What is diabetes?

Diabetes is a condition where the level of glucose (a type of sugar) in your blood is too high. If not controlled, high blood glucose levels eventually lead to damage in many parts of your body.

The amount glucose in your blood is controlled by several different hormones but the main one is insulin. After a meal, some of the glucose in the food is used immediately as fuel and the rest is stored for using later. Some parts of your body, in particular the brain, must have a good supply of glucose to function properly.

This page provides general information about diabetes. Learn more about different types of diabetes

What is insulin?

Insulin is a hormone produced by your pancreas. When the amount of glucose in your blood increases, the pancreas releases more insulin. When the level of glucose in your blood falls again, the amount of insulin also falls.

Insulin acts like a key, unlocking a channel to allow glucose from food to move from your blood into your body's cells. Insulin also makes your body store glucose in your liver and muscles. If there is not enough insulin, or it is not working well, glucose builds up in your bloodstream.

With diabetes, your body does not produce enough insulin to keep the amount of glucose in your blood at the right level. This can be due to your body not making enough insulin (known as insulin deficiency), not responding to insulin as it should (known as insulin resistance) or a combination of both of these.

The video below describes how diabetes, glucose and insulin work in type 2 diabetes. Watch more videos about diabetes.

(Visual GP, NZ, 2015)

What is normal, high and low blood glucose?

The normal level of glucose in the blood is between 4 and 8 mmol/L. When blood glucose levels go higher than this, your body uses glucose as fuel and stores the extra glucose for use later. When the blood glucose levels go lower than this, your body will release glucose from your liver so it can be used as fuel.

If the level of glucose in your blood is too high, hyperglycaemia (high blood glucose) can occur. Symptoms depend on how high or how quickly the level changes. They can include being really thirsty, peeing lots and blurred vision. Unfortunately, most people do not know they have high blood glucose unless they have a blood test. Long term, high glucose levels cause damage to your eyes, kidneys, blood vessels, heart and feet. 

If the level of glucose in your blood drops too low, hypoglycaemia or a ‘hypo’ can occur. You may feel sweaty, weak and dizzy. You need some glucose right away. Low blood sugar can be dangerous if it's not treated promptly, but you can usually treat it easily yourself. Read more about hypoglycaemia

What is the difference between type 1 and type 2 diabetes?

Type 1 diabetes  

The main problem in type 1 diabetes is that the insulin-making cells in your pancreas are destroyed so it can’t make enough insulin. Type 1 diabetes often starts in childhood and can appear with little warning. About 10% of people with diabetes have type 1 diabetes. Read more about type 1 diabetes, including causes, symptoms, diagnosis, treatment and self-care.

Type 2 diabetes

The main problem in type 2 diabetes is that your body can’t use insulin effectively. The insulin-making cells in your pancreas can produce insulin, but the insulin isn’t able to work well because the cells in your body no longer respond to its effects. Sometimes, the pancreas becomes exhausted. This leads to not enough insulin production on top of the problem of insulin resistance. About 90% of people with diabetes have type 2 diabetes. 

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

What is pre-diabetes?

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

Finding out you have pre-diabetes can be an opportunity to make changes and stop it progressing to type 2 diabetes. The best things you can do to prevent or delay pre-diabetes progressing to diabetes are to get to a healthy body weight, make healthy food and drink choices and exercise regularly.

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

What do I need to know about diabetes and pregnancy?

If you have diabetes (type 1 or type 2) before you get pregnant it is known as pre-existing diabetes and pregnancy. This is different from gestational diabetes, which is a kind of diabetes that some women get during pregnancy. 

Pre-existing diabetes and pregnancy

Having high blood glucose levels because of type 1 or type 2 diabetes can affect all stages of pregnancy, from conception to delivery. But, if you maintain healthy blood glucose levels before and during your pregnancy, you have the same chance of delivering a healthy baby as all other women. Read more about diabetes and pregnancy, including advice for preparing for and managing diabetes during pregnancy.

Gestational diabetes 

Gestational diabetes is when a pregnant woman who was not known to have diabetes before pregnancy develops high blood glucose levels during pregnancy. It affects about 4–8% of pregnant women. It needs to be managed carefully to improve the health of mum and pepi/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 diabetes, including causes, symptoms, diagnosis, treatment, prevention and self-care.

Diabetes – overview and symptoms

Experts explain what diabetes is and the symptoms it causes and Annette talks about her experience with diabetes.

(Health Navigator Charitable Trust and Synergy Film, NZ, 2014)

Diabetes overview – causes

The causes of type two diabetes, risks and what you can do to prevent getting diabetes.

(Health Navigator Charitable Trust and Synergy Film, NZ, 2014)

How is diabetes diagnosed?

In most cases the diagnosis of diabetes is simple. A blood test called an HbA1c measures the amount of glucose that has built up in your blood over a 3-month period. A high HbA1c result (or two if you do not have any symptoms of diabetes) confirms the diagnosis. In most cases no other test is necessary, but tests to measure the amount of glucose in your blood may also be used. Read more about the HbA1c test.

In the past, urine tests were used to diagnose diabetes, but these are unreliable and no longer used.

Learn more

The Diabetes Action Month website has some patient resources including a Know Your Risk quiz, why LanguageNutritionMovement and Prevention matters, and a Healthy Food Guide eBook 

Reviewed by

Dr Jeremy Tuohy is an Obstetrician and Gynaecologist with a special interest in Maternal and Fetal Medicine. Jeremy has been a lecturer at the University of Otago, Clinical leader of Ultrasound and Maternal and Fetal Medicine at Capital and Coast DHB, and has practiced as a private obstetrician. He is currently completing his PhD in Obstetric Medicine at the Liggins Institute, University of Auckland.
Credits: Health Navigator Editorial Team. Reviewed By: Jeremy Tuohy, Researcher & Clinician, University of Auckland Last reviewed: 16 Oct 2019