Woman drinking a glass of water
As more water is absorbed from the blood into the urine, a diabetic with high blood sugar may feel very thirsty with a dry mouth and throat, even if they are drinking a healthy amount.

Symptoms of High Blood Sugar Levels in Diabetics

If you are diabetic, high blood sugar (also known as hyperglycemia) is a very common issue. It can occur after overindulging in carbohydrates, exercising less than usual, or missing a dose of your medication. High blood sugar can also be a result of stress, illness or over-treating a hypoglycemic episode.

Occasional, temporary rises in blood sugar are not a major cause for concern. However, when your blood sugar remains high for a long period, it can increase the risk of complications such as eye, nerve, blood vessel or organ damage. It can also make you more susceptible to heart disease and strokes.

Perhaps of even greater concern are the short-term effects of extremely high blood sugar levels. These can lead to diabetic emergencies and if left untreated, could even result in death.

So, how do you know when your blood sugar levels are too high? Here are some of the most common symptoms of high blood sugar levels in diabetics and how to prevent them.

Symptoms of High Blood Sugar

One of the best ways to avoid hyperglycemia becoming a medical emergency is to know the early symptoms and what to do when they occur. Some of the most common high blood sugar symptoms in diabetics include:


Humans need a certain amount of sugar in order to provide energy for their physiological processes. Therefore, you might think that having high blood sugar levels would make you more energetic.

However, diabetics cannot produce enough insulin to convert this sugar to energy, or their cells are resistant to insulin’s effects. Therefore, diabetics with high blood sugar can feel tired, drowsy and fatigued.

Frequent Urination

The excess sugar in a diabetic’s blood will eventually travel to the kidneys, increasing the concentration of glucose in the urine. As the kidneys attempt to regain balance, more water is absorbed from the blood and urination becomes more frequent.

Excessive Thirst

As more water is absorbed from the blood into the urine, a diabetic with high blood sugar may feel very thirsty with a dry mouth and throat, even if they are drinking a healthy amount.


In the short term, nausea can be a result of high blood sugar upsetting the body’s normal metabolism and making the digestive system confused.

In the long term, high blood sugar can damage nerves along the digestive tract, making it difficult for food to pass through the stomach and intestines normally. This can cause nausea, and in severe cases vomiting.

Blurred Vision

Short-term visual disturbances can be due to high blood sugar causing the lens of the eye to swell. The role of the lens is to focus light onto the back of the eye, just like the lens of a camera. When it becomes swollen, light gets distorted causing blurred vision.

Blurred vision can also be a sign of diabetic retinopathy, a condition where high blood sugar damages the blood vessels supplying the retina. The retina is responsible for detecting light and helping us to see clearly. This is why diabetics should have regular eye tests.

Weight Loss

If blood sugar is too high for long periods, the body begins to burn fat and muscle to produce energy. This can lead to weight loss, even if your diet and exercise regime have not changed.

Diabetic Ketoacidosis

Diabetic ketoacidosis (DKA) is a serious condition that develops when high blood sugar causes ketones to build up in the body. It is most common in type I diabetes, but may affect type II diabetics too.

The symptoms of DKA are very similar to those of high blood sugar. They include:

  • Frequent urination
  • Thirst
  • Vomiting
  • Abdominal pain
  • Drowsiness
  • Confusion
  • Fruity-smelling breath
  • Loss of consciousness

DKA usually develops very quickly, over the course of 24 hours or less. It is a medical emergency and anyone experiencing these symptoms should call 911 or visit the emergency room immediately.

You May Also Like

Hyperosmolar Hyperglycemic Non-Ketotic Syndrome

Hyperosmolar hyperglycemic non-ketotic syndrome (HHNS) is another diabetic emergency caused by high blood sugar. It is more common in type II diabetics and usually occurs during illness as a result of dehydration.

The symptoms of HHNS include:

  • Frequent urination
  • Thirst
  • Nausea
  • Dry skin
  • Drowsiness
  • Confusion
  • Loss of consciousness

Like DKA, HHNS requires immediate treatment to prevent a diabetic coma, brain damage or even death.

It is a good idea to talk to your physician in advance about how you will manage your diabetes if you become sick. They will help you to formulate a plan to prevent HHNS if you are unable to drink enough fluids or take your medication normally.

How to Prevent High Blood Sugar Levels in Diabetics

Managing your blood sugar levels is one of the most important things you can do as a diabetic. Fortunately, this is easy to do by taking your medication correctly and making some simple lifestyle changes.

Eating too many carbohydrates is one of the main culprits of high blood sugar. As well as avoiding sweets, soda, desserts and baked goods, watch out for starchy foods such as pasta, potatoes and grains. Talk to your health care provider about how many carbs you should be eating with each meal, and which foods you should avoid.

As well as paying attention to what you eat, you should also be mindful of your drinking habits. Stay well hydrated at all times, but stick with sugar-free beverages such as water or unsweetened tea. Alcohol should only be drunk in moderation.

Regular exercise is another important way to keep your blood sugar levels under control. However, you should avoid exercising if you have the signs of DKA as physical activity can make this condition worse.

Finally, check your blood glucose levels daily and keep an accurate record of your results. Be sure to get your HbA1c readings done regularly too, as these will help you to monitor your blood sugar over time.

If your blood sugar levels are consistently high, you may need to adjust your medication or dosage. Make an appointment with your physician to discuss this as soon as possible.