What Is a Methylmalonic Acid (MMA) Test?

Methylmalonic acid (MMA) accumulates when vitamin B12 is deficient. It rises earlier than serum B12 drops.

Why MMA Is Useful

• More sensitive than serum B12
• Detects functional deficiency
• Useful when B12 is borderline (200–400 pg/mL)
• Not affected by recent B12 supplementation as quickly

Normal Range

• Below 0.4 µmol/L
• Above 0.4 = B12 deficiency likely

When to Order

• B12 is 200–400 pg/mL with symptoms
• Neuropathy with normal B12
• Before starting lifelong B12 supplementation