Are you lacking in B12? 

Vitamin B12 deficiency causes tiredness, weakness, constipation, loss of appetite, and megaloblastic anemia (a fancy name for large, immature red blood cells). Nerve problems, such as numbness and tingling in the hands and feet, can also occur. Other symptoms of vitamin B12 deficiency include problems with balance, depression, confusion, dementia, poor memory, and soreness of the mouth or tongue as well as damage to the nervous system.