MMA is the most sensitive and specific marker for B12 deficiency at the tissue level. When B12 is low, MMA accumulates because B12 is required to convert it to succinyl-CoA.
Methylmalonic Acid (MMA) is a metabolite that accumulates when vitamin B12 is deficient at the cellular level. B12 is a required cofactor for the enzyme that converts MMA to succinyl-CoA. When B12 is low—even "low normal"—this conversion slows and MMA builds up in the blood.
MMA testing is considered more sensitive and specific for B12 deficiency than serum B12 levels alone. This is because:
- Serum B12 can appear normal even when cellular B12 is functionally inadequate
- Some people have "subclinical" B12 deficiency with normal B12 but elevated MMA
- MMA elevates before neurological symptoms develop, allowing earlier intervention
MMA is particularly valuable when B12 levels are in the low-normal "gray zone" (200-400 pg/mL) and you need to determine if true deficiency exists. Elevated MMA confirms the body isn't getting enough usable B12.
Price
$37
Results
3-5 days
Lab Network
Quest
Fasting
Not Required
What's Measured
What This Test Measures
This test measures the concentration of methylmalonic acid in your blood, reported in nmol/L or µmol/L. Normal MMA is typically <300 nmol/L (<0.30 µmol/L). Elevated MMA (>300 nmol/L) indicates B12 deficiency at the cellular level, even if serum B12 appears normal.
Who Should Consider This Test
People with low-normal B12 levels needing clarification, those with neurological symptoms despite "normal" B12, vegetarians and vegans at risk for B12 deficiency, elderly individuals (B12 absorption declines with age), patients with malabsorption conditions, and anyone on metformin or proton pump inhibitors long-term.
Health Insights
Conditions Screened
Related Symptoms
When to Get Tested
No fasting required. MMA can be tested any time. It is most useful when serum B12 is in the "gray zone" (200-400 pg/mL) or when symptoms suggest B12 deficiency despite normal B12 levels.
Understanding Your Results
Normal MMA is <300 nmol/L. Elevated MMA (>300 nmol/L) with low or low-normal B12 confirms B12 deficiency. Elevated MMA with normal B12 suggests subclinical deficiency or early deficiency. Very high MMA with kidney disease may reflect impaired excretion rather than B12 deficiency—clinical correlation is needed.
What to Expect
After placing your order, you'll receive an email from Rupa Health (our lab order partner) within 24 business hours to sign a consent form and schedule your blood draw at a Quest Diagnostics location.
The blood draw typically takes just a few minutes. Results are usually available within 3-5 business days and will appear in your secure Justlabs dashboard.
Our results include reference ranges and easy-to-understand indicators showing whether your values are within normal limits.
Frequently Asked Questions
$37
Typical hospital cash price: $100–$200
+ $28 in standard lab & physician fees at checkout (no additional bills later)
$18 lab collection + $10 physician order
Need Help Choosing?
Not sure if this is the right test for you? Take our quick questionnaire.
Take the QuizRelated Tests
B12
Vitamin B12
$8
Measures B12 levels essential for nerve function, DNA synthesis, and red blood cell formation.
Biomarkers:
Vitamin B12
Homocysteine
Homocysteine
$23
Amino acid linked to cardiovascular risk when elevated. Also indicates B vitamin status.
Biomarkers:
Homocysteine
Folate
Folate, Serum
$7
Measures folic acid levels important for cell division, DNA synthesis, and preventing birth defects.
Biomarkers:
Folate
CBC w/ Diff
Complete Blood Count with Differential
$6
Comprehensive blood cell analysis including red cells, white cells, platelets, and white cell differential.
Biomarkers:
WBC, RBC, Hemoglobin +11 more
$37
+ $28 in fees