How are B12 and sleep related?

The relationship between vitamin B12 and sleep is not fully established, but plausible biological links exist. B12 is crucial for homocysteine metabolism, methylation, and the synthesis of neurotransmitters like serotonin and melatonin, which regulate circadian rhythms. Deficiency can cause fatigue, neurological issues, and potentially sleep disturbances. Some observational studies suggest low B12 levels are associated with insomnia or shorter sleep duration, but results are inconsistent. High-dose B12 supplementation is sometimes used off-label for sleep disorders, but evidence is weak. MyBody-X tests can detect deficiency, but they are not diagnostic for sleep problems. A medical workup is essential for persistent sleep issues. Evidence rating: mixed – mechanistic plausibility and some human data, but no strong clinical trials.