What happens when your blood sugar is too high symptoms

Non-urgent advice: Speak to your care team or GP surgery if:

• you've tried to lower your blood sugar but your blood sugar level is still high or you still have symptoms
• you have symptoms of high blood sugar and you have not been diagnosed with diabetes

Urgent advice: Call your care team immediately or get help from NHS 111 if:

You think you have high blood sugar and:

• you're feeling sick, being sick or have stomach pain
• you're breathing more quickly than usual or your heart is beating faster than usual
• you feel drowsy or are struggling to stay awake
• your breath has a fruity smell (like pear drop sweets)
• you feel confused or have difficulty concentrating
• you have a high level of ketones in your blood or pee

These could be signs you're becoming seriously unwell.

You can call 111 or get help from 111 online.

Page last reviewed: 26 May 2022
Next review due: 26 May 2025

Have you ever felt like no matter how much water or juice you drink, it just isn’t enough? Does it seem like you spend more time running to the restroom than not? Are you frequently tired? If you answered yes to any of these questions, you may have high blood sugar.

High blood sugar, or hyperglycemia, primarily affects people who have diabetes. It occurs when your body doesn’t produce enough insulin. It can also happen when your body is unable to absorb insulin properly or develops a resistance to insulin entirely.

Hyperglycemia can also affect people who don’t have diabetes. Your blood sugar levels can spike when you’re ill or under stress. This occurs when the hormones that your body produces to fight off illness raise your blood sugar.

If your blood sugar levels are consistently high and left untreated, it can lead to serious complications. These complications can involve problems with your vision, nerves, and cardiovascular system.

You generally won’t experience any symptoms until your blood sugar levels are significantly elevated. These symptoms can develop over time, so you may not realize that something is wrong at first.

Early symptoms can include:

• increased urinary frequency
• increased thirst
• blurred vision
• headaches
• fatigue

The longer the condition remains untreated, the more serious symptoms can become. If left untreated, toxic acids can build up in your blood or urine.

More serious signs and symptoms include:

• vomiting
• nausea
• dry mouth
• shortness of breath
• abdominal pain

Your diet may cause you to have high blood sugar levels, particularly if you have diabetes. Carbohydrate-heavy foods such as breads, rice, and pasta can raise your blood sugar. Your body breaks these foods down into sugar molecules during digestion. One of these molecules is glucose, an energy source for your body.

After you eat, glucose is absorbed into your bloodstream. The glucose can’t be absorbed without the help of the hormone insulin. If your body is unable to produce enough insulin or is resistant to its effects, glucose can build up in your bloodstream and cause hyperglycemia.

Hyperglycemia can also be triggered by a change in your hormone levels. This commonly happens when you’re under a lot of stress or when you’re feeling ill.

Hyperglycemia can affect people regardless of whether they have diabetes. You may be at risk of hyperglycemia if you:

• lead a sedentary or inactive lifestyle
• have a chronic or severe illness
• are under emotional distress
• use certain medications, such as steroids
• have had a recent surgery

If you have diabetes, your blood sugar levels may spike if you:

• don’t follow your diabetes eating plan
• don’t use your insulin correctly
• don’t take your medications correctly

Learn more: Hyperglycemia and type 2 diabetes »

If you have diabetes and notice a sudden change in your blood sugar levels during your home monitoring, you should alert your doctor of your symptoms. The increase in blood sugar may affect your treatment plan.

Regardless of whether you have diabetes, if you begin experiencing any symptoms of hyperglycemia, you should speak to your doctor. Before going to your appointment, you should note what symptoms you’re experiencing. You should also consider these questions:

• Has your diet changed?
• Have you had enough water to drink?
• Are you under a lot of stress?
• Were you just in the hospital for surgery?
• Were you involved in an accident?

Once at your doctor’s appointment, your doctor will discuss all of your concerns. They’ll perform a brief physical exam and discuss your family history. Your doctor will also discuss your target blood sugar level.

If you’re age 59 or younger, a safe blood sugar range is generally between 80 and 120 milligrams per deciliter (mg/dL). This is also the projected range for people who don’t have any underlying medical conditions.

People who are age 60 or older and those who have other medical conditions or concerns may have levels between 100 and 140 mg/dL.

Your doctor may conduct an A1C test to determine what your average blood sugar level has been in recent months. This is done by measuring the amount of blood sugar attached to the oxygen-carrying protein hemoglobin in your red blood cells.

Depending on your results, your doctor may recommend routine home blood sugar monitoring. This is done with a blood sugar meter.

Your doctor may recommend a low-impact exercise program as your first line of defense. If you’re already following a fitness plan, they may recommend that you increase your overall level of activity.

Your doctor may also suggest that you reduce glucose-rich food intake. It’s important to maintain a balanced diet and stick to healthy food portions. If you aren’t sure where to begin, your doctor can refer you to a dietician or nutritionist who can help you establish a diet plan.

If these changes don’t help lower your high blood sugar, your doctor may prescribe medication. If you have diabetes, your doctor may prescribe oral medications or change the amount or type of insulin you’ve already been prescribed.

Your doctor will provide you with clear steps to follow aimed at lowering your blood sugar levels. It’s important that you take their recommendations to heart and make any necessary lifestyle changes to improve your health. If left untreated, hyperglycemia can lead to serious, and sometimes life-threatening, complications.

Your doctor may recommend that you buy a blood glucose meter to use at home. This is a simple and effective way to monitor your blood sugar and act quickly if your levels have spiked to an unsafe level. Being aware of your levels can empower you to take charge of your condition and live a healthy lifestyle.

By being aware of your numbers, keeping hydrated, and staying fit, you can more easily manage your blood sugar.

Keep reading: How to lower blood glucose levels »