Substantial changes in blood sugar—either low blood sugar (hypoglycemia) or high blood sugar (hyperglycemia)—can affect the excitability of nerve cells (neurons), allowing seizures to occur more easily. The brain relies almost entirely on glucose for energy, so it is very sensitive to blood sugar levels that are too high or too low. Slightly low blood sugar (mild hypoglycemia) and slightly high blood sugar (mild hyperglycemia) generally won’t cause seizures on their own in healthy individuals. However, research suggests that mild shifts can make seizures more likely in people who already have epilepsy or are prone to seizures.
Changes in blood sugar occur most frequently in people with diabetes. However, less common causes of hypoglycemia include the use of certain medications, excessive alcohol consumption, some critical illnesses, insulin overproduction, and endocrine deficiencies. Hyperglycemia may also be caused by certain medications (such as beta-blockers), illegal amphetamine drug use, and critical illness.
Sudden lowering of the blood sugar, usually from excess insulin administration (and, rarely, from a tumor in the pancreas), can cause a tonic-clonic seizure in anyone, whether or not they have a history of epilepsy. This kind of seizure (also called a grand mal seizure) involves the entire body, loss of consciousness, and violent muscle contractions. Other symptoms of hypoglycemia include sweating, fatigue, headache, anxiety, nausea, dizziness, alterations in vision, hunger, tremor, and confusion. Oral or intravenous glucose can be used to treat hypoglycemia, depending on the severity of the disorder. People who have diabetes with recurrent hypoglycemia should have their treatment regimen adjusted.
Having two or more seizures as the result of blood-sugar changes is not enough to diagnose someone with epilepsy, because these are considered "provoked" epileptic seizures as opposed to the "unprovoked" seizures associated with epilepsy.
For people with epilepsy, skipping meals or fasting for long periods has been linked to a higher risk of seizures in some people, especially those whose seizures are not well controlled. This may happen because of missed medication doses, fatigue, and changes in brain activity that occur when blood sugar drops.
However, eating foods that cause blood sugar to spike quickly—such as sugary drinks, white bread, or processed snacks—has also been linked to more seizures. Studies show that diets that keep blood sugar steady—such as low glycemic index and ketogenic diets—can help reduce how often seizures happen, even in people whose seizures don't respond well to medication. Researchers say further studies are needed to determine the best dietary approaches for each person, but managing blood sugar should be an important part of epilepsy care.
