Diabetic comas

What is a diabetic coma?

A diabetic coma is a serious medical emergency that can happen in people with diabetes. A coma can be life-threatening if not treated properly. It requires urgent medical attention.

Depending on the type of diabetes, and other factors, different types of diabetic coma can happen – See ‘Types of diabetic coma’.

Understanding diabetes

Diabetes is a serious disease that can affect the body in many ways. It is concerned with glucose and insulin.

Glucose is a type of sugar. It is used by the body’s cells as energy. You get glucose from the food you eat.

Insulin is a hormone that affects how your body manages glucose. It helps glucose get from your bloodstream into cells. You make insulin in your pancreas, which is a gland in your abdomen.

There are three different types of diabetes:
  • type 1 diabetes
  • type 2 diabetes
  • gestational diabetes.

In all three types, people with diabetes have trouble maintaining healthy levels of glucose in their blood.

The most common type of diabetes is type 2 diabetes. People with type 2 diabetes can make insulin, but the cells of the body are unable to use it properly. Type 2 diabetes is managed by a combination of diet, weight loss and medications called hypoglycaemics.

People with type 1 diabetes (also called ‘insulin dependent diabetes’) can’t make their own insulin. They need to take insulin every day, either as injections or using an insulin pump.

Gestational diabetes is a type of diabetes that can affect pregnant women. It usually goes away after the baby is born.

Types of diabetic coma

There are three main types of diabetic coma:

  1. diabetic ketoacidosis (DKA)
  2. hyperosmolar hyperglycaemic state (HHS)
  3. hypoglycaemic coma (hypoglycaemia).

Diabetic ketoacidosis

Diabetic ketoacidosis is a serious condition caused by a lack of insulin in the body. DKA usually affects people with type 1 diabetes. It may even be the first sign that they have diabetes.

Without insulin, the body’s cells can’t absorb glucose, and glucose levels in the blood begin to rise. The body’s cells begin to use fat as an energy source instead. This produces dangerous chemicals called ketones, which build up in the blood. This is called ketoacidosis.

The first signs are usually excessive thirst and frequent urination. Then comes dehydration, abdominal pain, vomiting, deep rapid breathing and a ‘sweet smelling’ breath. Left untreated, the person will become drowsy and may fall into a coma. This is a medical emergency and requires urgent medical attention.

Hyperosmolar hyperglycaemic state

Hyperosmolar hyperglycaemic state is a medical emergency that can happen in people with type 2 diabetes. HHS is similar to ketoacidosis, but the person affected doesn’t produce high levels of ketones.

Like DKA, HHS is treated using insulin and large amounts of fluids.

Hypoglycaemic coma

Hypoglycaemic coma happens when someone with diabetes gets an extremely low blood sugar level (hypoglycaemia) and there is not enough glucose for their brain to function normally. If this happens, they will become unconscious very quickly. They need a source of glucose urgently. All people with diabetes need to have an emergency plan ready to put into action if they become hypoglycaemic. This usually involves keeping a source of fast-acting glucose on hand in case they notice symptoms of hypoglycaemia, such as sweating and light-headedness.

If someone who has diabetes loses consciousness and you are unable to wake them, it is important that you do not put anything in their mouth, as they may choke. Instead, the condition is usually treated by injecting concentrated glucose, which normally leads to recovery within minutes.

Admission to an intensive care unit is not normally required in someone with hyperglycaemia, unless there are other problems. However, if they have been in a coma for several hours, some brain damage is possible – the doctors will discuss this with you.

What happens in intensive care?

When someone has suffered DKA or HHS, they will need insulin and rapid rehydration using intravenous fluid straight away. They may need to be admitted to an intensive care unit (ICU) where they can receive a high level of care.

In the ICU, they may:

  • have their blood sugar level (BSL) checked frequently using a small finger prick
  • have an arterial line inserted so frequent blood tests can be done to check their BSL and other important chemicals in the blood (once the BSL has fallen, a glucose infusion will probably be started to prevent the BSL from falling too quickly).
  • be connected to a bedside monitor
  • have an indwelling urinary catheter used to accurately monitor urine output, as well as measure the amount of ketones in the urine (this is a good indicator of whether their condition is improving)
  • not have any food or drinks (‘nil by mouth’) until their urine is ketone-free (the nursing staff will discuss this with you)
  • have a nasogastric tube inserted, if they are vomiting
  • have tests carried out to find out why their diabetes became unstable and they developed DKA or HHS.

See Equipment for more detail on the machines and tubes described.

Unless other problems or complications develop, they will most likely only need to stay in the ICU for a few days..

Useful links

Publication details

Version 1.1. First published 2015. Next review 2023.


The information on this page is general in nature and cannot reflect individual patient variation. It reflects Australian intensive care practice, which may differ from that in other countries. It is intended as a supplement to the more specific information provided by the doctors and nurses caring for your loved one. ICNSW attests to the accuracy of the information contained here but takes no responsibility for how it may apply to an individual patient. Please refer to the full disclaimer.