Methylmalonic Acid (MMA)

Vitamin B12 plays an important role in metabolism. Part of this role is breaking down MMA into substances that help with metabolism. If your body doesn't have enough vitamin B12, it will continue to make more MMA than is broken down. High MMA levels can be a sign of a vitamin B12 deficiency. Because MMA rises early when B12 is running low, it acts as a sensitive marker of how well your body is actually using B12, even when other tests look borderline.

Vitamin B12 deficiency can happen if you are not eating enough B12 in your diet or if your body has difficulty absorbing it. Your body cannot make vitamin B12 on its own, so you have to get it from the foods you eat.

Vitamin B12 is also found in some fortified foods, meaning the food has vitamins added to it. It's also available as a supplement.

MMA testing is especially useful for adults who have signs of B12 deficiency such as nerve problems in the hands and feet, balance issues, memory trouble, mood changes, or anemia, particularly if they are older or have a digestive condition that makes it harder to absorb nutrients.

If your results show higher-than-normal levels of MMA, it may mean you have a vitamin B12 deficiency. The test can't show how much of a deficiency. To help make a diagnosis, your provider may compare your results with other tests including a homocysteine blood test and/or vitamin B tests.

Mildly high MMA isn't always due to low B12. Reduced kidney function, dehydration, and bacterial overgrowth in the small intestine can also cause modest increases in MMA, so your provider will look at the bigger picture.

Lower-than-normal levels of MMA are not common and are not considered a health problem.

If your baby has moderate or high levels of MMA, it may mean that they have methylmalonic acidemia, an inherited problem in how the body breaks down certain proteins. If it's not treated, it can cause life-threatening complications. If your baby is diagnosed with this disorder, talk to your child's provider about treatment options.

If you have questions about your results, talk to your provider. Your provider will consider your symptoms, medical history, and the results of other blood tests.