, making it a sensitive marker of B12 status.
Why it matters
Because MMA rises early when B12 is low, it can confirm a B12 deficiency even when B12 itself looks borderline.
What high values can mean
A higher value suggests your cells are short of usable vitamin B12.
What low values can mean
A lower or normal value suggests adequate B12 at the cellular level.
How to improve it
When B12 is the cause, correcting it through diet or supplements (as advised) brings MMA down.
Food & lifestyle
Meat, fish, eggs and dairy supply B12; people on plant-based diets may need fortified foods or supplements.
Preparing for the test
A blood (or urine) test; fasting is not usually required — follow your lab's instructions.
When to talk to a doctor
Discuss a high MMA with a doctor, especially with tiredness, tingling or balance problems.
Related markers
Sources
- MedlinePlus (NIH)
- NIH Office of Dietary Supplements
Content reviewed on June 26, 2026
Medical disclaimer
This content is for educational purposes only. It is not medical advice and does not diagnose, treat, or prevent any condition. Reference ranges vary between laboratories — always use the range printed on your report and discuss your results with a healthcare professional.
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