Insulin overview

Easy-to-read medicine information about insulin – what it is, how to use insulin safely and possible side effects.

Key points

  1. Insulin in our body is made by our pancreas so if the insulin-producing cells in our pancreas are damaged, (such as in type 1 diabetes and over time in type 2 diabetes) then we need to replace this insulin to help our bodies function well.
  2. Insulin cannot be taken by mouth as a tablet because it is inactivated by our digestive enzymes.
  3. Insulin needs to be taken as an injection, just under the skin so it can be absorbed into the bloodstream and travel around the body to help glucose get into our cells and give us the energy we need for daily life.

Types of insulin

There are different brands of insulin available in New Zealand and these are grouped by the time it takes for the insulin to work.

Type of insulin Description
Rapid acting insulin
  • Usually works straight away, so it is injected just before or with food. Its effect lasts 1 to 2 hours.
  • Examples:
    • NovoRapid
    • Apidra
    • Apidra Solostar
    • Humalog
Short acting insulin
  • Usually works within 15 to 20 minutes, so inject each dose 15 to 20 minutes before you eat. Its effect lasts 3 to 4 hours.
  • Examples:
    • Actrapid
    • Humulin R
Intermediate and long acting insulin
  • Usually works after about 1 hour. Its effect lasts all day and may be injected once or twice a day.
  • Examples:
    • Protophane
    • Humulin NPH
    • Lantus
    • Lantus Solostar
    • Levemir (not subsidized in New Zealand) 
Premixed insulin
  • These insulins are a mixture of short and intermediate acting insulins.
  • These may be injected twice a day, in the morning, before breakfast and before dinner. Pre-mixed insulin must be injected before dinner, rather than before bedtime. 
  • Examples:
    • NovoMix 30 FlexPen
    • PenMix 30
    • PenMix 40
    • PenMix 50
    • Humulin 30/70
    • Mixtard 30
    • Humalog Mix 25
    • Humalog Mix 50


Your doctor or nurse will work with you to find the best insulin to meet your needs. This can be made up of a rapid acting insulin and an intermediate or long acting insulin, or it can be insulin and tablets.

How to use insulin

  • The timing of your insulin in relation to food and exercise  is important. Your doctor or nurse will advise you when it is best to use your insulin.
  • It is best to avoid hot showers or baths within 30 minutes of an insulin dose.
  • Your doctor or nurse will advise what to do if you miss a dose of insulin.
  • Drinking alcohol can affect blood glucose and the dose of insulin may need to be changed. Avoid or limit alcohol intake.
  • If you are unwell and not eating as you usually do, your insulin dose may need to be changed. Contact your doctor or nurse for advice.

Injection sites

  • Insulin should be injected into the fatty tissue under the skin. The abdomen or tummy area, about 5 cm away from your belly button, is usually a good place. It is easy to reach and insulin absorbs well from this area.
  • Other areas such as the buttocks, thigh or outer arm are usually not preferred because they are harder to reach, insulin is absorbed slower and absorption may be affected by exercise.   
  • Move injection sites so that the skin does not become lumpy. Lumpy skin can affect how your body absorbs insulin.  You can move from one side of your abdomen to the other side each time.  
  • Do not inject insulin on any scar tissue.

Read more about injecting insulin and insulin pens, syringes and needles.

How to store insulin

  • Unopened insulin can be stored in the fridge until it is used.
  • Do not store insulin in the freezer.
  • Once opened, insulin vials, cartridges or pre-filled pens can be kept at room temperature but must be discarded after 28 days.

Side effects when using insulin

  • Sometimes insulin may lower your blood sugar too much – called hypoglycaemia. This may cause you to feel weak, faint, dizzy, drowsy or irritable. You may get a headache, tremor (shakes) or blurred vision. If this occurs, drink something sweet such as a small glass of sweetened soft drink, or fruit juice, or eat something sweet such as lollies. Make sure your family and friends know what to do too. Tell your doctor or nurse if this happens a lot. Your dose of insulin may need to be changed.
  • Pain or redness at the injection site – change the injection site and contact your doctor or nurse if the pain or redness continues.


Insulin interacts with some other medications and herbal supplements so check with your doctor or pharmacist.

Learn more

Medsafe Consumer Information Sheets:

New Zealand Formulary Patient Information:

Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 05 Apr 2017