A methylmalonic acid (MMA) test measures the amount of methylmalonic acid in blood or urine to detect vitamin B12 deficiency and certain metabolic disorders. Elevated MMA indicates impaired B12-dependent metabolism at the cellular level, even if serum B12 looks normal. It’s used when neurological signs or borderline B12 levels occur, or to screen for inherited methylmalonic acidemia; results must be interpreted with clinical and renal function data.

Serum B12 is the usual first test, but methylmalonic acid (MMA) is more sensitive for detecting true tissue B12 deficiency. If serum B12 is low‑normal or you have neurological signs, measure MMA to confirm deficiency. Remember MMA can be elevated with renal impairment, so interpret alongside kidney function and the clinical picture. Start with serum B12 and add MMA when results or symptoms are ambiguous.

Normal fasting serum methylmalonic acid (MMA) is typically about 70–271 nmol/L (0.07–0.27 µmol/L). Some laboratories use slightly different cutoffs; values above roughly 0.4–0.56 µmol/L are commonly considered elevated and may indicate vitamin B12 deficiency. Urine MMA reference ranges differ. Always compare results with the laboratory’s reference interval and discuss abnormal findings with your clinician.

Methylmalonic acid (MMA) is normally low—laboratory cutoffs vary but about 0.4 μmol/L (400 nmol/L) is commonly used. In vitamin B12 deficiency MMA typically rises above that level, often into the 0.4–2.0 μmol/L range; severe or prolonged deficiency can produce levels of several μmol/L. Degree of elevation correlates with deficiency severity and clinical context.

Methylmalonic acidemia (MMA) symptoms often appear in infancy: poor feeding, vomiting, dehydration, lethargy, low muscle tone, failure to thrive, developmental delay, seizures and breathing difficulties. Metabolic signs include severe metabolic acidosis and high ammonia. Later-onset forms can cause growth delay, recurrent vomiting, movement disorders, progressive neurological decline, kidney dysfunction and psychiatric symptoms. Episodes may lead to coma if untreated.

An MMA (methylmalonic acid) blood test is a moderately priced specialized test — generally more expensive than a routine B12 check but not prohibitively costly. Prices vary by country and lab; out-of-pocket costs often range roughly $50–200 in the US and a few hundred to a few thousand rupees in India. Many public systems and insurers cover it when medically indicated.