Hyperglycemia (high blood sugar) is the main sign of diabetes. Insufficient insulin production, resistance to the action of insulin, or both can cause diabetes to develop.

When a person eats carbohydrates, the body breaks them down into simple sugars that enter the bloodstream. The pancreas then releases insulin, a hormone that allows the body’s cells to absorb sugar from the blood and use it to produce energy.

If the body does not make any insulin, if it does not make enough insulin, or if the cells cannot use the insulin correctly, blood sugar levels increase.

In this article, we look at the relationship between hyperglycemia and diabetes.

People with prediabetes will have blood sugar levels that are higher than expected but not as high as the levels would be in diabetes. However, people with prediabetes are still at risk of developing diabetes.

Doctors tend to diagnose prediabetes at a fasting glucose level of 100 milligrams per deciliter (mg/dL) and diabetes at 126 mg/dL.

People with prediabetes would score 140 to 199 on an oral glucose tolerance test, while those with diabetes would score 200 or higher.

Diabetes causes high blood sugar levels through two possible mechanisms: insufficient insulin production in the pancreas and resistance to the action of insulin elsewhere in the body.

In type 1 diabetes, the immune system destroys the insulin-producing cells in the pancreas. In type 2 diabetes, the body’s cells resist the action of insulin and, as a result, the pancreas does not respond appropriately and does not release enough insulin.

People with type 1 diabetes need to take supplementary insulin to regulate their blood sugar. Some people with type 2 diabetes might need insulin, but they might also take noninsulin oral medications.

All people with diabetes, regardless of type, should monitor their blood sugar levels to make sure they stay within a safe range.

Several factors can worsen hyperglycemia in people with diabetes, such as:

People with diabetes may need to take extra medication to keep their blood sugar levels stable during times of illness or stress.

Exercising can cause blood glucose to decrease or increase, depending on the type of workout. Moderate to intense workouts, such as sprints and heavy weightlifting, can produce stress hormones such as adrenaline. Adrenaline can increase blood sugar levels.

Doing moderate-intensity aerobic workouts or circuit weight training can help. People with diabetes can try practices such as mindful breathing or meditation before or during a workout to lower stress hormones.

Shifting workouts to later in the day can also help since blood sugar levels naturally rise in the morning. A surge of hormones that occurs roughly between 4 a.m. and 5 a.m. pushes the blood sugar up. This is called the dawn phenomenon.

Hyperglycemia can be dangerous because it often does not cause symptoms until glucose levels are very high.

People who have had type 2 diabetes for several years may not have any symptoms when their blood sugar is high. Many people have undiagnosed type 2 diabetes.

Prolonged hyperglycemia increases the risk of diabetes-related complications such as kidney disease, eye disease, and neuropathy.

Typical signs and symptoms of hyperglycemia include:

Potential complications

One possible complication of unmanaged diabetes is diabetic ketoacidosis (DKA). In DKA, ketones, which are waste products of the body’s breakdown of fats, build up in the blood.

Ketoacidosis develops in response to an inability to use existing glucose in the bloodstream. Without insulin, or if the body is highly resistant to insulin, the body cannot use sugar as energy.

This causes the breakdown of fats for energy, creating ketones as a waste product. Both resistance to insulin and a lack of insulin in the body can cause DKA.

People with type 1 diabetes are most at risk of DKA. Ketoacidosis is rare in people with type 2 diabetes, but it can occur.

DKA is a life threatening condition and requires immediate treatment. Symptoms include:

  • fruity-smelling breath
  • nausea and vomiting
  • shortness of breath
  • thirst
  • a dry mouth
  • weakness
  • confusion
  • coma
  • stomach pain
  • nausea
  • vomiting

Another possible complication of unmanaged diabetes is hyperosmolar hyperglycemic syndrome. This occurs when the blood sugar levels become very high.

Without treatment, hyperosmolar hyperglycemic syndrome can be life threatening and lead to severe dehydration and possibly coma.

This syndrome is quite rare and usually occurs in older adults with type 2 diabetes. It is most likely to occur when people are ill and have difficulty staying hydrated.

Typically, a co-occurring health condition such as infection or stroke causes hyperglycemic hyperosmolar syndrome in diabetes.

Long-term complications

Hyperglycemia due to unmanaged diabetes can cause serious long-term complications such as:

  • blood vessel damage that increases the risk of heart disease and stroke
  • nerve damage
  • kidney damage or failure
  • damage to the blood vessels of the retina, which may lead to vision loss or blindness
  • cataracts (clouding of the lenses of the eyes)
  • foot problems that can lead to serious infections
  • bone and joint problems
  • skin problems, including infections and nonhealing wounds
  • tooth and gum infections

A person can monitor their blood sugar at home with the help of a fingerstick or a continuous glucose monitoring system.

During a doctor’s visit, a healthcare professional may draw blood to determine a person’s exact blood sugar level. An A1C test indicates average blood sugar levels during the previous 3 months.

The A1C test measures the percentage of glucose in the bloodstream that is bound to hemoglobin, the oxygen-carrying protein in red blood cells. A score higher than 6.5 suggests that a person has diabetes.

The Centers for Disease Control and Prevention (CDC) suggests the following blood sugar targets for most adults with diabetes who are not pregnant:

  • Before a meal: 80 to 130 mg/dL
  • Around 2 hours after the beginning of the meal: less than 180 mg/dL

Ranges can vary depending on age and any underlying medical conditions, such as heart, lung, or kidney disease. Ranges also vary for people who are pregnant or experiencing complications from diabetes.

Anyone who has diabetes should use a glucose meter to monitor their blood sugar at home and ensure that they stay within their target range. Home monitoring allows people to quickly notice any potentially harmful changes and immediately report problems to a healthcare professional.

Over-the-counter urinary ketone level test kits are also available to determine the presence of DKA.

If a person is experiencing any of the symptoms above, a positive test result means that their body may be in the early stages of DKA, and they should consider seeking treatment immediately.

If a person with diabetes is experiencing symptoms of hyperglycemia, a doctor can adjust their medication regimen accordingly. This can return the person’s blood sugar to a safe level.

An emergency room visit might be necessary if certain symptoms occur or do not resolve, including:

  • symptoms that suggest DKA
  • blood sugar levels that do not respond to home management
  • a co-occurring condition, such as a stroke

Prevention

In addition to talking with a doctor about managing their blood sugar levels, people can take the following steps to avoid hyperglycemia:

  • Staying active: Regular exercise is an effective way to manage blood sugar. Steady-state, cardio-type exercises tend to lower overall blood sugar levels better than high intensity interval training. Taking a long walk or bike ride can help the body use existing glucose.
  • Taking medications as directed: People with diabetes should always take medication and follow a doctor’s instructions closely. A doctor can adjust a prescription to suit a person’s ongoing needs.
  • Eating: A doctor or dietitian can help a person with diabetes develop an appropriate eating plan.
  • Managing stress: Taking steps to manage stress and any health conditions may be an effective way to reduce stress-related blood sugar spikes.

Hyperglycemia is a key sign of diabetes, which is a serious condition.

People with diabetes must monitor their blood sugar, stay within their target range, follow a dedicated eating plan, exercise regularly, and always take their medication.

A person with diabetes should report any abnormal symptoms to their doctor. Doing so can help them prevent hyperglycemia and receive early treatment in order to avoid long-term complications.

Q: What is the best diet for keeping blood sugar within a healthy range?

A: Many types of diet can benefit people with diabetes. Eating carbohydrates, for example, directly affects blood sugar, so doctors recommend a carb-controlled diet.

Ketogenic diets have become popular because they can lead to rapid weight loss. However, they may have some negative health effects, so a person should talk with their doctor before beginning any extreme diet.

Moderation is the best advice, with about 45% of a person’s calories coming from low glycemic carbs such as legumes; whole grains such as stone-ground whole wheat bread, oatmeal, or barley; and non-starchy vegetables and fruits.

Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.