A single seizure usually lasts less than 3 minutes and is not followed by a second seizure. Any normally healthy person can have a single seizure under certain conditions. For instance, a sharp blow to the head may cause a seizure.

A first seizure may also be a sign of a serious medical problem, such as:

• A stroke. A stroke (cerebrovascular accident, or CVA) occurs when the blood flow to part of the brain is greatly reduced or blocked.
• An extremely low blood sugar level.
• Electrolyte imbalances. Electrolytes are minerals that are found naturally in the body. They are needed to keep the body's balance of fluids at the proper level and to maintain normal functions, such as heart rhythm, muscle contraction, and brain function.
• Infections of the brain and spinal cord (meningitis or encephalitis).
• Eclampsia, a pregnancy-related blood circulation problem that causes high blood pressure.
• Kidney disease or failure.
• Withdrawal from alcohol or medicines, including illegal drugs.
• Eating, drinking, breathing, or injecting certain poisons or illegal drugs.
• A brain tumor or previous brain surgery.
• An overdose or sensitivity to many prescription or nonprescription medicines.
• A previous head injury.
• Low oxygen level (hypoxemia).
• Severe high blood pressure (hypertension).
• Liver disease.

A first seizure requires immediate medical attention.