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High blood sugar (hyperglycemia) and diabetic ketoacidosis

Scientific support: Andreas Vosseler M.A.

High blood sugar (or hyperglycemia) causes the blood sugar level to rise above 250 mg/dl (13.9 mmol/l). Very high levels indicate an acute emergency. The result may be a life-threatening diabetic coma.

Symptoms of hyperglycemia can include fatigue, increased thirst, increased urination, and nausea. The primary cause of high blood sugar levels is a lack of insulin.

Hyperglycemia occurs in people with diabetes. A dangerous situation is diabetic ketoacidosis, which is associated with sweet smelling breath, labored breathing, and nausea. It can occur primarily in type 1 diabetes. In type 2 diabetes, ketoacidosis occurs less frequently. Instead, hyperosmolar hyperglycemic syndrome may develop, which is also an acute, life-threatening emergency.

As a rule, people with diabetes can compensate for high blood sugar levels themselves. Diabetes professionals often provide persons who inject insulin with a correction regimen. This regimen shows the blood sugar levels at which how much corrective insulin should be injected.

Note: Do not correct with insulin too soon after a meal. This carries the risk of hypoglycemia because the insulin injected at mealtime is still working in the body. Ask your diabetes team at what point after a meal elevated blood sugar levels may be counteracted with insulin.

1. Symptoms: How do you recognize high blood sugar levels?

The blood sugar level at which the first signs of hyperglycemia appear varies from individual to individual. Common symptoms of high blood sugar levels are:

  • Increased thirst
  • Increased urination
  • Dry mouth
  • Fatigue
  • Visual impairment
  • Nausea and vomiting
  • Stomach pain
  • Loss of appetite
  • Sweet smelling breath
  • Labored breathing (Kussmaul breathing)
  • Cramps
  • Changes in consciousness

Labored breathing and sweet smelling breath may be symptoms of diabetic ketoacidosis. This is a dangerous situation that requires immediate action.

Good to know:

You are not sure if it is hyperglycemia or hypoglycemia? Watch our video on acute emergencies in diabetes.

(This video is available with English subtitles.)

2. What are the causes of high blood sugar levels?

Various situations can lead to elevated blood sugar levels. The causes can partly be attributed to the therapy technique. For example, if the infusion set of an insulin pump has not been changed for a long time and the insulin no longer works properly. Diabetes management may also play a role: For example, if the carbohydrate content of a meal was underestimated and the dose of insulin that was injected was too low, or if medication or insulin was not administered. In addition, blood sugar can rise during stress or illness because insulin demand is increased. Altered injection sites can also contribute to elevated blood sugar levels.


The following is a list of possible causes of high blood sugar levels:

  • Diabetes has not yet been diagnosed (new manifestation)
  • Patients forgot to inject insulin or the carbohydrate content of a meal was underestimated
  • Increased insulin requirement due to an infection or stress
  • The insulin is no longer effective enough (for example, during a heatwave)
  • The insulin pen, needle, pump or infusion set is defective
  • Injection sites have been changed (lipohypertrophies)
  • Medications that reduce insulin sensitivity (for example, glucocorticoids) or cause a sharp increase in blood sugar levels

3. How can high blood sugar levels be prevented?

Severe hyperglycemia as well as hypoglycemia can be prevented by certain measures. For example, you should always carry an “emergency set” with you. This “emergency set” contains all the of the devices you need for diabetes therapy, such as dextrose, insulin pen, an additional insulin ampoule and batteries for the insulin pump. It is also useful to inform your environment about the disease. This will provide for understanding in case you need a break due to high or low blood sugar levels. If the class or work team is aware of potential metabolic imbalances, severe emergencies can be avoided.

4. First aid protocol for high blood sugar levels

5. What is diabetic ketoacidosis?

Diabetic ketoacidosis can result in blood sugar levels well above 250 mg/dl (13.9 mmol/l). It is characterized by a severe lack of insulin and requires quick action. Ketoacidosis mainly affects people with type 1 diabetes, because their pancreas produces very little or no insulin. However, diabetic ketoacidosis can also occur in people with type 2 diabetes.

What happens during ketoacidosis?

Insulin is a hormone that is essential for life. It ensures that sugar (glucose) is absorbed from the blood into the body cells to be used for energy.

If there is too little insulin in the blood, no sugar can enter the cells and the blood sugar level rises. In order to meet energy requirements in a different way, the body increasingly breaks down fat reserves. This process produces acidic ketone bodies. These build up in the blood and can lead to hyperacidification, a condition known as acidosis.

Some of the ketone bodies are excreted via the urine and exhaled through the breath, giving it a sweetish smell. The enormous elevation in blood sugar results in an increased urge to urinate. This causes a high loss of fluid and electrolytes. Dehydration and circulatory failure are a real threat. This is why the primary treatment for patients with diabetic ketoacidosis is a large amount of fluid intake. Without initiating countermeasures and appropriate therapy, ketoacidosis will lead to diabetic coma, which is life threatening.

What are the symptoms of ketoacidosis?

Diabetic ketoacidosis is usually accompanied by very high blood sugar levels exceeding 250 mg/dl (13.9 mmol/l). However, a high blood sugar level does not automatically mean that ketoacidosis is present.

In addition to the typical signs of hyperglycemia (increased thirst, increased urination, dry mouth), there are symptoms that indicate diabetic ketoacidosis:

  • Stomach pain, nausea and vomiting
  • Sweet smelling breath
  • Labored breathing (Kussmaul breathing)
  • Changes in consciousness

How to recognize ketoacidosis?

If people with type 1 diabetes notice any of the above symptoms, they should immediately test their blood sugar levels. If the value is above 250 mg/dl (13.9 mmol/l), then a ketone body test is needed. Ketones can be measured in urine or blood. Urine test strips or blood ketone test strips can be prescribed by the diabetes team. Some blood sugar measurement devices can also measure ketones in the blood using special test strips.

Testing ketones in blood

Testing ketones in urine

The measurement is performed like a blood sugar measurement.

  1. Get materials ready
  2. Wash and dry hands
  3. Insert the test strip into the measuring device
  4. Puncture the finger laterally with a lancing device
  5. Press gently until blood appears
  6. Aspirate the blood with the test strip
  7. The measurement result is displayed



The results depend on the analyzer and the analysis method. Therefore, contact the respective company to find out which values are to be classified and how. The following values will help you:


Normal: 0.0 to below 0.6 mmol/l

Slightly increased: 0.6 to 1.5 mmol/l

Elevated: above 1.5 mmol/l

  1. Collect urine in a container
  2. Briefly immerse the test field of the test strip in the urine
  3. After 15 seconds (depending on the manufacturer, other times are also possible), compare the color with the test strip packaging



Depending on the amount of ketone bodies in the urine, the test strip changes to between a light to dark color.

The darker the color, the more ketone bodies are in the blood.


Low (+/- to +)

Medium (++)

High (+++ or ++++)

Good to know:

Blood sugar levels should not be reduced too quickly in ketoacidosis to prevent adverse effects (e.g., cerebral edema).

Acting appropriately in the event of ketoacidosis

If the result of the ketone body test comes back positive, countermeasures must be initiated rapidly. In order to be able to act appropriately in an emergency, people with type 1 diabetes should have talked with their doctor beforehand.

In the early stages of diabetic ketoacidosis, trained patients are generally able help themselves. It is crucial to drink enough fluids and inject fast-acting insulin. In addition, blood sugar levels should be tested at short intervals (usually every 2 hours) and physical exertion avoided. If neither values nor symptoms improve within a few hours or if severe symptoms are already present (such as vomiting, stomach pain, drowsiness), a doctor should be called immediately. Medical help should also always be sought in the event of severe malaise or uncertainty regarding treatment.

What are the causes of diabetic ketoacidosis?

Diabetic ketoacidosis can develop for a variety of reasons. In the event of ketoacidosis, there is no or almost no insulin available in the body.

Type 1 diabetes: Ketoacidosis develops primarily in type 1 diabetes when hyperglycemia is not recognized and treated over a long period of time, resulting in a massive lack of insulin.

Because the symptoms of type 1 diabetes are often unknown, a new manifestation often results in dangerous ketoacidosis. However, diabetic ketoacidosis can also develop in existing type 1 diabetes due to the following causes:

  • Severe infections
  • Acute cardiovascular episodes
  • The amount of insulin that was injected was insufficient or patients forgot to inject insulin
  • Severe lack of insulin due to technical problems


Type 2 diabetes: In type 2 diabetes, diabetic ketoacidosis is rare. Causes can be:

  • Severe infections
  • Heavy alcohol consumption with and without metformin therapy
  • Severe lack of insulin in prolonged type 2 diabetes


A reason for a lack of insulin can also be, for example, a defect in the catheter of an insulin pump or ineffective insulin. Other causes are listed under “What are the causes of high blood sugar levels?”.

Diabetes Emergency Card

A Diabetes Emergency Card informs physicians and first responders in an emergency about the existing diabetes and medications taken.

Download the “Diabetes Emergency Card”

6. Hyperosmolar hyperglycemic syndrome (HHS) in type 2 diabetes

The blood sugar levels of patients with type 2 diabetes can also spike when there is not enough insulin available or it is not effective. However, since their pancreas generally releases at least small amounts of insulin, there is not a massive buildup of ketone bodies as in ketoacidosis. The abbreviation “HHS” stands for hyperosmolar hyperglycemic syndrome.

This type of metabolic imbalance is very dangerous. Those affected can have extremely high blood sugar levels exceeding 600 mg/dl (33.3 mmol/l) or even 1000 mg/dl (55.5 mmol/l). They also suffer from severe dehydration.


Hyperosmolar hyperglycemic syndrome can be triggered by the following situations:

  • Infections
  • Acute cardiovascular events
  • Vomiting
  • Severe diarrhea
  • Kidney diseases
  • Large quantities of sugar-containing drinks (for example, fruit juices or lemonades)
  • Medications such as diuretics, certain psychoactive drugs, and glucocorticoids


Typical symptoms are:

  • Increased thirst
  • Frequent urination
  • Visual impairment
  • Cramps in the calf
  • Fatigue
  • Tachycardia
  • Low blood pressure
  • Dizziness
  • Feeling of faintness
  • Cramps


Without the initiation of countermeasures, there is a risk of hyperosmolar coma. Older people with type 2 diabetes are especially at risk. When in doubt, affected persons should immediately call the emergency services (112).

More information on hypoglycemia and hyperglycemia in diabetes


American Diabetes Association: Diabetes & DKA (Ketoacidosis). (Letzter Abruf: 05.04.2023)
Bundesärztekammer et al.: Nationale Versorgungsleitlinie Therapie des Typ-2-Diabetes. Langfassung. 1. Auflage. Version 4. 2014 (Gültigkeit abgelaufen, in Überarbeitung)
Bundesärztekammer et al.: Nationale Versorgungsleitlinie Typ-2-Diabetes. Teilpublikation der Langfassung. 2. Auflage. Version 1. 2021
Deutsche Diabetes Gesellschaft: S3-Leitlinie Therapie des Typ-1-Diabetes. 2. Auflage. 2018
Häring, H.-U. et al. (2021): Diabetologie in Klinik und Praxis. 7. Auflage. Georg Thieme Verlag KG, ISBN: 9783132428911
Hien, P. et al. (2013): Diabetes Handbuch. 7. Auflage. Springer-Verlag, Heidelberg, ISBN: 978-3-642-34944-7
Kitabchi, A. E. et al.: Hyperglycemic Crises in Adult Patients With Diabetes. In: Diabetes Care, 2009, 32: 1335-1343
Beipackzettel: Ketostix® Teststreifen. Bayer HealthCare
Nyenwe, E. A. et al.: The evolution of diabetic ketoacidosis: An update of its etiology, pathogenesis and management. In: Metabolism, 2016, 65: 507-521
As of: 05.04.2023