Methylmalonic acid (MMA)
Metabolic byproduct that can rise in the blood with vitamin B12 deficiency
Also known as
Definition
Methylmalonic acid (MMA) is made in small amounts when the body breaks down protein. Vitamin B12 is needed to break it down further; if B12 is lacking, MMA can build up. It is measured in blood or urine, mainly together with other tests when vitamin B12 deficiency is suspected. It is also part of newborn screening for the rare inherited disorder methylmalonic acidemia.
| Parameter | Value |
|---|---|
| Unit | µmol/l (nmol/l) |
| Reference Range | Typical for adults in blood: 0.07–0.27 µmol/l (70–270 nmol/l). Labs differ, partly because they use different methods and sample types; the reference range on your own report is what counts. Your doctor interprets the result. |
Agree on your personal target range with your doctor.
Conversion: 1 µmol/l = 1,000 nmol/l. 0.07–0.27 µmol/l therefore equals 70–270 nmol/l.
↓ What a low value means
Low MMA levels are uncommon and are not considered a health problem. If you have questions about your result, discuss it with your doctor.
↑ What a high value means
A raised level can be linked to vitamin B12 deficiency. The test does not show how severe a deficiency is, however. Other values are often used for interpretation, such as homocysteine and vitamin B12 in the blood. In newborns, moderately or highly raised levels can be linked to the rare inherited disorder methylmalonic acidemia, which the child's doctor investigates. Discuss any deviation with your doctor.
When to test
With signs that can fit vitamin B12 deficiency, such as fatigue, dizziness, shortness of breath, tingling in the hands or feet, mood changes, confusion or pale skin. The risk of deficiency is higher, among others, with a strict vegetarian or vegan diet, with celiac disease or Crohn's disease, after certain stomach or bowel surgeries and from age 75. Sometimes you may be asked to fast.
Frequently asked questions
How are methylmalonic acid and vitamin B12 connected? +
Vitamin B12 is needed to break MMA down further. If it is lacking, more MMA is made than is broken down, and the level can rise. The body cannot make vitamin B12 itself; it comes from foods such as fish and seafood, dairy products, eggs, meat and poultry, and from fortified foods.
Is MMA measured in blood or urine? +
Both are possible. For the blood test, blood is drawn from a vein in your arm. In urine, MMA is measured either in a 24-hour collection or in a single sample taken at any time of day. Newborn screening needs only a few drops of blood from the heel.
Does a raised level show how severe a vitamin B12 deficiency is? +
No. A raised MMA level can point to a deficiency but says nothing about its extent. Your doctor therefore compares it with other values such as homocysteine and vitamin B12 and takes symptoms and medical history into account.
Why is MMA measured in newborn screening? +
It helps detect methylmalonic acidemia, a rare inherited metabolic disorder. Its signs range from mild to severe, such as vomiting, dehydration or developmental delays. Left untreated, it can have life-threatening consequences.
Methylmalonic acid (MMA)
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.