When a person feels lightheaded, she may feel like the room is spinning around her or that she may faint. If she does faint, she loses consciousness for a brief amount of time. MedlinePlus explains that during a fainting episode, blood flow to the brain decreases. Certain conditions can cause lightheadedness and fainting.
Drop in Blood Pressure
A drop in blood pressure can cause people to feel dizzy and even lose consciousness. For example, MedlinePlus notes that bleeding and dehydration can cause a drop in blood pressure. People who are vomiting or have a fever or diarrhea can become dehydrated. Getting up too quickly after sitting or lying down cause cause blood pressure to drop. Overexerting, especially in hot conditions, and hyperventilating can also lead to a decrease in blood pressure. The American Academy of Family Physicians adds that becoming emotionally upset can cause fainting.
Drugs
Taking certain drugs, both those for medical conditions and those for recreational purposes, may result in becoming lightheaded or fainting. The "Physicians' Desktop Reference" points out that medications for heart conditions, such as beta blockers, digitalis, amidarone and quinidine, may cause these problems. Beta blockers can also treat the physical symptoms of anxiety. Medications for psychological disorders, such as phenothiazines and tricyclic antidepressants, may contribute to fainting. Blood pressure medications, such as diuretics, antihypertensive agents and nitrates may cause a drop in blood pressure that leads to lightheadedness and dizziness. MedlinePlus adds that medications for allergies or nasal congestion may also be causes. Recreational drugs that may cause lightheadedness and fainting include marijuana, alcohol and cocaine.
Medical Conditions
Different medical conditions may cause a person to feel lightheaded. Some of these conditions are not serious, such as the common cold. People who have the flu, allergies or hypoglycemia may become dizzy. But lightheadedness may be a sign of a more serious medical problem. MedlinePlus explains that a stroke, heart attack or abnormal heart rhythm may cause people to feel lightheaded. Diabetics may become lightheaded if they have a drop in blood sugar. The American Academy of Family Physicians points out that a drop in blood sugar can cause a non-diabetic to faint if he has not eaten for a while. Other medical conditions that may lead to lightheadedness and fainting include seizures and a pinched blood vessel in the neck.
Other Causes
MedlinePlus notes that a person may faint when having a bowel movement or when urinating. Standing still for too long or coughing very hard may also cause fainting. Other possible causes include stretching and severe pain.
