What’s a better test for vitamin B12 deficiency: methylmalonic acid (MMA) or homocysteine?

By William Aird

Both markers are highly sensitive, but MMA is more specific (for example, homocysteine levels may also be increased in patients with folate deficiency). MMA values considered high vary from 0.28 to 0.75 mcmol/L.

2014 British Committee for Standards in Haematology guidelines for the diagnosis and treatment of cobalamin and
folate disorders:

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