Insulin for type 1 diabetes

There are three main reasons to treat diabetes with insulin:

  • to relieve the symptoms of diabetes, including increased thirst and needing to urinate frequently
  • to keep blood glucose as close as possible to recommended levels
  • to reduce the risk of developing the complications of diabetes, such as heart disease, kidney disease, eye disease, and foot and leg problems.

What does insulin do?

Insulin is a hormone produced by the pancreas (an organ found behind the stomach). When blood sugar (glucose) levels rise — for example after a meal, insulin controls glucose levels in the body, by causing the liver, muscle and fat tissue to take up glucose from the blood. If you have type 1 diabetes, your body produces little or no insulin, so a manufactured insulin can be injected instead. The manufactured insulin does exactly the same job as your body’s own insulin would.

For more information, read our page on injecting insulin.

What are the benefits of using insulin?

Insulin is commonly prescribed for diabetes. The benefits and side effects of most forms of insulin have been observed for many years and are well understood, unlike newer medicines. Importantly, most forms of insulin have been shown to reduce the complications of diabetes, a very important benefit of these medicines.

Insulin is:

  • used to treat type 1 diabetes and gestational diabetes
  • sometimes used to treat type 2 diabetes
  • used for anyone with diabetes if they have a short-term illness or are having surgery
  • available in different types of insulin (e.g. slow- or fast-acting) and forms (vials, cartridges, or pre-filled pens), and from different sources (i.e. human insulin or manufactured human insulin).

For more information, see our list of the types and forms of insulin available in Australia.

Who can use insulin?

Insulin can be used by:

Types of insulin

Insulin is available in several different types and forms (vials, cartridges, or pre-filled pens), which come from different sources (human, manufactured, and less commonly bovine [from cattle]), and differ in how quickly they work (very short-acting, short-acting, intermediate-acting, and long-acting) and how long they last in the body (4–24 hours).

Types of insulin include:

  • very short-acting — insulin levels are highest at 1 hour after injection but continue to work for 4–5 hours (e.g. Apidra, Humalog and NovoRapid)
  • short-acting — insulin levels are highest 2–3 hours after injection but continue to work for 6–8 hours (e.g. Actrapid, Humulin R and Hypurin Neutral)
  • intermediate-acting — insulin levels peak between 4 and 12 hours and continue to work for 16–24 hours (e.g. Humulin NPH, Protaphane and Hypurin Isophane)
  • long-acting — the insulin works for up to 24 hours (e.g. Lantus and Levemir); Lantus has no peak and remains active for up to 24 hours after injection, while Levemir insulin levels peak at 9 hours and remain active for 12–24 hours after injection
  • pre-mixed — this type of insulin is a mix of different amounts of short-acting and intermediate-acting insulin (e.g. Humalog Mix 25, Humalog Mix 50, NovoMix 30, Mixtard 30/70, Humulin 30/70 and Mixtard 50/50).

The different types of insulin will differ in the number of insulin injections needed per day, the size of each dose, and the timing of the injection. The aim is to keep insulin levels as steady as possible over a 24-hour period to cover rises in blood glucose levels following meals and to keep glucose levels within the desired range.

There are often many different brands of one medicine, in this case, insulin. To find out more, read our information about active ingredients and brand names.

See our list of the types and forms of insulin available in Australia.

For more information about how insulin is injected, see our pages on injecting insulin and insulin pumps.

What are the side effects of insulin?

  • Weight gain is likely with insulin.
  • Hypoglycaemia (low blood glucose) is more likely with insulin than with other medicines for diabetes. Most often, hypoglycaemia is caused by using a larger dose of insulin than normal, eating late or missing meals, not eating enough food, or increased physical activity.

Allergic reactions are possible but this is rare.

Some people get skin reactions at the injection sites.

Who can I ask about side effects?

If you are concerned that you may have had side effects related to a medicine, seek medical advice. To report and discuss possible side effects, call the Adverse Medicines Events (AME) line on 1300 134 237 from anywhere in Australia (Mon–Fri, 9am–5pm).


It is important to tell your health professional about all the medicines you are taking — including prescription, over-the-counter and complementary medicines (herbal, ‘natural’, vitamins and minerals) — as they may interact with your injected insulin and affect your blood glucose levels. This may mean that your health professional will need to adjust your dose of insulin, or make changes to your other medicines.

Some medicines are known to affect blood glucose levels. Click on the following links to view tables that list some of these medicines:

Apart from these, other medicines that may interact with insulin include:*

  • ACE inhibitors — used to treat high blood pressure (hypertension), heart failure, heart and circulatory (cardiovascular) problems in people with heart disease, and to prevent kidney disease in people with type 1 diabetes — these may increase insulin sensitivity and a lower dose of insulin may be needed
  • other blood pressure lowering medicines (antihypertensives), including diltiazem and nifedipine, may raise glucose levels
  • thyroid hormones may raise blood glucose
  • some antibiotics may decrease blood glucose (e.g. high doses of sulfonamides and some tetracyclines)
  • antidepressant medicines (e.g. amitriptyline and fluoxetine).

*As there are often many different brands of one medicine, we have only listed the active ingredients of the medicines here. To find out more, read our information about active ingredients and brand names.

Phone for medicines information

Call NPS Medicines Line on 1300 MEDICINE (1300 633 424) to get information about your prescription, over-the-counter and complementary medicines from a pharmacist.

  • Craig ME, Twigg SM, Donaghue KC, et al for the Australian Type 1 Diabetes Guidelines Expert Advisory Group. National evidence-based clinical care guidelines for type 1 diabetes in children, adolescents and adults. Canberra: Australian Government Department of Health and Ageing, 2011. (accessed 15 November 2011).
  • Rossi S, ed. eAMH [online]. Adelaide: Australian Medicines Handbook, July 2012.
  • Sweetman S, ed. Martindale: The complete drug reference [online]. London: Pharmaceutical Press. (accessed 18 October 2011).
  • Baxter K, ed. Stockley's drug interactions: A source book of interactions, their mechanisms, clinical importance and management. 9th edn. London: Pharmaceutical Press, May 2010. (accessed 18 October 2011).
  • The relevant consumer medicine information and product information have been consulted for every medicine discussed.