What to watch with B12 and sleep?

The link between vitamin B12 and sleep is not well established. B12 plays a role in melatonin synthesis and nerve function, which could indirectly affect sleep. Some observational studies suggest low B12 levels may be associated with sleep disturbances, but strong clinical evidence is lacking. If you have sleep issues, do not automatically take B12 supplements without confirming a deficiency. A blood test (e.g., holotranscobalamin) is advisable, especially for vegans, older adults, or those on proton pump inhibitors. High B12 doses (>1000 µg/day) are generally safe but may occasionally cause acne or dizziness. More importantly, focus on sleep hygiene, stress management, and checking for other deficiencies (iron, vitamin D, magnesium). The evidence for a direct sleep benefit from B12 is weak—most recommendations are based on practice and mechanistic reasoning.