Methylmalonic Acid (MMA), Serum

Methylmalonic acid (MMA) is metabolite that can build up when the body does not have enough active vitamin B12 to process certain fats and proteins. Elevated MMA points toward a functional B12 deficiency, even when a standard B12 level looks borderline or does not match associated symptoms. It is often tested alongside vitamin B12 and homocysteine to comprehensively assess B12 status.