What Is a Methylmalonic Acid Test?

Medically Reviewed by Carol DerSarkissian, MD on February 13, 2024
4 min read

Methylmalonic acid (MMA) is a substance that is created when your body digests protein. The amount of vitamin B12 in your body controls how much MMA your body makes. A high amount of MMA typically means you have a vitamin B12 deficiency.

There are two types of low-risk methylmalonic acid tests. One is a blood test. The other is a urine test.

Vitamin B12 is necessary to make red blood cells. It helps your central nervous system work correctly. Vitamin B12 deficiency can lead to anemia. This is a lack of red blood cells. A vitamin B12 deficiency is the most common cause of raised levels of MMA.

A vitamin deficiency slowly develops over months or years. As a deficiency gets worse, so do the symptoms.

Symptoms. Your doctor may call for an MMA test if you begin showing signs of vitamin B12 deficiency. These include:

  • Numbness or tingling in your hands, legs, feet, or other extremities
  • Difficulty walking
  • Swollen or inflamed tongue
  • Confusion or memory loss
  • Weakness
  • Fatigue

Sources of vitamin B. Most people get enough vitamin B12 from the foods they eat. Red meat, shellfish, and dairy are major food sources of vitamin B12. This puts vegetarians and vegans at risk for a vitamin B12 deficiency. Vitamin supplements can be taken to boost your levels of B12.

Methylmalonic acidemia. Your doctor may call for an MMA test if they suspect you have methylmalonic acidemia. This is a genetic disorder in which your body can’t process certain proteins and fats. It typically appears early in life and is tested for during newborn screenings.

Methylmalonic acidemia can be life-threatening if untreated. Symptoms of this disorder can be mild or severe and include:

Pregnancy and kidney disease can lead to abnormal levels of MMA. Treatments using vitamin B12 can help maintain MMA levels during these times.

Preparation. You don’t need to prepare for an MMA blood test. Simply keep your doctor updated on any medications, drugs, and supplements you may be taking. Your doctor may request that you fast before the test.

What to expect. The only pain or discomfort you should feel during an MMA blood test is when your blood is drawn. The needle will cause a slight sting. Your arm may throb but this will soon fade.

Each lab uses slightly different methods and results. Minimal variations from a normal value of MMA may not be a problem. Speak with your doctor for a better understanding of your results.

Risks. Getting blood drawn has little risk. You may experience:

  • Lightheadedness or fainting
  • Multiple punctures to locate the proper vein
  • Hematoma (buildup of blood beneath the skin)
  • Excess bleeding

Other tests. Your doctor may also suggest a homocysteine test to better understand your MMA blood test. Homocysteine is an amino acid that your body uses to make proteins. High levels of homocysteine may indicate low levels of vitamin B.

Another method for testing levels of MMA is through your urine. This version of the MMA test is used to detect mild or early vitamin B12 deficiency.

Preparation. You won’t need much preparation for this test. Don’t drink alcohol before you take it. Keep your doctor updated about any medications, drugs, or supplements you use.

What to expect. Your doctor will request a random sample or a 24-hour sample. A random urine sample requires overnight fasting (except water). You collect your second urination of the day, disposing of the first. For a  24-hour urine sample, you’ll need to collect urine samples over a 24-hour period.

Depending on the results of your MMA blood or urine tests, your doctor order other tests:

  • Urine creatinine tests will look at the waste product that your kidneys put out.
  • A folic acid test will check for a folic acid deficiency. This has symptoms similar to a vitamin B-12 deficiency.
  • A complete blood cell count (CBC) checks for megaloblastic anemia. This is a condition in which your red blood cells are abnormally large. It can be caused by a vitamin B-12 deficiency.

Risks. There aren’t any known risks for these tests.

You may have a vitamin B12 deficiency if you have higher than normal levels of MMA. The tests don’t reveal exactly how serious your deficiency is. You’ll most likely need more tests for that. These tests typically include a vitamin B test and a homocysteine blood test.

It’s possible to have a lower than normal level of MMA. But this isn’t common and is generally isn’t a health issue.