What It Measures
MMA measures the blood level of methylmalonic acid, a byproduct of propionate metabolism that requires vitamin B12 (as adenosylcobalamin) as a cofactor for its conversion to succinyl-CoA. When B12 is insufficient, this conversion stalls and MMA accumulates in the blood and urine.
Methylmalonic acid (MMA) is an organic acid produced during the metabolism of certain proteins and fats. Elevated levels are considered the most sensitive and specific marker for vitamin B12 deficiency at the cellular level, making it critical for detecting functional B12 insufficiency even when serum B12 levels appear normal.
Current Value
What High Means
Elevated MMA strongly suggests functional vitamin B12 deficiency, even if serum B12 is in the low-normal range. It can also indicate methylmalonic acidemia (a rare genetic disorder), kidney dysfunction (reduced clearance), small intestinal bacterial overgrowth (SIBO), or thyroid disease. Persistently high MMA is associated with neurological damage, megaloblastic anemia, cognitive decline, and increased cardiovascular risk.
Possible Symptoms
Fatigue, weakness, numbness and tingling in hands/feet (peripheral neuropathy), difficulty walking, memory problems and cognitive decline, mood changes (depression, irritability), glossitis (swollen tongue), megaloblastic anemia symptoms (pallor, shortness of breath), balance problems.
What Low Means
Low MMA levels are generally normal and indicate adequate vitamin B12 status and proper mitochondrial function. There is no clinical condition associated with abnormally low MMA.
Possible Symptoms
No clinical symptoms are associated with low MMA levels. Low values reflect adequate B12 and normal metabolic function.
Risk Factors
Vitamin B12 deficiency, pernicious anemia, vegan/vegetarian diet without B12 supplementation, malabsorption syndromes (celiac disease, Crohn disease, gastric bypass), chronic kidney disease, SIBO, advanced age (decreased intrinsic factor), long-term metformin or PPI use, methylmalonic acidemia (genetic).
Actionable Advice
Supplements
- •Vitamin B12 (methylcobalamin)
- •Vitamin B12 (adenosylcobalamin)
- •Vitamin B12 (hydroxocobalamin)
- •Folate (methylfolate)
- •Betaine (trimethylglycine)
- •Probiotics
Diet & Lifestyle
- •Ensure adequate dietary B12 from animal products (meat, fish, eggs, dairy) or fortified foods
- •Consider B12 supplementation if vegan, vegetarian, or over age 50
- •Address gut health issues that may impair B12 absorption (SIBO, low stomach acid)
- •Discuss with your doctor if taking metformin or PPIs long-term, as these can deplete B12
- •Request MMA testing if serum B12 is borderline (200-400 pg/mL) to assess true cellular status
- •Limit alcohol intake, which can impair B12 absorption and metabolism
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Related Biomarkers
Resources & Studies
All Readings
| Date | Value | Change |
|---|---|---|
| 2025-08-25 | 72 nmol/L | — |