Oral vitamin B 12 versus intramuscular vitamin B 12 for vitamin B 12 deficiency

Vitamin B deficiency is common, and the incidence increases with age. Most people with vitamin B deficiency are treated in primary care with intramuscular (IM) vitamin B . Doctors may not be prescribing oral vitamin B formulations because they may be unaware of this option or have concerns regarding its effectiveness. To assess the effects of oral vitamin B versus intramuscular vitamin B for vitamin B deficiency. We searched CENTRAL, MEDLINE, Embase, and LILACS, as well as the WHO ICTRP and ClinicalTrials.gov. The latest search date was 17 July 2017. We applied no language restrictions. We also contacted authors of relevant trials to enquire about other published or unpublished studies and ongoing trials. Randomised controlled trials (RCTs) comparing the effect of oral versus IM vitamin B for vitamin B deficiency. We used standard methodological procedures expected by Cochrane. Our primary outcomes were serum vitamin B levels, clinical signs and symptoms of vitamin B deficiency, and adverse events. Secondary outcomes were health-related quality of life, acceptability to patients, haemoglobin and mean corpuscular volume, total homocysteine and serum methylmalonic acid levels, and socioeconomic effects. We used GRADE to assess the quality of the evidence for important outcomes. We did not perform meta-analyses due to the small number of included trials and substantial clinical heterogeneity. Three RCTs met our inclusion criteria. The trials randomised 153 participants (74 participants to oral vitamin B and 79 participants to IM vitamin B ). Treatment duration and follow-up ranged between three and four months. The mean age of participants ranged from 38.6 to 72 years. The treatment frequency and daily dose of vitamin B in the oral and IM groups varied among trials. Only one trial had low or unclear risk of bias across all domains and outcome measures. Two trials reported data for serum vitamin B levels. The overall quality of evidence for this outcome was low due to serious imprecision (low number of trials and participants). In two trials employing 1000 μg/day oral vitamin B , there was no clinically relevant difference in vitamin B levels when compared with IM vitamin B . One trial used 2000 μg/day vitamin B and demonstrated a mean difference of 680 pg/mL (95% confidence interval 392.7 to 967.3) in favour of oral vitamin B . Two trials reported data on adverse events (very low-quality evidence due to risk of performance bias, detection bias, and serious im