How to Recognize and Manage a Blood Sugar Spike


Blood sugar spikes are caused when a simple sugar known as glucose builds up in your 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 that glucose can enter them. Without insulin, glucose keeps floating around in your bloodstream with nowhere to go, becoming increasingly more concentrated over time.

When glucose builds up in your bloodstream, your blood glucose (blood sugar) levels rise. Long term, this causes damage to organs, nerves, and blood vessels.

Blood sugar spikes occur in people with diabetes because they’re unable to use insulin effectively.

Untreated high blood sugar can be dangerous, leading to a serious condition in diabetics called ketoacidosis.

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

Learning to recognize the symptoms of hyperglycemia (high blood sugar) can help you keep your diabetes in control. Some people with diabetes immediately feel the symptoms of high blood sugar, but others go undiagnosed for years 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 get worse the longer you go untreated.

Symptoms of a blood sugar spike include:

  • frequent urination
  • fatigue
  • increased thirst
  • blurred vision
  • headache
Blood sugar spike: What to do

It’s important to know the symptoms of hyperglycemia. If you suspect that you have high blood sugar, 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 only to use this method while closely following the recommendation of your doctor regarding your dose. If used improperly, insulin can cause hypoglycemia (low blood sugar).

Ketoacidosis and ketosis

It’s also important to understand the difference between ketoacidosis and ketosis.

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 turn to fat for fuel. 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, 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.

Ketoacidosis is an emergency that requires immediate treatment. You should 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

Blood sugar levels fluctuate all day long. When you eat food, particularly those foods that are 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 to your 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 adjusting
  • you’re using expired insulin
  • you’re not following your nutritional plan
  • you have an illness or infection
  • you’re using 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-controlled, but you’re experiencing unexplained blood sugar spikes, there might be a more acute cause.

Try keeping a record of all the food and drinks you consume. 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 two hours after eating. Even a few days of recorded information can help you and your doctor discover what’s causing your blood sugar spikes.

Common culprits include:

  • Carbohydrates. Carbs are the most common problem. Carbs get broken down into glucose very quickly. If you take insulin, talk to your doctor about your insulin-to-carb ratio.
  • Fruits.Fresh fruits are healthy, but they do contain a type of sugar called fructose that raises blood sugar. However, 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, especially when mixed with juice or soda. But it can also cause low blood sugars several hours later.
  • Lack of regular physical activity. Daily physical activity helps insulin work more effectively.Talk to your doctor about adjusting your medication to fit your workout schedule.
  • Over-treating low blood sugars. Over-treating is very common. Talk to your doctor about what to do when your blood glucose level drops so that you can avoid huge swings in blood glucose levels.

  1. Work with a nutritionist to develop a meal plan. Planning your meals will help you avoid unexpected spikes. You might also want to look at Diabetes Meal Plannning Made Easy from the American Diabetes Association (ADA).
  2. Start a weight loss program. Losing weight will help your body use insulin better. 
  3. 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. 
  4. Learn about the glycemic index. Research shows that 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
  5. Find healthy recipes. Check out this collection of recipes from the Mayo Clinic, or buy a diabetes cookbook from the ADA at
  6. Try an online meal planning tool. Healthy Plate from the Joslin Diabetes Center is one example.
  7. Practice portion control. A kitchen food scale will help you measure your portions better.
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