Lightheadedness makes a person feel that he or she is about to faint or pass out. It is caused by a momentary drop in blood pressure and blood flow to the head.
Nausea or vomiting sometimes accompanies lightheadedness. Symptoms usually improve or go away after lying down.
It is common to feel lightheaded occasionally. Lightheadedness often occurs when a person gets up too quickly from a seated or lying position (orthostatic hypotension).
Unlike vertigo, lightheadedness does not produce a sensation of movement. Vertigo causes a spinning or whirling sensation that may lead to nausea or vomiting, loss of balance, trouble walking or standing, and falling.