Vitamin B12 deficiency can be caused by poor diet or malabsorption, leading to fatigue, muscle weakness, and memory problems.

This comprehensive review examines vitamin B12 absorption, physiological roles, deficiency states, and dietary sources, with ...

Vitamin B6 can also influence serotonin and dopamine levels, which can impact your sleep if taken too late, Keatley says. “For individuals using a B-complex supplement, morning with breakfast is often ...