Many people with diabetes take insulin to control their blood glucose levels. People with type 1 diabetes must take insulin every day in order to manage their diabetes. In type 2 diabetes, blood glucose can often be controlled by making changes in lifestyle, such as diet and weight loss. Tablets are often required however, and insulin may also be necessary if these other measures are insufficient to achieve good blood glucose control.
Insulin cannot be given in tablet form and instead is injected under the skin, usually by the patient, or by a parent or carer. The number of injections of insulin taken each day depends on the needs of the individual and the type of insulin used. Most people require between one and four injections per day.
How Does Insulin Treatment Work?
In the absence of diabetes, the pancreas continually releases a low level of insulin throughout the day and night. This is called ‘basal insulin’. Additional boosts of insulin are released at meal times, to manage the increase in blood glucose levels that accompanies the digestion of food. The aim of insulin treatment for people with diabetes is to mimic these normal patterns of insulin production, so that blood glucose levels are controlled throughout the day.
Types of Insulin
Most people who take insulin use a form that has been manufactured to resemble human insulin (also called ‘synthetic’ or ‘recombinant’ human insulin, or human insulin ‘analogues’).
Insulin can be divided into four main groups, according to the time taken for the drug to begin to have an effect on blood glucose, and the length of time over which this effect continues. The following times are approximate, because individual responses vary:
- Rapid-acting insulin analogues. These are used to coincide with mealtimes. They work approximately 15 minutes after injection, peak within about 1 hour, and continue to work for 2-4 hours.
- Short-acting insulins. These are used before a meal. They reach the bloodstream in about 30 minutes, peak after 2-3 hours, and continue to work for 3-6 hours.
- Intermediate-acting insulins. These are used to provide background insulin. They begin to work 2-4 hours after injection, peak 4-12 hours later, and continue to work for 12-18 hours.
- Long-acting insulins. These provide a steady level of background insulin over a longer period of time, about 24 hours.
Mixed insulins (‘biphasic’ insulins) are also available which combine intermediate-acting insulin with either rapid-acting or short-acting insulin.
Insulin dosing schedules are individualised according to the person’s diet and daily activities, their preferences about the number of injections given each day, and their specific needs with regard to blood glucose control (avoiding both hyperglycaemia and hypoglycaemia). Schedules need to be flexible, so that adjustments can be made to fit with changes to daily routine, such as holidays, fasting or periods of ill health (usually called ‘sick day rules’).
Most people with type 1 diabetes opt for treatment with 2 types of insulin, a background or long acting insulin usually taken last thing at night, and a rapid acting insulin taken before meals.
All insulins should be stored at a temperature below 25 degrees C. It is recommended that people keep their insulin in the fridge, except the bottle they are currently using. This bottle should be kept at room temperature, out of direct sunlight and away from heat sources, because injecting cold insulin can be painful. Insulin which has been out of the fridge for more than 28 days should not be used.
Insulin Delivery Systems
Insulin is injected into the fatty layer which is just below the skin. A number of devices are used to do this, either a syringe, an ‘insulin pen’ which has a needle on the end and contains a cartridge filled with insulin, or a needle-free device called a jet injector, which delivers insulin through the skin at high pressure. The image on the right shows a variety of insulin pens.
People who do not respond well to insulin injections may consider using an insulin pump, a small, battery-operated pump that is worn on the body and gives insulin through a fine tube inserted under the skin. The image below shows an insulin pump.
Other methods of delivering insulin such as by mouth or by inhalation devices are subjects of research studies but are not yet in routine clinical practice.
The NHS diabetes website has a tutorial on the practicalities of insulin administration aimed at healthcare professionals.
Download more information from the Community Insulin Start Group below:
Insulin Start Group Completion letter (in pdf format)
Insulin Titration sheet (in pdf format)
Note these files are in Adobe Acrobat pdf format. If you have not installed and configured Adobe Acrobat Reader on your system, a free download is available from Adobe.