Vitamin B12 plays a role in far more than energy. When levels drop, the effects can be felt across multiple body systems, from fatigue, low mood and poor sleep, to appetite changes Your body needs vitamin B12 to keep blood cells healthy and to make your nerves work right. Here are some signs that you're low on this vitamin: https: wb.md 44GSGRp Your body needs vitamin B12 to keep blood cells healthy and to make your nerves work right. Here are some signs that you're low on this vitamin: https: wb.md 44GSGRp Does Vitamin B12 Keep You Awake at Night? When to Take It Performance Lab The Best and Worst Forms of Vitamin B12 The Best Time to Take Vitamin B12 for Maximum Energy and Absorption