Understanding MMA & Homocysteine
These two blood tests confirm a true vitamin B12 deficiency at the cellular level. They are especially useful when a standard B12 level is borderline or the picture is unclear.
What They Measure
When B12 is truly lacking, certain substances build up in the blood because B12 is needed to process them. Measuring those substances reveals a deficiency that a standard B12 level can miss.
| Component | What It Means |
|---|---|
| Methylmalonic AcidMMA | Rises when B12 is deficient at the cellular level. A high MMA is a sensitive and specific sign of true B12 deficiency. |
| Homocysteine | Rises with B12 or folate deficiency. It supports the picture and is also a marker studied in cardiovascular health. |
What’s Most Important to Know
These tests are typically ordered as a follow-up when a standard B12 result is borderline but symptoms suggest deficiency.
A high MMA (with or without high homocysteine) helps confirm that treatment is truly needed. Dr. Mui will interpret these together with your B12 level and symptoms.
This page is for general education and does not replace a conversation with your doctor about your specific results. Want to review your results? Book a visit and we’ll go through them together.