Vitamins
Methylmalonic acidMMA
Specific marker of intracellular B12 deficiency; rises before serum B12 falls.
Sample
Serum or urine
Clinical reference range
0.07 to 0.27 µmol/L
Adult
Conv: 0.07–0.27 µmol/L
Biology
What it measures
Methylmalonyl-CoA mutase requires adenosylcobalamin; deficiency causes accumulation of MMA.
Clinical use
Why we order it
Confirm functional B12 deficiency when serum B12 is borderline.
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