Methylmalonic acid (MMA) optimal range and reference range

Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026

Sera's bands for Methylmalonic acid (MMA):

Optimal 0 – 271 nmol/L (0 – 32 μg/L); sufficient 271 – 370 nmol/L (32 – 43.7 μg/L); out of range below 0 or above 370 nmol/L.

Evidence grade: Published reference interval. A band that primarily reflects a published adult laboratory or population reference interval. It is not necessarily applicable to every assay or laboratory.

All units

Unit	Optimal	Sufficient	Out of range
nmol/L	0 – 271	271 – 370	below 0 or above 370
μg/L	0 – 32	32 – 43.7	below 0 or above 43.7
ng/mL	0 – 32	32 – 43.7	below 0 or above 43.7

What the evidence says

MMA rises when vitamin B12 is too low for the cells to use, so it is read as a functional test of B12 status, most useful when serum B12 is borderline. The acceptable band ends at 370 nmol/L, the cut-off a large US laboratory describes as generally agreed for elevated MMA; in US survey data a result above about 376 was more than 99% specific for inadequate B12 status. The optimal band ends at 271 nmol/L, the cut-off US population studies have long used; a CDC analysis suggests 229 nmol/L when screening people at higher risk of deficiency. MMA also rises with age and with reduced kidney function independently of B12, so check eGFR before reading a raised result as B12 deficiency. A low result has no clinical meaning.

Assay: Results differ meaningfully between platforms and methods. Compare against the interval printed by the issuing laboratory before acting on a borderline value.

Sources

Methylmalonic Acid, Serum or Plasma — Labcorp, 2026 · Laboratory / reference-interval sourceReference interval 0 to 378 nmol/L, with 370 nmol/L named as the generally agreed cut-off for elevated MMA; about 2% of the US population and 7% of elderly people are above it. Matches Sera's acceptable upper edge.
The Diagnostic Accuracy of Methylmalonic Acid to Detect Inadequate Vitamin B-12 Status Relative to 3cB-12 Was Higher Compared with That of Total Cobalamin and Total Homocysteine in a Cross-Sectional Survey of Apparently Healthy US Adults — Mineva EM, Sternberg MR, Pfeiffer CM — Current Developments in Nutrition, 2026 · Peer-reviewed publicationIn US adults with normal kidney function, MMA above 376 nmol/L was over 99% specific for inadequate B12 status and suits healthy populations; above 229 nmol/L was the most accurate cut-off overall and suits screening of higher-risk groups. Supports 370 as the acceptable upper edge and shows 150 is too strict for the optimal edge.
High folic acid or folate combined with low vitamin B-12 status: potential but inconsistent association with cognitive function in a nationally representative cross-sectional sample of US older adults participating in the NHANES — Bailey RL, Jun S, Murphy L, et al. — The American Journal of Clinical Nutrition, 2020 · Peer-reviewed publicationUS national survey analysis defines low B12 status as MMA above 271 nmol/L or serum B12 below 150 pmol/L. This is the traditional cut-off proposed as the new optimal upper edge.
Folate, vitamin B-12, and cognitive function in the Boston Puerto Rican Health Study — Boumenna T, Scott TM, Lee JS, Palacios N, Tucker KL — The American Journal of Clinical Nutrition, 2021 · Peer-reviewed publicationA second US cohort using the same definition: B12 deficiency is plasma B12 below 148 pmol/L or MMA above 271 nmol/L.
Methylmalonic acid (serum) — University Hospitals Sussex NHS Foundation Trust, 2025 · Laboratory / reference-interval sourceBelow 0.29 µmol/L (290 nmol/L) is not indicative of B12 deficiency; 0.29 to 0.70 suggests it; above 0.70 is consistent with overt deficiency. MMA also rises with renal impairment. Shows a UK laboratory treats results up to 290 nmol/L as unremarkable.
Methylmalonic Acid (MMA) Test — MedlinePlus, US National Library of Medicine, 2024 · Government / public-health guidanceGives no numbers, but states that a low MMA is uncommon and not a health problem, which is why Sera's band starts at zero and a low result is never flagged.

What Methylmalonic Acid (MMA) measures

A substance that builds up in the body when cells do not have enough usable vitamin B12. It is the most sensitive sign of true B12 status.

Blood B12 can look normal even when your cells are short of it, and raised MMA catches this hidden shortfall. It is especially useful for vegans, vegetarians, older adults, and anyone with nerve symptoms despite a normal B12. Read it together with B12 and homocysteine.

Related vitamins & minerals markers

See Methylmalonic acid (MMA) in the full list of biomarker ranges

This page is a reference for practitioners, not medical advice. Sera's bands are practitioner targets for structured review, not diagnostic thresholds, and Sera does not diagnose or recommend treatment. Read a result alongside the interval printed by the issuing laboratory and the client's history and symptoms. Range set: Sera Production, version 1.0, last reviewed November 9, 2026.