Methylmalonic acid (MMA) is a byproduct of amino acid metabolism.

Normally, MMA is converted with the help of vitamin B12.

When vitamin B12 is deficient, MMA accumulates in blood and urine.

Clinical uses include:

Detecting vitamin B12 deficiency (more sensitive than serum B12 alone).

Supporting diagnosis of methylmalonic acidemia, a rare inherited metabolic disorder.

Differentiating between folate deficiency and vitamin B12 deficiency.

The qualitative test reports presence or absence of elevated MMA rather than exact concentration.

Analyte: Methylmalonic acid in blood or urine.

Normal Result: Negative (no abnormal MMA detected).

Positive Result: Indicates elevated MMA → suggests vitamin B12 deficiency or metabolic disorder.

Clinical Use:

Confirms functional vitamin B12 deficiency.

Helps distinguish between nutritional vs inherited causes of elevated MMA.

Guides treatment decisions in suspected metabolic or hematologic disorders.