Table: B12-Related Laboratory Values

Serum B12 (sB12) is measured in both pmol/l and pg/ml. All sB12 values in this article are in pg/ml (using a conversion factor of 1 pg/ml = 1.35 * pmol/l¹).

U.S. Recommended Dietary Allowances for vitamin B12²
Age	Micrograms (µg, mcg)
0 - 5 months	0.4
6 - 11 months	0.5
1 - 3 years	0.9
4 - 8 years	1.2
9 - 13 years	1.8
14 years and older*	2.4
Pregnancy	2.6
Lactation	2.8
*The Food and Nutrition Board says, "Since 10 - 30% of older people may malabsorb food-bound B12, it is advisable for those older than 50 to meet their RDA mainly by consuming foods fortified with B12 or a B12-containing supplement."
Average daily dietary intake of B12 for adults in the USA²
men	5 µg
women	3.5 µg
Normal serum B12
range, newborns³	160 - 1300 pg/ml
range, adults^A	200 - 900 pg/ml
average	450 pg/ml
Breast Milk^B,4	180 - 300 pg/ml
Normal MCV Range⁵	80-96 fl
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 Homocysteine (HCY)	2.2 - 13.2 µmol/l⁹
Pre-treatment ranges in infants and children who have serious neurological problems due to genetic defects in B12 metabolism¹⁰
serum MMA	65-246 µmol/l
urine MMA	820 - 11,292 µmol/mmol Cr
serum HCY	trace - 89 µmol/l
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.

Notes for Appendix of B12 Values

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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.

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5. Stedman's Medical Dictionary, 26th ed. Baltimore: Williams & Wilkins, 1995.

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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.

10. Biancheri R, Cerone R, Schiaffino MC, Caruso U, Veneselli E, Perrone MV, Rossi A, Gatti R. Cobalamin (Cbl) C/D deficiency: clinical, neurophysiological and neuroradiologic findings in 14 cases. Neuropediatrics. 2001 Feb;32(1):14-22.

11. Halsted JA, Carroll J, Rubert S. Serum and tissue concentration of vitamin B12 in certain pathologic states. N Engl J Med. 1959;260:575-80.