You can´t have beautiful, radiant skin if you are sleep deprived. During sleep, growth hormone is released, so you wake up looking your best. Lack of sleep causes dark circles to show up under your eyes and gives your complexion a grayish cast. What is actually happening is that fatigue causes the skin to pale so the bluish blood vessels beneath the skin´s surface become more pronounced. Research has shown that most adults function best with about eight hours of sleep each night. Lack of sleep raises levels of cortisol and glucose, causing health problems such as hypertension and type II diabetes, which speed up the aging process. Skin cells undergo repair and turnover more efficiently when you sleep, so if you don´t get enough sleep, your skin will suffer and look dull and lifeless.