What is Methylmalonic Acid (MMA)?
MMA often increases when vitamin B12 availability at the cellular level is insufficient. It can therefore add clarity when B12 levels are borderline or do not match the broader picture. It is typically assessed together with B12 and folate.
Why is Methylmalonic Acid (MMA) relevant?
MMA is a functional marker for vitamin B12 at the cellular level: when B12 is insufficiently available inside cells, MMA rises because a specific enzymatic step is disrupted. That makes MMA particularly valuable at borderline B12 values: the blood reading can look 'normal' while a functional deficiency is still present. For people with unexplained fatigue, tingling, or cognitive complaints, MMA can offer clarity that B12 alone does not.
How to read Methylmalonic Acid (MMA) in context
MMA is almost always interpreted together with vitamin B12 and optionally homocysteine — only in combination can you tell whether an actual cellular deficiency is present. Kidney function affects MMA, so with reduced kidney function the marker is read differently. After supplementation, re-testing is only meaningful after several weeks; the system needs time for cellular status to recover.