Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency: a systematic review of randomized controlled trials.
BACKGROUND
Vitamin B(12) deficiency is common, increasing with age. Most people are treated in primary care with intramuscular vitamin B(12). Several studies have reported equal efficacy of oral administration of vitamin B(12).


OBJECTIVE
We set out to identify randomized controlled trial (RCT) evidence for the effectiveness of oral versus intramuscular vitamin B(12) to treat vitamin B(12) deficiency.


METHODS
We conducted a systematic review searching databases for relevant RCTs. Outcomes included levels of serum vitamin B(12), total serum homocysteine and methylmalonic acid, haemoglobin and signs and symptoms of vitamin B(12) deficiency.


RESULTS
Two RCTs comparing oral with intramuscular administration of vitamin B(12) met our inclusion criteria. The trials recruited a total of 108 participants and followed up 93 of these from 90 days to 4 months. In one of the studies, mean serum vitamin B(12) levels were significantly higher in the oral (643 +/- 328 pg/ml; n = 18) compared with the intramuscular group (306 +/- 118 pg/ml; n = 15) at 2 months (P < 0.001) and 4 months (1005 +/- 595 versus 325 +/- 165 pg/ml; P < 0.0005) and both groups had neurological responses. In the other study, serum vitamin B(12) levels increased significantly in those receiving oral vitamin B(12) and intramuscular vitamin B(12) (P < 0.001).


CONCLUSIONS
The evidence derived from these limited studies suggests that 2000 microg doses of oral vitamin B(12) daily and 1000 microg doses initially daily and thereafter weekly and then monthly may be as effective as intramuscular administration in obtaining short-term haematological and neurological responses in vitamin B(12)-deficient patients.
Department of General Practice, Cardiff University, Wales, UK.
Christopher C
CC
Butler
Josep
J
Vidal-Alaball
Rebecca
R
Cannings-John
Andrew
A
McCaddon
Kerenza
K
Hood
Alexandra
A
Papaioannou
Ian
I
Mcdowell
Andrew
A
Goringe
D000284:Administration, Oral; D000752:Anemia, Pernicious / Q000188:drug therapy; D006801:Humans; D007273:Injections, Intramuscular; D016032:Randomized Controlled Trials as Topic; D014805:Vitamin B 12 / Q000008:administration & dosage*; D014806:Vitamin B 12 Deficiency / Q000188:drug therapy*; D014803:Vitamin B Complex / Q000008:administration & dosage*
D014803:Vitamin B Complex; D014805:Vitamin B 12