What happens if I wake up during deep sleep?

Waking during deep sleep can cause sleep inertia, a temporary period of grogginess, confusion and reduced alertness. You may feel heavy, disoriented or tempted to fall straight back asleep. This feeling usually improves within several minutes, although it can sometimes last longer if you are sleep deprived. Deep sleep is concentrated more heavily in the earlier part of the night, but it can occur at other times as well. Waking during it is not normally harmful. The bigger concern is repeatedly interrupting deep sleep through noise, alcohol, breathing problems or an irregular schedule. Avoid cutting total sleep simply to reach a predicted cycle ending. Consistent wake times, morning light, movement and hydration may help you become alert more quickly.