Hyperglycemia refers to high levels of sugar, or glucose, in the blood. It occurs when the body does not produce or use enough insulin. This hormone helps cells absorb glucose for use as energy.

High blood sugar may indicate diabetes or prediabetes. If a person with diabetes does not manage the sugar levels in their blood, they can develop a severe complication called diabetic ketoacidosis (DKA).

If a person does not get treatment for ketoacidosis, they can fall into a diabetic coma, which is a dangerous complication of diabetes.

This article looks at how to recognize hyperglycemia, how to treat it, and possible causes and complications.

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There are different diagnostic thresholds for hyperglycemia. Some define hyperglycemia as a blood glucose level of more than 125 milligrams per deciliter (mg/dl) when fasting and 180 mg/dl after a meal. Meanwhile, 2022 guidelines from the American Diabetes Association recommend defining hyperglycemia by the percentage of time a person spends above the 180 mg/dl threshold.

Hyperglycemia symptoms may include:

Even if a person has a blood glucose level above 180 mg/dl, symptoms may not occur immediately or at all. Underlying health conditions and typical blood sugar levels can all affect the onset and severity of symptoms.

A person may have hyperglycemia but experience no noticeable symptoms for years. Symptoms may also worsen the longer blood sugar levels remain high.

People with diabetes should self-monitor regularly to catch glucose levels before they reach the stage where they cause symptoms.

A person with diabetes can take steps to reduce, prevent, and treat blood glucose spikes. These steps include:

  • Blood sugar monitoring: It is essential for a person with diabetes to track their blood sugar levels as recommended by their doctor. Blood glucose tests help catch hyperglycemia before it becomes a problem.
  • Exercise: Physical activity uses excess glucose in the blood. However, people should avoid exercise if they have severe hyperglycemia and find ketones in their urine. Exercise breaks down more fats and might speed up ketoacidosis.
  • Diet changes: Controlling portions during mealtimes and snacking less — along with monitoring carbohydrate quality and quantity — helps keep the amount of glucose at a level the body can handle.
  • Medication alterations: A doctor may recommend changing the timings or types of medication and insulin a person takes if their blood sugar levels remain elevated.
  • Stress management: High stress levels can impact hormones and blood sugar levels. It is important for people with diabetes to find ways to manage stress, such as prioritizing sleep and trying relaxation techniques, like meditation.

Managing diabetes is an ongoing and often lifelong endeavor. Typically, a doctor can look at a person’s self-monitored results, identify issues, and help individuals find ways to prevent severe spikes.

Medical ID

A person with diabetes and especially hyperglycemia should consider wearing a necklace or bracelet that provides information about their condition, as it might impact the administration of other treatments.

A medical ID contains essential information, such as whether the individual:

  • has diabetes
  • has any allergies
  • needs to take insulin

The information in a medical ID can be life-saving in situations where an individual cannot speak for themselves, such as after a vehicle accident or during severe DKA.

Hyperglycemia usually occurs in people with prediabetes or diabetes. The causes of hyperglycemia in people with diabetes include:

  • eating more than the body requires for its energy needs
  • not getting enough physical activity
  • experiencing stress in work, life, and relationships, which can release hormones that keep glucose at high levels in the blood
  • having an illness, such as the flu, which might lead to stress that causes a spike in blood sugar
  • missing a dose of diabetes medication, such as insulin

Hyperglycemia in people who do not have diabetes is known as nondiabetic hyperglycemia. It may occur in people who are critically ill or injured when the body responds to extreme stress with hormonal changes that affect blood sugar levels.

Additionally, hyperglycemia can occur in people with certain health conditions, such as pancreatic and hormonal disorders. It can also be a side effect of certain drugs. This is known as secondary diabetes.

Dawn phenomenon

A common cause of hyperglycemia in people with diabetes is the dawn phenomenon.

This condition occurs in the early morning when certain hormones, such as epinephrine, glucagon, and cortisol, cause the liver to release glucose into the blood.

This phenomenon typically occurs around 8 to 10 hours after an individual with diabetes sleeps.

However, not all cases of high blood sugar levels in the morning result from the dawn phenomenon. Hyperglycemia can also occur as a result of:

  • eating sugary or high carbohydrate snacks before bed
  • taking an incorrect dose of medication
  • not taking enough insulin
  • the body correcting low blood sugar during the night, known as the Somogyi effect

Waking up during the night and testing blood sugar can effectively determine whether these peaks result from the dawn phenomenon or other causes.

Hyperglycemia is high blood glucose levels, while hypoglycemia is low blood glucose levels. In people with diabetes, low blood sugar levels requiring treatment are usually less than 70 mg/dl. This recommendation can vary from person to person.

Very low blood glucose levels can be harmful and require immediate treatment. Some symptoms of excessively low blood glucose include:

If blood glucose levels become severely low, the brain can stop functioning properly. This can cause symptoms such as:

  • confusion
  • blurred vision
  • slurred speech
  • seizures
  • loss of consciousness or coma
  • in rare cases, death

A person can only know if they have hypoglycemia by testing their blood sugar levels. If that is not possible, the American Diabetes Association suggests that a person take steps to treat hypoglycemia as recommended by their doctor or seek medical attention if symptoms are severe.

Many people experience an increase in blood sugar levels after eating an unusually large meal that is high in carbohydrates. People who experience consistent hyperglycemia may have problems with low or inefficiently used insulin caused by diabetes.

Insulin is a hormone produced in the pancreas that allows cells to use glucose for generating energy and functioning normally. When insulin is low or inefficient, diabetes may develop.

There are two types of diabetes: Type I diabetes occurs when the body does not produce insulin. Type 2 diabetes occurs when the body does not use insulin effectively. As a result, glucose remains in the blood and circulates in the body.

Over time the body may also stop producing adequate levels of insulin in people with type 2 diabetes. However, this does not happen in all cases of type 2 diabetes.

People who are overweight or have obesity and do not get enough physical activity may have continuously high amounts of sugar in the blood. This makes the body resistant to insulin, meaning glucose cannot enter the cells and builds up in the blood. Eventually, this can lead to type 2 diabetes.

The complications of diabetes are often the effects of prolonged hyperglycemia.

When blood sugar levels are consistently high because of diabetes, a range of health problems might develop, including the following:

Skin complications

People with prolonged hyperglycemia might be more prone to bacterial and fungal infections, such as boils, jock itch, athlete’s foot, and ringworm.

Other diabetic skin conditions can cause spots and lesions to develop, which may cause pain and itching. These include:

  • diabetic dermopathy, which can lead to oval or circular, scaly, light brown patches on the legs
  • acanthosis nigricans, which causes raised brown areas on the neck, groin, and armpits
  • necrobiosis lipoidica diabeticorum, which is a rare complication that causes a sometimes painful, scar-like lesion with a violet edge
  • diabetic blisters, which most often develop on the extremities and are painless
  • eruptive xanthomatosis, a condition that causes yellow, pea-sized lumps on the skin that have a red ring around the base
  • digital sclerosis, which causes thick skin with a waxy texture to develop on the back of the hand
  • disseminated granuloma annulare, which causes raised, ring-shaped or arc-shaped patches on the skin

Read more about diabetic skin conditions.

Nerve damage

Consistently high blood sugar can damage the nerves in several ways:

  • Peripheral neuropathy: This is nerve damage in the feet and hands, leading to numbness, tingling, or weakness. People may not be aware of when they injure their feet and should check them daily to avoid infected wounds.
  • Autonomic neuropathy: This affects automatic processes in the body, such as bladder control, sexual function, and digestion.
  • Other types of neuropathy: Persistently raised blood sugar may lead to hand, head, torso, thigh, hips, buttocks, or leg neuropathy.

Read more about the types of neuropathy.

Eye complications

People with diabetes with consistently high blood sugar levels might experience diabetic retinopathy. This causes damage to blood vessels in the back of the eye, leading to vision loss and possible blindness.

Having diabetes significantly increases the risk of both glaucoma and cataracts.

Diabetic ketoacidosis

DKA is a life threatening condition that occurs if a person does not treat severe hyperglycemia. It is most common in people with type 1 diabetes.

If a person with diabetes does not take steps to control their blood sugar levels, cells become less sensitive to insulin. When there is insufficient insulin in the body or the cells do not respond, and glucose cannot access the cells, the body uses fats for energy instead. The body produces ketones by breaking down fats.

The body cannot handle a high level of ketones. While it can get rid of some in the urine, ketones may eventually build up, causing the blood to become too acidic. This can lead to complications, such as DKA.

DKA increases levels of acid in the body. Without treatment, it might lead to a diabetic coma. Some symptoms of DKA include:

  • breathlessness
  • fruity-smelling breath
  • vomiting and nausea
  • parched mouth
  • weight loss

Anyone with diabetes who suspects DKA should speak with their doctor about their symptoms and when to seek emergency care.

Learn more about diabetic ketoacidosis.

Hyperglycemia is high blood glucose that can occur in people with diabetes due to several conditions, including insufficient or ineffective insulin, diabetes medications, or diet and lifestyle changes. People without diabetes may also experience hyperglycemia.

Hormone spikes due to stress and the dawn phenomenon can also lead to periods of hyperglycemia.

Symptoms include frequent urination, intense thirst, and high blood sugar readings during self-monitoring. If a person does not address high blood glucose, they might develop ketoacidosis, a dangerous buildup of waste products that can lead to diabetic coma.

Treatment may include adjustments in diabetes medication, exercise, and eating less during meals. Wearing a medical ID is essential for people with diabetes, as this can impact other treatments.