Blood sugar spikes occur when glucose, a simple sugar, builds up in the bloodstream. For people with diabetes, this happens because of the body’s inability to properly use glucose.

Most of the food you eat is broken down into glucose. Your body needs glucose because it’s the primary fuel that makes your muscles, organs, and brain work properly. But glucose can’t be used as fuel until it enters your cells.

Insulin, a hormone produced by your pancreas, unlocks cells so glucose can enter them. Without insulin, that glucose keeps floating around in your bloodstream with nowhere to go. It can become increasingly more concentrated over time.

When glucose builds up in your bloodstream, your blood glucose (blood sugar) levels rise. Over time, this can cause damage to organs, nerves, and blood vessels.

Blood sugar spikes occur in people with diabetes because their bodies are unable to use insulin effectively.

Keep reading to learn about the symptoms, causes, and treatment of blood sugar spikes.

Learning to recognize the symptoms of hyperglycemia (high blood sugar) can help you successfully manage your diabetes.

Some people with diabetes immediately feel the symptoms of high blood sugar. Others don’t because their symptoms are mild or vague.

Symptoms of hyperglycemia typically begin when your blood glucose goes above 250 milligrams per deciliter (mg/dL). Symptoms can worsen the longer it’s untreated.

Symptoms of a blood sugar spike may include:

  • frequent urination
  • fatigue
  • increased thirst
  • blurred vision
  • headache

A blood sugar spike happens when glucose builds up in the bloodstream and your blood sugar levels increase. This may happen after eating.

It’s important to know the early symptoms of high blood sugar, or hyperglycemia. Early testing and treatment can help prevent more severe symptoms.

Early signs of high blood sugar can include:

  • feeling thirsty
  • having a very dry mouth
  • urinating frequently
  • having blurred vision

If you suspect that you have high blood sugar, you can perform a finger stick to check your level.

Exercising and drinking water after eating, particularly if you’ve consumed a lot of starchy carbs, can help lower your blood sugar.

You can also use an insulin injection, but be careful to only use this method while closely following the recommendation of a doctor regarding your dose. If used improperly, insulin can cause hypoglycemia (low blood sugar).

If your blood sugar stays elevated for too long, you may develop diabetic ketoacidosis.

If high blood sugar levels go untreated for too long, glucose will build up in your bloodstream and your cells will be starved for fuel. Your cells will use fat for fuel instead.

When your cells use fat instead of glucose, the process produces a byproduct called ketones:

  • People with diabetes can develop diabetic ketoacidosis (DKA), a potentially deadly condition that causes the blood to become too acidic. Because of poorly functioning insulin in people with diabetes, ketone levels aren’t kept in check and can rise to dangerous levels very quickly. DKA can result in diabetic coma or death.
  • People without diabetes can tolerate certain levels of ketones in the blood. This state is known as ketosis. They do not go on to develop ketoacidosis because their bodies are still able to use glucose and insulin properly. Properly functioning insulin helps keep the body’s ketones levels stable.

Signs and symptoms of DKA

DKA is a medical emergency that requires immediate treatment. Call 911 or seek emergency medical attention if you experience any of the following signs and symptoms:

  • fruity-smelling breath or sweat
  • nausea and vomiting
  • severe dry mouth
  • trouble breathing
  • weakness
  • pain in the abdominal area
  • confusion
  • coma

The best way to manage high blood sugar is to check your blood sugar and take your medication as instructed. If you frequently experience blood sugar spikes, your doctor may change your medication routine.

You can also lower your blood sugar by exercising. However, if your blood sugar level is repeatedly above 240 mg/dL, check your urine for ketones using a test kit.

If you do have ketones, do not exercise. In this case, exercising may make your blood sugar levels go even higher.

If you think you may have DKA, you can test your urine for ketones using a test kit. If ketones are high, call a doctor and seek emergency medical attention immediately.

Blood sugar levels fluctuate all day long. When you eat food, particularly foods high in carbohydrates like bread, potatoes, or pasta, your blood sugar will immediately begin to rise.

If your blood sugar is consistently high, you need to talk with a doctor about improving your diabetes management. Blood sugar rises when:

  • you’re not taking enough insulin
  • your insulin isn’t lasting as long as you think it is
  • you’re not taking your oral diabetes medication
  • your medication dosage needs to be adjusted
  • you’re using expired insulin
  • you’re not following your nutritional plan
  • you have an illness or infection
  • you’re taking certain medications, like steroids
  • you’re under physical stress, such as an injury or surgery
  • you’re under emotional stress, such as trouble at work or home, or with money problems

If your blood sugar is usually well managed but you’re still experiencing unexplained blood sugar spikes, there might be an acute, or more recent, cause.

Try keeping a record of all the food and drinks you consume. Then check your blood sugar levels according to your doctor’s recommendations.

It’s common to record your blood sugar reading first thing in the morning, before you’ve eaten, and then again 2 hours after eating.

Even a few days of recorded information can help you and your doctor learn what’s causing your blood sugar spikes.

Common reasons for blood sugar spikes include:

  • Carbohydrates: Carbs get broken down into glucose very quickly. If you take insulin, talk with your doctor about your insulin-to-carb ratio.
  • Fruits: Fresh fruits are considered healthy choices for people with diabetes by the American Diabetes Association (ADA), but they do contain a type of sugar called fructose that raises blood sugar. Fresh fruits are a better choice than juice, jellies, or jams.
  • Fatty foods: Fatty foods can cause what’s known as the “pizza effect.” Taking pizza as an example, carbohydrates in the dough and sauce will raise your blood sugar immediately, but the fat and protein won’t affect your sugars until hours later.
  • Juice, soda, electrolyte drinks, and sugary coffee drinks: These all affect your sugars, so don’t forget to count the carbs in your drinks.
  • Alcohol: Alcohol raises blood sugar immediately, too, especially when mixed with juice or soda. It can also cause low blood sugars several hours later.
  • Lack of regular physical activity: Daily physical activity helps insulin work more effectively. Talk with your doctor about adjusting your medication to fit your workout schedule.
  • Overtreating low blood sugars: Overtreating is very common. Talk with your doctor about what to do when your blood glucose level drops so you can avoid swings in your blood glucose levels.

There are many ways to prevent blood sugar spikes. Consider adding the following to your diabetes management plan:

  • Work with a nutritionist to develop a meal plan: Planning your meals can help avoid unexpected spikes. You might also want to look at meal planning resources from the ADA.
  • Start a weight loss program, if needed: Losing weight can help your body use insulin better. Talk with your doctor about weight management, and whether they recommend you lose weight to manage your diabetes.
  • Learn how to count carbs: Carb counting helps you keep track of how many carbohydrates you’re consuming. Setting a maximum amount for each meal helps stabilize blood sugar. Check out the ADA’s resources on counting carbs and guidebook “Choose Your Foods: Count Your Carbs,” which is available for purchase on the ADA online store.
  • Learn about the glycemic index: Not all carbs are created equal. The glycemic index (GI) measures how different carbs may affect blood sugar. Foods with a high GI rating can affect blood sugar more than those with a lower rating. You can search for low GI foods through, from the University of Sydney.
  • Find healthy recipes or an online meal planning tool: You can try the “diabetes plate method.”
  • Measure your portions: A kitchen food scale can help you measure your portions better.
  • Be more active: Exercising regularly and limiting your time spent sitting can help keep your blood sugar levels in check. Try going on walks, taking a fun exercise class, or integrating exercise into activities you already do — like lifting weights while watching your favorite show.
  • Walk after a meal: Walking for about 15 minutes after a meal may help manage blood glucose levels in people with diabetes.

Long-term diabetes complications typically result from having elevated blood sugar levels over a long period of time. Diabetes complications may develop slowly over the course of many years before symptoms appear.

Chronic high blood sugar increases the likelihood of serious diabetes complications like heart disease, blindness, neuropathy, and kidney failure.

Untreated high blood sugar could also develop into ketoacidosis. This is an emergency condition that could lead to diabetic coma or death.

When blood sugar levels remain high for a long period of time, your major organs and body systems may be affected.

Other complications of diabetes can include:

Eye problems

People with diabetes have an increased risk of developing eye problems, including:

  • cataracts
  • retinopathy
  • glaucoma

A cataract is a thickening and clouding of the lens of the eye that can make your vision blurry and impair night vision.

Diabetic retinopathy is caused by damage to the blood vessels of the retina from abnormal growth of small blood vessels, which are believed to be related to untreated high blood sugar levels over a long period of time. Symptoms might not appear at first but can eventually lead to blindness.

Diabetic retinopathy can increase your risk of glaucoma. In this disease, pressure builds up in the eye, decreasing blood flow and causing damage to the retina and optic nerve.

Kidney disease

Diabetic nephropathy is a progressive kidney disease in which the kidneys, which are responsible for filtering the body’s waste, stop functioning. It happens when high blood sugar levels damage the blood vessels in the kidneys.

You may not have symptoms in the early stages of kidney disease, but it can eventually progress to kidney failure.

Nerve damage (diabetic neuropathy)

Diabetic neuropathy, or nerve damage, is a serious complication of diabetes. It’s caused by high blood sugar levels over a long period of time.

Symptoms typically appear gradually and develop over the course of decades.

There are four main types of neuropathy that affect people with diabetes:

  • peripheral neuropathy
  • autonomic neuropathy
  • proximal neuropathy
  • focal neuropathy

Heart and blood vessel diseases

Over time, high blood sugar can damage the blood vessels and nerves in your heart. People with diabetes also have an increased risk of developing cardiovascular diseases, including heart attack and stroke.

Untreated high blood sugar can also block blood vessels. This can lead to infections and foot ulcers. In serious cases, it can lead to amputation of a toe, foot, or lower leg.

Periodontal disease

People with diabetes have an increased risk of developing gum disease, also called periodontal disease.

High blood sugar levels can lead to an increased amount of sugar in the mouth, affecting overall oral health. People with diabetes are more likely to produce more plaque, have less saliva, and have poorer circulation in the gums.

People with diabetes experience blood sugar spikes because of their body’s inability to use glucose effectively.

Untreated high blood sugar can be dangerous. It can lead to a life threatening condition called ketoacidosis. It can also increase the likelihood of developing serious complications like heart disease, blindness, neuropathy, and kidney failure.

Following your medication routine, regularly testing your blood sugar, and maintaining a balanced diet and regular exercise routine can help you manage blood sugar spikes and reduce the risk of complications in the future.