Methylmalonic Acid Test

What is a methylmalonic acid test?

A methylmalonic (meth-uhl-muh-LAHN-ick) acid test is a way to test for vitamin B12 deficiency. Your provider uses a sample of your blood or urine (pee) to look for high levels of methylmalonic acid (MMA). When you have low levels of B12 (also called cobalamin) or you aren’t absorbing B12 properly, your body makes more MMA.

Why would I need an MMA test?

Your provider might order a methylmalonic acid blood test:

• If you have symptoms of B12 deficiency, like feeling tired or weak, digestive issues (like diarrhea or abdominal pain), numbness or tingling in your hands or feet, or lack of appetite.
• At birth, to screen for methylmalonic acidemia (also called methylmalonic aciduria), a rare genetic disorder.

Providers most often use an MMA urine test to monitor methylmalonic acidemia.

It’s important to accurately diagnose B12 deficiency because it can be a sign of health conditions that can lead to nerve damage, like pernicious anemia and diabetes-related neuropathy.

Why would a provider test MMA instead of B12?

While it might seem more obvious to check B12 levels directly to see if they’re low, there are benefits to testing both B12 and MMA levels. Testing methylmalonic acid levels gives your provider more information and potentially a more accurate diagnosis.

For instance, tests could show that you have normal levels of B12 but your body’s not able to use it (you might hear this called “bioavailability”). Since low levels of B12 cause your body to make MMA, your MMA levels can give your provider information about whether or not your body’s using B12, even if it seems like you have enough. High MMA levels may also allow providers to detect and treat potential health conditions earlier.

How does a methylmalonic acid test work?

For a methylmalonic acid test, your provider will order a blood draw or a urine test to get a sample. A blood draw is done at a lab, hospital or doctor’s office. You might collect pee at home and bring it into the lab or provide a pee sample at a doctor’s office. A pathology lab (where they examine body fluids and tissues) will measure the MMA levels in your blood or pee.

Your provider may also request a homocysteine test and use both its results and the MMA test results to make a diagnosis.

How do I prepare for a methylmalonic acid test?

You’ll need to prepare differently depending on which test your provider will use for a methylmalonic acid test. Ask your provider if there are any special instructions. In general, you may have to fast (not eat) for several hours before the test. You may need to avoid eating certain foods or taking certain medications before a 24-hour urine test.

What happens during a methylmalonic acid test?

What to expect during a methylmalonic acid test depends on what kind of sample you need for the test:

• For a blood test, you’ll sit in a chair with one arm extended. A phlebotomist will use a needle to take blood from your arm, near your elbow. When they’re done, they’ll remove the needle from your arm and have you apply pressure to the area with gauze. They’ll put a bandage over it.
• For a 24-hour urine test, you’ll collect your pee in a sterilized container over a 24-hour period. A provider will give you instructions on how to do the collection. When you’re done, you’ll take the container to a lab for analysis.
• For a urinalysis — or a single sample of pee — you’ll collect your pee in a small, sterile container at home or a provider’s office. Your provider will give you directions on how to pee into the container.
• For a newborn screen, a healthcare provider will use a needle to take a small amount of blood from your baby’s heel. This is usually done in the hospital within a day or two after birth.

What happens after a methylmalonic acid test?

There are no special instructions you have to follow once you’ve completed a blood or urine test. A lab will analyze the sample and send the results to your provider. They also might show up in your electronic medical records.

What are the risks of a methylmalonic acid test?

There’s a small risk of infection with any blood test. Risks of urine tests include not collecting correctly (especially in a 24-hour urine test) and contamination in the sample — like bacteria from poop — that could make the results inaccurate.

What’s a normal MMA level?

Normal blood and urine MMA levels can vary by lab. Normal blood (serum) MMA levels are usually under 0.40 µmol/L (micromole per liter, also written, umol/L or mcmol/L). Urine MMA levels as high as 4.0 mmol/mol crt (millimole per mole of creatinine) can be normal. Be sure to check the reference range provided on your results.

How long does it take to get the results of a methylmalonic acid test?

It can take anywhere from a day to a week or two to get the results of a methylmalonic acid test. Ask your provider when to expect results.

What happens if I have high levels of MMA?

If you have high levels of MMA, you may need additional testing or treatment for B12 deficiency. Your provider will likely look at your MMA results along with the results of other tests, including B12 and homocysteine tests.

If your newborn has high MMA levels, they may have methylmalonic acidemia. Your provider will probably order additional testing to confirm a diagnosis. Treatments for methylmalonic acidemia include supplements, eating low-protein foods and avoiding certain amino acids in foods.

What do normal B12 levels and elevated MMA mean?

If you have normal B12 levels and elevated MMA, you might still have a B12 deficiency — especially if you have symptoms. It might be an early or mild B12 deficiency. This doesn’t necessarily mean that it’ll get worse. Your provider can help determine whether you need treatment.

When should I call my doctor?

See a healthcare provider if you have symptoms of B12 deficiency or have any questions about your test results.

A note from Cleveland Clinic

Sometimes, healthcare providers can test one part of your body to learn more about how another part is working. This is how a methylmalonic acid test works — high levels of MMA let your provider know that you might not have the right level of B12 or that your body’s not absorbing enough of it. This can be important information in diagnosing conditions that can damage your nerves — and treating them as early as possible. Talk to your provider if you have any concerns about an MMA test or its results.