Lightheadedness often occurs as a result of pressure changes when blood flow to the brain decreases, according to Healthline. This can be caused by standing suddenly from a seated position or by being dehydrated. Lightheadedness can also be caused by low blood sugar, drug use, allergies and altitude changes.
People who use alcohol, prescription medications or over-the-counter remedies or experience an illness such as the cold or flu can experience lightheadedness, explains Healthline. Underlying health complications may also cause lightheadedness, such as internal bleeding, heart disease, rapid drops in blood pressure and stroke. If the sensation of dizziness is accompanied by excessive bleeding, chest pain, nausea, sweating, difficulty breathing or facial drooping, it is imperative to call an ambulance or have someone provide a ride to the emergency room as soon as possible. It is common for benign cases of lightheadedness to resolve on their own after time.
Healthline recommends staying hydrated and avoiding excessive alcohol and cigarette use. A doctor must determine if prescription medications are the cause of dizziness, and these treatments should not be stopped until instructed to do so by a medical professional. In some cases, a person's dizziness may be caused by a more serious condition known as vertigo. If this is the case, a doctor is able to perform diagnostic tests and recommend a proper course of treatment, notes MedicineNet.