Methylmalonic Acid (MMA)
Organic acid that accumulates when methylmalonyl-CoA mutase activity is impaired by vitamin B12 deficiency; elevated serum or urine MMA is a sensitive functional marker of B12 deficiency.
Also: MMA
MMA elevation distinguishes B12 from folate deficiency (folate deficiency raises homocysteine but not MMA). Renal impairment also raises MMA, so interpretation must account for eGFR. The 12th edition treats MMA alongside total homocysteine as the preferred functional B12 status panel because serum B12 alone has poor sensitivity in subclinical deficiency.
How one textbook covers it
Modern Nutrition in Health and Disease, 12th ed. — Ch 28: Cobalamin (Vitamin B12)
MMA elevation distinguishes B12 from folate deficiency (folate deficiency raises homocysteine but not MMA). Renal impairment also raises MMA, so interpretation must account for eGFR. The 12th edition treats MMA alongside total homocysteine as the preferred functional B12 status panel because serum B12 alone has poor sensitivity in subclinical deficiency.
Related terms
Cobalamin, Folate, Homocysteine