What is Diabetes?

Diabetes is a group of conditions where the level of glucose (sugar) in the blood is higher than it should be.

This happens because of problems with a hormone called insulin, which helps move glucose from the bloodstream into the body’s cells to be used for energy.

Insulin is the key

Glucose, from the sugars and starches that we eat, is transported in the bloodstream. Insulin is needed for glucose to leave the bloodstream and enter the body’s cells where it is burned to provide energy. Without insulin, cells are deprived of glucose and energy, and the blood glucose level rises.

Which TYPE of Diabetes? The ‘Type’ of diabetes depends on the underlying cause of the high blood glucose level: 9 times out of 10 this is down to insulin not working properly and over a period of years less and less insulin is produced; this is Type 2 diabetes (T2DM) Approximately 1 in 10 cases of diabetes occurs due to the destruction of the insulin-producing cells, usually down to the body’s immune system turning on itself. When this happens no insulin is produced; this is Type 1 diabetes (T1DM). The third common form of diabetes occurs during pregnancy, and usually lasts only for the duration of the pregnancy, although many women will then go on to develop Type 2 diabetes later on in life. This type of diabetes is called Gestational diabetes (GDM). You can find a full breakdown of all the various Types of diabetes on the ‘Classification of Diabetes’ page.

The Effects of High Blood Glucose Levels

When blood passes through the filtering system in the kidneys, glucose is normally retained; but when the blood glucose level rises too high, glucose ‘spills over’ into the urine. This makes the urine so concentrated that extra water is drawn out too. People with untreated diabetes therefore produce large volumes of urine, becoming dehydrated and very thirsty. Fungal infections (such as thrush) thrive in the moist sugary environment of the genital area and can prove to be a persistent problem in people with diabetes.

In the absence of insulin, the body’s cells are not able to take glucose from the bloodstream. Messages are sent to the liver to release glucose from its stores because the cells believe that the body is in starvation. The blood glucose level rises… In desperation, cells turn to fats as a fuel instead. Burning up fats yields chemicals known as ketones. If these are produced faster than they can be disposed of by the body, they build up in the bloodstream and become toxic. Ketones make the blood too acidic and messages are sent from the brain to the lungs to breathe faster. You can smell ketones on the breath – fruity, like pear drops. If left untreated then vomiting, drowsiness and eventually coma will result. This life-threatening state is called diabetic ketoacidosis or DKA. It is usually only a potential problem for people with Type 1 diabetes.

>> More on Diabetic Ketoacidosis (DKA)

Prolonged severe high blood glucose levels in people with Type 2 diabetes may lead to a condition known as ‘hyperosmolar non-ketotic coma‘ (HONK) also referred to as hyperosmolar hyperglycaemic state (HHS). This is caused by extreme loss of fluid (dehydration) and the resulting chemical imbalance in the blood.

>> More on Hyperosmolar Hyperglycaemic State (HHS)

Over a period of years, high blood glucose levels can cause damage to numerous body tissues, including the eyes, nerves, kidneys and heart. These ‘complications’ are chiefly the result of damaged blood vessels.

>> More on Long Term Complications of Diabetes

---

Page updated: April 2026

---

INTRODUCING DIABETES
Newly Diagnosed
What is Diabetes?
Diabetes and Insulin
Classification of Diabetes
Monogenic Diabetes
Diagnosing Diabetes
Managing Diabetes
Food Choices
Blood Glucose Levels and HbA1c
Hypoglycaemia (Low Blood Glucose)

LEGAL DISCLAIMER: The information on this website is provided for general educational purposes only and is intended for a New Zealand audience. It is not a substitute for professional medical advice, diagnosis, or treatment. While I strive to ensure accuracy and relevance, please always seek guidance from your healthcare provider for personal medical decisions. Use of the content is at your own risk. Links to other sites are for convenience and do not imply endorsement.