Imbalances in blood sugar can directly trigger seizures, which are temporary disruptions of the brain’s electrical activity. This relationship exists because the brain is the most metabolically active organ, relying almost exclusively on a steady supply of glucose for fuel. When this delicate metabolic balance is thrown off, either by too little or too much glucose, the neurons cannot function normally. This leads to an abnormal, synchronized electrical discharge that manifests as a seizure.
How Glucose Fuels Brain Activity
The brain is an exceptionally demanding organ, consuming approximately 20% of the body’s total energy. This energy is provided almost entirely by glucose, which is transported across the blood-brain barrier to fuel cellular processes. Neurons require this constant energy supply to maintain their resting membrane potential and to power the ion pumps necessary for electrical signaling.
The brain lacks the ability to store significant amounts of glucose, unlike muscle or liver tissue. This means a continuous supply of glucose from the bloodstream is necessary to sustain normal function. When glucose levels fluctuate, the production of adenosine triphosphate (ATP), the primary energy currency of the cell, is immediately impacted. Stable blood glucose levels are a requirement for the continuous, orderly transmission of nerve impulses.
The Direct Threat of Low Blood Sugar (Hypoglycemia)
Hypoglycemia, defined as a blood glucose level typically below 70 milligrams per deciliter (mg/dL), is the most common cause of blood sugar-related seizures. The mechanism is a direct result of energy deprivation, as the brain begins to starve when its fuel source drops below a functional threshold. When glucose is insufficient, the neurons suffer energy failure, which destabilizes their electrical balance and leads to the release of excitatory amino acids.
This energy crisis results in disorganized and excessive firing of nerve cells, ultimately producing a seizure. Because the brain has no substantial glucose reserves, the progression from mild symptoms to a severe event can be rapid. Warning signs that precede a hypoglycemic seizure may include confusion, extreme hunger, muscle weakness, and a loss of coordination. If blood sugar continues to drop, the brain’s electrical systems can fail completely, leading to a loss of consciousness and convulsive activity.
When High Blood Sugar (Hyperglycemia) Becomes Dangerous
Seizures caused by high blood sugar (hyperglycemia) are less common than those caused by hypoglycemia and typically occur only in the context of severe metabolic crises. The two primary conditions are Diabetic Ketoacidosis (DKA) and, more frequently, Hyperosmolar Hyperglycemic State (HHS). HHS involves extremely elevated blood glucose, often exceeding 600 mg/dL, and profound dehydration.
The mechanism here is distinct, relating not to energy starvation but to osmotic imbalance. The massive concentration of glucose in the blood increases the plasma osmolality, which is the concentration of solutes in the blood. This hyperosmolar state pulls water out of the body’s cells, including brain cells, causing them to shrink. This cellular dehydration disrupts normal brain function, increasing neuronal irritability and leading to seizures. Seizures occur in up to 20% of patients experiencing HHS.
Immediate Steps During a Blood Sugar-Related Seizure
If a person is experiencing a seizure, the first priority is safety and injury prevention. Gently guide the person to the floor and move any nearby sharp or hard objects away from them. Time the seizure duration, as this information is important for medical personnel. It is crucial not to attempt to restrain the person or place anything in their mouth during the convulsive episode.
Once the convulsive movements have stopped, if the person is unconscious and a blood sugar-related cause is suspected, an emergency glucagon injection should be administered if available, as this hormone rapidly raises blood glucose. If the person is conscious and able to swallow safely, immediately provide a fast-acting source of glucose, such as 15 grams of glucose tablets or fruit juice. Call for emergency medical help immediately if the seizure lasts longer than five minutes, if the person has difficulty breathing, or if they do not regain consciousness shortly after the seizure ends.