If a person has high blood sugar, or hyperglycemia, they may feel unusually thirsty and urinate more than usual. However, high blood sugar levels can cause a range of symptoms.

The liver and muscles produce some blood sugar, but most of it comes from food and drinks containing carbohydrates.

The body needs insulin to keep blood sugar levels within a normal range. Insulin is a hormone that directs the body’s cells to take up glucose and store it.

If there is not enough insulin or it does not work properly, blood sugar builds up. High blood sugar levels can cause health concerns.

This article explores what hyperglycemia feels like, why it occurs, and the signs of high blood sugar. Read on to find out more.

Hyperglycemia, or high blood sugar, is an issue that can affect people with type 1 or type 2 diabetes.

There are two main types, including:

  • Fasting hyperglycemia: It occurs when a person with diabetes has blood sugar levels above 130 milligrams per deciliter (mg/dL) after not eating or drinking for 8 hours or more.
  • Postprandial hyperglycemia: It occurs when someone with diabetes has blood sugar levels of 180 mg/dL or higher 1–2 hours after eating.

Having high blood sugar levels frequently or for prolonged periods can cause several adverse symptoms and increase the risk of severe complications over time.

Blood sugar serves as fuel for the body’s organs and functions.

However, having high blood sugar does not provide a boost in energy.

In fact, the opposite often happens because the body’s cells cannot access the blood sugar for energy.

According to the American Diabetes Association, symptoms of hyperglycemia include:

  • high blood sugar levels
  • high levels of sugar in the urine
  • frequent urination
  • increased thirst

People can experience high blood sugar levels in the morning, especially if they have diabetes.

Explore more about high blood sugar levels.

Testing kits for levels of blood sugar and ketone levels are available for purchase online for home use.

However, anyone who thinks they have diabetes should speak with a doctor first.

How does high blood sugar affect the body?

High blood sugar can lead to several other symptoms and complications. They include:

  • Extreme fatigue: When the body doesn’t produce enough insulin, sugar can stay in the blood instead of going to cells where it can be used for energy. This can cause extreme tiredness. Fatigue can also be caused by dehydration, which can result from frequent urination.
  • Blurred vision: According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), high blood sugar can cause swelling in the part of the eye that helps focus. This can lead to temporary blurry vision.
  • Excessive thirst: High blood sugar in the kidneys and urine can also lead to increased thirst, even if someone drinks liquids.
  • Slow healing cuts and sores: High blood sugar can affect circulation, which can delay the healing of cuts, bruises, scrapes, and other wounds.
  • Unexplained weight loss: High blood sugar can cause sudden or unexplained weight loss. This occurs because the body’s cells are not getting the glucose they need, so the body burns muscle and fat for energy instead.
  • Urinating often: High blood sugar goes into the kidneys and urine. This attracts more water, causing frequent urination.
  • Numbness and tingling: High blood sugar can also cause numbness, burning, or tingling in the hands, legs, and feet. This is due to diabetic neuropathy, a complication of diabetes that often occurs after many years of high blood sugar levels.

Long-term complications

Over time, high blood sugar can harm the body’s organs and systems. Damage to the blood vessels can lead to complications, including:

When a person has high blood sugar, they may:

  • have a headache and other aches and pains
  • find it hard to concentrate
  • be very thirsty or hungry
  • feel drowsy or tired
  • have blurred vision
  • feel their mouth is dry
  • experience bloating
  • need to urinate often
  • notice that wounds take a long time to heal

High blood sugar and low insulin can lead to a rise in ketones and possibly diabetic ketoacidosis, a serious complication that needs urgent medical attention.

If diabetic ketoacidosis occurs, an individual may experience:

In addition, the person’s blood sugar levels may be over 240 mg/dL.

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Gestational diabetes can occur during pregnancy. Image credit: Halfpoint/Shutterstock

Several types of diabetes can lead to high blood sugar.

In type 1 diabetes, the immune system attacks the cells in the pancreas that produce insulin. As a result, the body lacks insulin, and blood sugar levels rise.

People with type 1 diabetes must take insulin through a needle, pen, or insulin pump to keep their blood sugar levels within the target range.

Only about 5% of all those with diabetes have type 1, according to the American Diabetes Association.

In type 2 diabetes, the body does produce insulin but cannot use it properly. The pancreas tries to make more of the hormone but often cannot make enough to keep blood sugar levels steady. This is known as insulin resistance.

People with type 2 diabetes may need insulin, pills, dietary changes, or exercise to help manage blood sugar levels.

Gestational diabetes can occur when insulin resistance and high blood sugar levels appear during pregnancy. People should monitor this during pregnancy, as it can lead to complications for a pregnant person and their baby. Gestational diabetes usually goes away after delivery.

There may also be a link between diabetes and cystic fibrosis, a genetic condition that affects the lungs, pancreas, and digestive tract.

Additionally, people who take beta-blockers and certain steroids may also experience high blood sugar.

Risk factors for high blood sugar

Doctors do not know what exactly causes diabetes. However, some factors may increase the risk.

Type 1 diabetes

Researchers believe certain genetic or environmental factors may make people more likely to get type 1 diabetes.

The NIDDK notes certain genes play a role and that other factors — such as viruses and infections — may have an impact.

The Juvenile Diabetes Research Foundation states that there is nothing a person can do to prevent type 1 diabetes. Eating, exercising, or other lifestyle choices will not change the outcome.

Type 1 diabetes usually begins during childhood or early adulthood, but it can happen at any age.

Type 2 diabetes

The following risk factors may increase the risk of developing type 2 diabetes:

  • having certain genes
  • having overweight or obesity
  • being physically inactive
  • having a parent or sibling with type 2 diabetes
  • having African American, Alaska Native, American Indian, Asian American, Hispanic, or Pacific Islander ethnicity
  • being over 45 years old
  • receiving treatment for high blood pressure or having blood pressure above 130/80 millimeters of mercury
  • having low levels of high density lipoprotein (good) cholesterol or high levels of triglycerides
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Regular blood sugar testing can help people with diabetes keep their blood sugar levels within the target level. Image credit: ChooChin/Shutterstock

People who have high blood sugar should discuss their target levels with a doctor.

They may need regular testing to keep these within a healthy range. Each person is different, and levels can vary between individuals.

To find out their blood sugar levels, a person may need to fast for 8 hours, 2 hours after a meal, or at both times.

Some people may also take a glucose tolerance test, where they drink a sugary liquid and have a blood test after.

The American Diabetes Association recommends a premeal blood sugar level of 80–130 mg/dL. Around 1–2 hours after beginning a meal, their blood sugar should be less than 180 mg/dL.

Managing blood sugar levels

Many people with diabetes must check their blood sugar levels daily with a glucose meter. This device takes a drop of blood, usually from a finger, and displays the sugar level within a few seconds.

People with type 1 diabetes will need to take insulin as their doctor recommends, usually several times a day.

Those with type 2 diabetes or gestational diabetes may need to change their diet and exercise habits. They may also need to take oral medications or insulin.

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Monitoring your diet and exercise alongside blood sugar levels can help you maintain a healthy blood sugar level. Image credit: Fertnig/iStock

Various strategies can help prevent hyperglycemia.

People should:

  • Check their blood sugar levels as their doctor advises and take the proper amount of insulin if they have type 1 diabetes.
  • Speak with a doctor or dietitian about which foods to eat or avoid, how much to eat, and how often.
  • Take precautions to avoid infections through regular handwashing, as illness, such as a cold, can trigger an increase in blood sugar levels.
  • Plan their food intake and exercise to balance blood sugar levels.
  • Minimize stress through exercise, getting enough sleep, and stress-reducing activities such as meditation or yoga.

Low blood sugar, or hypoglycemia, can occur when a person:

  • has certain medical conditions
  • uses specific medications
  • does a lot of exercise
  • skips meals or eats too little

It can also be a side effect of diabetes medication. Taking too much insulin can result in low blood sugar levels.

Symptoms of low blood sugar may include:

  • feeling weak or shaky
  • sudden nervousness, anxiety, or irritability
  • sweating or chills
  • extreme hunger
  • confusion
  • fast heart rate, or palpitations

A person can treat hypoglycemia rapidly by drinking fruit juice or eating a glucose tablet, sugar lump, or candy.

Anyone who has frequent episodes of low blood sugar should speak with a doctor. A healthcare professional may recommend changing the type or dose of medication.

Anyone who experiences tiredness, increased thirst, frequent urination, or weight loss should consult a doctor, as these symptoms could indicate diabetes or another health concern.

A routine health check often involves blood sugar testing, even if the person has no symptoms.

The U.S. Preventive Services Task Force recommends screening for diabetes and prediabetes for adults ages 35–70 years who have overweight or obesity.

Those with a family history of diabetes or other risk factors may need earlier or more frequent tests.

The following are answers to commonly asked questions about high blood sugar.

How do you treat postprandial hyperglycemia?

In people with diabetes, a doctor may recommend taking certain medications before or after meals. They can also recommend dietary changes to prevent post-meal blood sugar spikes.

What is postprandial hypoglycemia?

Postprandial hypoglycemia is when a person’s blood sugar levels drop off after eating.

What is postprandial blood sugar level for diabetes?

Postprandial (post-meal) blood glucose for a person with diabetes is less than 180 mg/dL.

What are the signs and symptoms of hypoglycemia and hyperglycemia?

Hyperglycemia (high blood sugar) can cause frequent urination and increased thirst. Hypoglycemia (low blood sugar) can cause dizziness, shaking, and a rapid heartbeat.

When a person has diabetes, their health and well-being depend on managing their blood sugar levels properly.

To improve or maintain a good quality of life, an individual should:

  • consult a doctor regularly
  • take medications as a doctor prescribes
  • follow diet and exercise guidelines

These strategies can help a person with diabetes manage their blood sugar levels and may also slow the progression of the condition.

These individuals should also carry a medical ID with them, especially if they use insulin, as this can provide important information in case of an emergency.

Many medical IDs are now available with a compact USB drive containing a person’s full medical record.