Methylmalonic Acid (MMA) Test

What is a methylmalonic acid (MMA) test?

This test measures the amount of methylmalonic acid (MMA) in your blood or urine. MMA is a substance made in small amounts during metabolism. Metabolism is the process of how your body changes food into energy. Vitamin B12 plays an important role in metabolism. If your body doesn't have enough vitamin B12, it will make extra amounts of MMA. High MMA levels can be a sign of a vitamin B12 deficiency. Vitamin B12 deficiency can lead to serious health problems including anemia, a condition in which your blood has a lower than normal amount of red blood cells.

Other names: MMA

What is it used for?

An MMA test is most often used to diagnose a vitamin B12 deficiency.

This test is also used to diagnose methylmalonic acidemia, a rare genetic disorder. Symptoms of this disorder can range from mild to severe and may include vomiting, dehydration, developmental delays, and intellectual disability. The test is usually included as part of a series of tests called a newborn screening. A newborn screening helps diagnose a variety of serious health conditions.

Why do I need an MMA test?

You may need this test if you have symptoms of a vitamin B12 deficiency. These include:

• Fatigue
• Loss of appetite
• Tingling in hands and/or feet
• Mood changes
• Confusion
• Irritability
• Pale skin

If you have a new baby, he or she will probably be tested as part of a newborn screening.

What happens during an MMA test?

MMA levels may be checked in blood or urine.

During a blood test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

During a newborn screening, a health care provider will clean your baby's heel with alcohol and poke the heel with a small needle. The provider will collect a few drops of blood and put a bandage on the site.

MMA urine testing may be ordered as a 24-hour urine sample test or a random urine test.

For a 24-hour urine sample test, you'll need to collect all urine passed in a 24-hour period. Your health care provider or a laboratory professional will give a container to collect your urine and instructions on how to collect and store your samples. A 24-hour urine sample test generally includes the following steps:

• Empty your bladder in the morning and flush that urine away. Record the time.
• For the next 24 hours, save all your urine passed in the container provided.
• Store your urine container in the refrigerator or a cooler with ice.
• Return the sample container to your health care provider's office or the laboratory as instructed.

For a random urine test, your sample of urine may be collected any time of the day.

Will I need to do anything to prepare for the test?

You may need to fast (not eat or drink) for several hours before your test. Your health care provider will let you know if there are any special instructions to follow.

Are there any risks to the test?

There is very little risk to you or your baby during an MMA blood test. You may experience slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

Your baby may feel a little pinch when the heel is poked, and a small bruise may form at the site. This should go away quickly.

There is no known risk to having a urine test.

What do the results mean?

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 you have or whether your condition is likely to get better or worse. To help make a diagnosis, your results may be compared with other tests including a homocysteine blood test and/or vitamin B tests.

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

If you have questions about your results, talk to your health care provider.

If your baby has moderate or high levels of MMA, it may mean he or she has methylmalonic acidemia. Left untreated, it can cause life-threatening complications. If your baby is diagnosed with this disorder, talk to your child's health care provider about treatment options.

Learn more about laboratory tests, reference ranges, and understanding results.