Diabetes overview

Diabetes occurs when there is too much glucose, a type of sugar, in the blood. If not controlled, high blood glucose levels will eventually lead to damage to many parts of the body.

Blood-sugar levels are normally controlled by a hormone called insulin, which is made in the pancreas. High blood glucose levels may be caused by:

  • insulin deficiency – when the pancreas is not able to make enough insulin, or
  • insulin resistance – when your body is not responding to insulin as it should.

What is insulin?

Insulin is a natural hormone that helps glucose enter the body's cells where it is used for energy. If there is not enough insulin, or it is not working well to act as a key to open the channel for glucose to enter the cells, glucose builds up in your bloodstream.

  • The normal level of glucose in the body is between 4 and 8 mmol/L.
  • When you have diabetes, your body is not able to control your blood glucose levels and keep it in the safe range.
  • If the blood glucose level is too low, hypoglycaemia (low blood glucose) occurs and you feel sweaty, weak and dizzy, and need to eat some glucose right away.
  • If the blood glucose level is too high, hyperglycaemia (high blood glucose) can occur.
  • Symptoms depend on how high or rapidly the level changes but can include excess thirst, passing excess urine, blurred vision etc.

What are the common types of diabetes?

There are three main types of diabetes and one type of prediabetes. 

Type 1 diabetes – this is caused by insulin deficiency. It often starts in childhood and can appear with little warning. Approximately 10% of people with diabetes have type 1 diabetes. Read more about 

Read more about type 1 diabetes, including causes, symptoms, diagnosis, treatment and self-care.

Type 2 diabetes – is the most common type of diabetes affecting about 90% of all people with diabetes. With type 2 diabetes, the main problem is insulin resistance, although insulin deficiency can also develop. Approximately 90% of people with diabetes have type 2 diabetes.

Read more about type 2 diabetesincluding causes, symptoms, diagnosis, treatment, prevention and self-care.

Diabetes in pregnancy – this is when you get diabetes during pregnancy. It is also called gestational diabetes. It needs to be managed carefully to improve the health of mum and baby. It usually goes away after having the baby but can progress to type 2 diabetes so regular check-ups are recommended. 

Read more about gestational diabetesincluding causes, symptoms, diagnosis, treatment, prevention and self-care.

Pre-diabetes  this is when your blood glucose (sugar) level is higher than normal, but not high enough to be diagnosed as type 2 diabetes yet. As the rates of obesity and being overweight have increased, so have the rates of prediabetes and insulin resistance. It now affects about 1 in 4 New Zealanders aged 15 or over.

Read more about pre-diabetesincluding causes, symptoms, diagnosis, treatment, prevention and self-care.

Credits: Health Navigator Editorial Team, latest update Oct 2015.