Hyperglycemia-Related Seizures

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Hyperglycemia is the medical term for high blood sugar. Although it’s a common complication of diabetes, hyperglycemia can happen to anyone. If left untreated, high blood sugar can lead to hyperglycemia-related seizures. 

About 25% of people with diabetes will experience seizures. Most often, these are caused by low blood sugar. However, if left untreated, hyperglycemia can also cause seizures.

Learn more about these seizures and how to prevent them below. 

person having a seizure

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Types of Hyperglycemia That Cause Seizures

Two types of hyperglycemia can cause seizures. These include:

  • Nonketotic hyperglycemia
  • Ketotic hyperglycemia

Nonketotic Hyperglycemia

One of the most common causes of seizures related to high blood sugar is nonketotic hyperglycemia (NKH). This is also called hyperosmolar hyperglycemic syndrome (HHS).

NKH occurs most often in people with type 2 diabetes, but it can also occur in people who do not have diabetes.

With this condition, blood sugar levels are up to 10 times higher than healthy levels. The blood becomes very concentrated with glucose and salt, which can affect the function of vital organs, including the brain. Up to 25% of people with NKH will have a seizure.

NKH occurs most often in older people with type 2 diabetes. Risk factors include:

  • Skipping or stopping your diabetes medication
  • Infection or other illness
  • Stress
  • Cardiovascular disease
  • Dehydration

About half of people who experience a seizure brought on by NKH will die. It’s important to immediately seek help if you experience a change in consciousness or if you get an abnormally high reading when testing your blood glucose level. 

Ketotic Hyperglycemia

The second type of hyperglycemia that can lead to seizures is ketotic hyperglycemia. This is most common in people with type 1 diabetes.

When blood sugar is elevated, the body can’t use it for fuel. Instead, it starts burning fat. As fat is burned, it releases chemicals called ketones into the bloodstream.

When these ketones build up in high concentrations, they can become poisonous, turning the blood acidic. This is a condition known as diabetic ketoacidosis (DKA).

People who experience DKA are at higher risk of seizures.

How Hyperglycemia Can Cause Seizures

When blood sugar is extremely high due to hyperglycemia, the neurons in the brain become overstimulated. This can cause the brain to “short circuit,” leading to a seizure.

It’s best to intervene with high blood sugar before your glucose becomes high enough to lead to a seizure. However, oftentimes people don’t notice the symptoms of hyperglycemia until a seizure is imminent.

Signs of Seizure

The signs that a seizure will occur very soon include:

  • Sweating
  • Vision changes
  • Confusion or hallucinations

If you feel a seizure coming on, try to lie down and call 911. Hyperglycemia-related seizures can last for seconds or minutes, and always warrant medical attention. 

Related Complications

Hyperglycemia, particularly NKH, can have complications outside of causing seizures. Recognizing these can help you identify NKH and possibly help you avoid a seizure by seeking treatment immediately. 

Complications related to NKH include:

  • Nonketotic hyperglycemic hemichorea: This condition is characterized by involuntary movements, including twisted and writhing movements, as well as jerking of the limbs. With NKH, these symptoms come on suddenly and can resolve when insulin is administered to lower blood sugar.
  • Nonketotic hyperosmolar coma: In rare cases, NKH can lead to a person losing consciousness and dropping into a diabetic coma. Coma can lead to irreversible brain damage, so it’s critical to seek emergency treatment.


When a seizure occurs, you should get medical treatment immediately. Remember that NKH is a potentially fatal condition that requires medical attention. If you experience a seizure, it indicates that your condition is severe. 

Administering Insulin

For seizures caused by high blood sugar, treatment involves administering insulin to reduce blood sugar. However, this should be done under medical supervision, since giving too much too quickly can cause dangerous complications.

After the immediate condition has been treated, you should speak with your healthcare provider and a nutritionist about long-term approaches to help you avoid episodes of NKH and seizures caused by high blood sugar in the future.

Hyperglycemia can have very severe, even fatal consequences. Taking steps to avoid high blood sugar, especially if you have diabetes, is critical for your health and wellbeing.

A Word From Verywell

Experiencing a diabetic seizure can be terrifying, both for the person who is seizing and for their loved ones. It can also lead to long-term health complications. 

Prevention is truly the best medicine for hyperglycemia-related seizures. Taking your medications as prescribed, eating healthy, exercising, and maintaining regular healthcare provider visits can all help control your blood sugar. 

However, sometimes hyperglycemia or NKH can occur suddenly. These conditions can be brought on by stress, infection, or illness. For this reason, everyone—especially people with diabetes—should know the early signs of hyperglycemia, including excessive thirst, frequent urination, and confusion

Always reach out to your healthcare provider if you suspect you might be experiencing hyperglycemia. There is no shame in being wrong, but if you’re right, making that call could save your life.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Yun C, Xuefeng W. Association between seizures and diabetes mellitus: a comprehensive review of literatureCurr Diabetes Rev. 2013;9(4):350-354. doi:10.2174/15733998113099990060

  2. Stafstrom CE. Hyperglycemia lowers seizure thresholdEpilepsy Curr. 2003;3(4):148-149. doi:10.1046/j.1535-7597.2003.03415.x

  3. MedlinePlus. Diabetic hyperglycemic hyperosmolar syndrome

  4. Radiopaedia. Non-ketotic hyperglycemia seizure.

  5. Epilepsy Foundation. Nonketotic hyperglycemia

  6. American Diabetes Association. DKA (ketoacidosis) and ketones.

  7. Radiopaedia. Non-ketotic hyperglycemic hemichorea.

  8. Centers for Disease Control and Prevention. Manage blood sugar.

By Kelly Burch
Kelly Burch is has written about health topics for more than a decade. Her writing has appeared in The Washington Post, The Chicago Tribune, and more.