Some causes of feeling lightheaded are positional change, dehydration and low blood sugar, states Healthline. Other causes include altitude sickness, allergies and colds, and the use of tobacco, alcohol or illegal drugs. More serious causes are heart conditions, strokes and internal bleeding.
Lightheadedness can occur when changing positions from seated to standing, reports Healthline. This happens as a result of a decrease in blood flow to the brain and a drop in blood pressure. People who are dehydrated have an increased chance of experiencing lightheadedness due to positional change. Drinking enough water and standing up slowly can improve positional lightheadedness.
People who have low blood sugar experience lightheadedness because the brain depends on blood sugar for energy, explains Drugs.com. Without sufficient energy, the brain is less able to function properly. Eating or drinking something sweet immediately resolves low blood sugar and the resulting symptom of lightheadedness.
Lightheadedness that results because of a heart attack or stroke requires immediate medical attention, states Healthline. Other symptoms present can indicate lightheadedness is a result of these serious conditions. These include unexplained sweating, nausea, facial drooping, chest pain or pressure, and shortness of breath. Patients with these symptoms should call 911 and not attempt to drive themselves to the hospital.