Vitamin B12 (Cobalamin)

This page cites nine publications from 2005 to 2026, and most of them describe people rather than laboratory models. Two are trials of oral cyanocobalamin, one in children with nutritional deficiency and one a dose-finding study in older adults. Five more are clinical or observational reports: a paediatric comparison of sublingual methylcobalamin with intramuscular injection, a prospective cohort in pernicious anaemia, a study of metformin users, a series of children with deficiency anaemia given oral methylcobalamin, and a single case report. The other two are a systematic review of deficiency after bariatric surgery and a review of industrial B12 production.

In children, the 2018 trial reported that oral cyanocobalamin restored B12 status, the 2017 series described adequate early responses to oral methylcobalamin, and the 2025 study compared sublingual methylcobalamin with intramuscular cyanocobalamin and reported similar responses. In older adults, the dose-finding trial set out to identify the lowest oral dose that normalised mild deficiency, and the 2024 cohort reported that oral cyanocobalamin raised B12 status in people with pernicious anaemia. The metformin study found no significant difference in serum B12 between users and non-users, with or without diabetes, and concluded that universal screening could not be recommended. The case report described severe deficiency that mimicked thrombotic thrombocytopenic purpura, and the bariatric review addressed the risk of deficiency after surgery and ways to prevent it.

The human studies here are about deficiency, its causes and its correction, so none describes effects in people whose B12 status is normal. Several are observational, one is a single case, and the manufacturing review does not study B12 in people at all. The entries shown here give no sample sizes or follow-up periods, so the scale of each study cannot be judged from this page.