If your body is very low on B6 (which is rare), you can get anemia, which is too few red blood cells. That would make you feel tired and weak. Anemia can also come from not having enough iron in your body. Shortages of other vitamins, like B12 and folate, also may cause it.
Seniors may run low on B6 if they don’t eat enough food or because their bodies don’t absorb nutrients as well as before. Kidney disease and other conditions that keep your small intestine from taking in nutrients also can be culprits. So can alcohol abuse. Some prescription medicines can also cause you to not have enough B6. If your doctor prescribes a new medicine, don't hesitate to ask about its overall effect on your body.