About Methylmalonic Acid
Methylmalonic acid (MMA) is a metabolic byproduct that accumulates in the blood and urine specifically when vitamin B12 is functionally deficient at the cellular level. MMA is a far more sensitive indicator of B12 deficiency than serum B12 itself — many people have a 'normal' B12 level yet elevated MMA, revealing tissue-level deficiency that causes neurological damage before anemia appears. It is particularly valuable in older adults and people taking metformin or acid-suppressing medications, where B12 deficiency is common but often missed on standard panels.