B12-Related Laboratory Values
Serum B12 is measured in both pmol/l and pg/ml. All serum B12 values in this article are in pg/ml (using a conversion factor of 1.35 pg/ml = 1 pmol/l (1).
|Average Daily B12 Intake of USA Adults2|
|Normal Serum B12|
|Range, newborns3||160 - 1300 pg/ml|
|Range, adultsA||200 - 900 pg/ml|
|180 - 300 pg/ml|
Normal MCV Range5
|Methylmalonic Acid (MMA)|
|Normal serum MMA (sMMA)||.07 - .27 µmol/l(6, 7)|
|Serum MMA cutoff in diagnosing B12 deficiency||.376 µmol/l7|
|Normal urine MMA (uMMA)||.58 - 3.56 µmol/mmol Cr8|
|Normal serum HCY||2.2 - 13.2 µmol/l9|
A - sB12 does not change more than 7% from week to week under normal
conditions (i.e. consistent intake, no disease)11.
B - Numbers vary widely depending on measurement methods and
differences in maternal stores and intake.
1. Tucker KL, Rich S, Rosenberg I, Jacques P, Dallal G, Wilson PW, Selhub J. Plasma vitamin B-12 concentrations relate to intake source in the Framingham Offspring study. Am J Clin Nutr. 2000 Feb;71(2):514-22. Link
2. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 2000.
7. Holleland G, Schneede J, Ueland PM, Lund PK, Refsum H, Sandberg S. Cobalamin deficiency in general practice. Assessment of the diagnostic utility and cost-benefit analysis of methylmalonic acid determination in relation to current diagnostic strategies. Clin Chem. 1999 Feb;45(2):189-98.
8. Rasmussen K, Moelby L, Jensen MK. Studies on methylmalonic acid in humans. II. Relationship between concentrations in serum and urinary excretion, and the correlation between serum cobalamin and accumulation of methylmalonic acid. Clin Chem. 1989 Dec;35(12):2277-80.
9. Loehrer FM, Schwab R, Angst CP, Haefeli WE, Fowler B. Influence of oral S-adenosylmethionine on plasma 5-methyltetrahydrofolate, S-adenosylhomocysteine, homocysteine and methionine in healthy humans. J Pharmacol Exp Ther. 1997 Aug;282(2):845-50.