Blood Glucose, Insulin and Diabetes

What is glucose?

Glucose is a type of sugar needed to produce energy in the human body and is broken down from carbohydrates. Carbohydrates are found in many foods including bread, potatoes, fruit, milk and rice. Once inside the body, glucose needs to move from the bloodstream into our cells where it is converted into energy or stored. This process is called glucose metabolism.

What is a normal blood glucose level?

A normal blood glucose level is between 4.0 and 7.8 mmol/L of blood, although levels can rise within the first few hours after eating.  When blood glucose levels are too high, individuals are at risk of hyperglycaemia.  Conversely, a condition known as hypoglycaemia occurs when blood glucose levels are too low.

Diabetes is diagnosed when these levels reach or exceed 11.1 mmol/L, a condition known as hyperglycaemia.

What is insulin?

Insulin is a hormone secreted by the pancreas and allows glucose to go from the blood stream to the cells. However, in people with diabetes, the pancreas either doesn’t produce insulin at all (Type 1 diabetes) or it can’t keep up with the levels required by the body to regulate glucose levels (Type 2 diabetes).

When this happens, the body cannot move glucose into the cells resulting in abnormally high glucose levels. This excess glucose builds up in the blood and can lead to health complications associated with diabetes.

Using insulin to manage diabetes

While there is no cure for diabetes, there are a number of measures that can be taken to prevent associated health issues such as kidney damage, heart disease and poor circulation. This can include regulating blood glucose levels, making lifestyle changes to help moderate body weight, and the maintenance of healthy blood pressure and cholesterol levels.

In Type 1 diabetes, little or no insulin is produced as the cells that make it have been damaged by an autoimmune reaction. Therefore, those diagnosed with Type 1 diabetes will need to inject insulin every day to maintain healthy blood glucose levels.

In Type 2 diabetes, lifestyle changes may delay the need for insulin injections initially, although it is likely that eventually they will be required.

Types of insulin

There are five types of insulin available, listed below. As each person responds differently to the insulin they take, their GP will advise on the appropriate type and amount needed to manage their condition.

  • Rapid onset or fast-acting insulin

    Clear in appearance and can take up to 20 minutes to take effect, peaking at around 60 minutes. This type of insulin lasts in the bloodstream for between 3-5 hours and it is essential that food is eaten immediately after it is administered.

  • Short-acting insulin

    Clear in appearance and takes effect within 30 minutes. It must be administered half an hour before eating and lasts between 6 to 8 hours, peaking at around the two-hour mark.

  • Intermediate-acting insulin

    Cloudy in appearance and has its effect delayed by the addition of either protamine or zinc. Lasting between 16 to 24 hours, intermediate-acting insulin gets to work within 90 minutes and peaks between four and 12 hours.

  • Mixed insulin

    Cloudy in appearance and combines a rapid onset / short-acting insulin and intermediate-acting insulin in one injection. People with diabetes can administer this insulin just before eating to keep insulin levels stable for some time after they’ve had their meal.

  • Long-acting insulin

    Clear in appearance and lasts for up to 24 hours. It doesn’t typically peak, so levels are sustained throughout the entire 24 hour period.


Diabetes management requires self-awareness in knowing what makes your blood sugar rise and fall – and how to control these factors day-to-day. The key comes...
Woman working out Australian Diabetes statistics
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