Methylmalonic Acid, Serum

Methylmalonic Acid, Serum

What it is

The Methylmalonic Acid (MMA), Serum test measures the level of methylmalonic acid in the blood. MMA is a substance produced when the body breaks down certain amino acids and fatty acids. Elevated serum MMA levels are often an early and sensitive marker of vitamin B12 (cobalamin) deficiency, as B12 is required for the metabolism of MMA. This test is more specific than a serum vitamin B12 level alone in detecting early or subclinical deficiency.

Uses

This test is primarily used to diagnose or confirm vitamin B12 deficiency, especially in patients with borderline or inconclusive B12 test results. It is also used to investigate unexplained anemia, neuropathy, or cognitive decline. In rare cases, it helps detect inherited metabolic disorders such as methylmalonic acidemia.

Symptoms That May Lead to the Test

Doctors may order this test if you experience symptoms such as persistent fatigue, weakness, tingling or numbness in hands and feet, difficulty walking, memory loss, mood changes, or unexplained anemia. It may also be recommended for older adults, vegans, or individuals with gastrointestinal conditions that affect B12 absorption (such as Crohn’s disease, celiac disease, or pernicious anemia).

Abnormal Results

High Serum MMA: Strongly suggests vitamin B12 deficiency, even when serum B12 levels appear normal. It can also be elevated in patients with kidney dysfunction or rare inherited metabolic disorders.

Normal Serum MMA: Indicates adequate B12 status and no significant impairment in the metabolic pathway dependent on vitamin B12.

Risks

The test requires a standard blood draw, with minimal risks such as slight pain, bruising, or dizziness at the puncture site. These effects are temporary and usually resolve quickly.