Lightheadedness generally improves or completely subsides when the person lies down, explains WebMD. Repeated or ongoing lightheadedness may be the sign of a serious condition and requires medical attention.
Lightheadedness occurs when there's a decrease in blood flow to the brain, and it can develop for a variety of reasons. Sudden movements, dehydration, a drop in blood pressure or low blood sugar can cause lightheadedness, notes Healthline. Using tobacco products or alcohol may also cause someone to feel lightheaded. Serious conditions that may cause lightheadedness include heart attack, stroke, internal bleeding or shock. To treat serious cases of lightheadedness, a doctor must determine and treat the underlying cause.