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Methylmalonic Acid (Urine)

Does this test have other names?

Urinary methylmalonic acid (MMA), urinary MMA

What is this test?

This test measures the amount of a substance called methylmalonic acid (MMA) in your urine.

MMA is typically made in tiny amounts when you digest protein. Your body makes large amounts of MMA if you have a drop in the amount of vitamin B12. MMA is excreted in your urine.

Your body needs B12 to make red blood cells and to help your central nervous system function properly. Low levels of B12 can cause anemia, when your body does not make enough red blood cells.

This test is used to diagnose a mild and early shortage of vitamin B12. A high level of MMA can mean that that you have a low level of B12. Vitamin B12 deficiency is the most common cause of MMA production.

Foods that can increase B12 levels include red meats, shellfish, fish, dairy, and cereals fortified with the vitamin. If you are a strict vegetarian, you may be at higher risk for a B12 deficiency. If you are pregnant and are a vegetarian, you may want to take a B12 supplement. This is especially important if you plan to exclusively breastfeed your baby. Otherwise, your child may also be especially susceptible to a B12 deficiency.

Why do I need this test?

You may have this test if your doctor suspects that you have a vitamin B12 deficiency. You may also have this test if you have symptoms of neuropathy, or loss of movement. This can include numbness and tingling in your hands and feet.

Other symptoms of B12 deficiency include:

  • Difficulty walking

  • Mood swings

  • Numbness in your hands or feet

  • Difficulty in thinking clearly

  • Fatigue

  • Headaches

You may also have this test if your doctor suspects that you have methylmalonic academia, an uncommon metabolic disorder in which the body can't process certain fats and proteins. The disease is usually diagnosed in infants and can be mild or life-threatening.

What other tests might I have along with this test?

Your doctor may also order a urine creatinine test. Creatinine is a waste product stored in the muscles and excreted by your kidneys. The urine MMA-creatinine ratio is an accurate way of testing for B12 deficiency.

Your doctor might also order these tests:

  • Folic acid test. You may have this blood test because the symptoms of a folic acid deficiency are similar to the symptoms of a B12 deficiency.

  • Schilling test to help find out the cause of a vitamin B12 deficiency.

  • Complete blood cell count, or CBC, to identify megaloblastic anemia, a disorder of abnormally large red blood cells. A vitamin B12 deficiency can be one cause of megaloblastic anemia. 

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Results are given in micrograms per milligram (mcg/mg). The normal range for a MMA-to-creatinine ratio in a urine sample is less than 3.8 mcg/mg per mg of creatinine.

If you have higher levels of MMA, you may have early or mild B12 deficiency.

Higher levels may also mean you have kidney disease. Infants with higher levels of MMA may have methylmalonic acidemia.

How is this test done?

This test requires either a random or 24-hour urine sample. For a 24-hour urine sample, you must collect all the urine you produce for 24 hours. Empty your bladder completely first thing in the morning without collecting it and note the time. Then collect your urine every time you go to the bathroom for the next 24 hours.

Does this test pose any risks?

This test poses no known risks.

What might affect my test results?

Other factors aren't likely to affect your results.

How do I get ready for this test?

Don't drink alcohol before the test.