D I A B E A S Y

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Insulin is an important hormone produced by the body in the pancreas. It is a protein which means it is made up of base units called amino acids. The image below is the three-dimensional structural form of the molecule insulin.

Insulin allows cells to uptake glucose from the bloodstream by binding to a receptor on the cell membrane. In this case, the orange molecule represents insulin and the blue molecule represents the cell’s receptor which is attached to the plasma membrane.

A simplified diagram shown below represents insulin allowing glucose to enter the cell.

Since insulin is a protein, it has to be stored carefully, otherwise it becomes inactive (denatured). This means that insulin must be stored in the refrigerator when not being used or at room temperature when being used. It will not function properly if subjected to extremes of temperature.

There are also different types of insulin that are used. These vary on what is called their profile of action (i.e. how long it takes for the insulin to act, when does the effect of the insulin peak and how long does it last). These factors are determined by how readily the insulin is broken down into single molecules, how quickly it absorbed from under the skin and how well it binds to insulin receptors. The list below contains some of the different insulin types and their common brand names (N.B. this list is not exhaustive):

  • Rapid-acting insulin (e.g. Novorapid)
  • Short-acting insulin (e.g. Humulin-R)
  • Intermediate-acting insulin (e.g. Protaphane)
  • Long-acting peakless insulin (e.g. Levemir)

Your insulin will be chosen by your medical professional but it is important to understand the different profiles and dosing requirements.

Insulin therapy

In order for patients living with Type 1 diabetes to have adequate blood sugar control, insulin has to be injected into fatty tissue (subcutaneously) where it is then absorbed into the blood stream. There are numerous different insulin types, patterns of injection and methods of insulin injection (e.g. insulin pens and insulin pumps).

In a perfect world, insulin therapy would exactly copy the secretion of insulin by the pancreas. The graph below shows that there are two factors which need to be considered when dosing insulin. A basal injection (usually long-acting insulin) mimics the background levels of insulin which are always present in the body and a bolus injection (usually a rapid-acting insulin) mimics the peaks in insulin levels during mealtimes.

This page will focus on insulin pens but if you are using an insulin pump, please proceed to the next page.

There are different patterns of insulin dosing dependent on what your healthcare professional recommends. The most common routine is the basal-bolus injection plan (also know as multiple daily injections). This consists usually of 3 bolus injections of rapid-acting insulin at breakfast, lunch and dinner as well as once or twice daily a basal injection of long-acting insulin. There are various ways of applying this routine which include

  • Consistent carbohydrate intake (each mealtime, a person has a fairly consistent carbohydrate intake which means insulin dosing requirements remain the same)
  • Flexible carbohydrate and insulin adjustment (each mealtime, a person varies their carbohydrate intake and insulin dosage by taking into account whether they are eating more or less carbohydrates than usual)
  • Insulin to carbohydrate ratio (each mealtime, a person calculates exactly how many units of insulin they need according to their insulin to carbohydrate ration)

The following is a set of general guidelines in order to use insulin pens correctly and safely:

  • Gather all the equipment necessary including the insulin pen (make sure it is the correct on, has sufficient insulin and is not expired), logbook, insulin needle, sharps disposal bin, alcohol swab.
  • Choose an injection site: suitable areas include the abdomen, upper thighs and buttocks. It is importantly to change the site regularly to avoid any lumps forming.
  • Swab the area with an alcohol swab to avoid infection, this can also minimise the pain when the needle goes in.
  • Prepare the insulin pen by placing the needle cap on the pen and turn the knob to 2u of insulin and pointing the pen upwards, push in the knob (air shot). This will ensure the pen is primed.
  • Pinching a bit of your fatty tissue, insert the pen at 90 degrees, deliver the appropriate dosage, and remember to wait 5-10 seconds before removing the pen.
  • Place the lid back on the pen needle and dispose safely in a sharps disposal bin.
  • Record the amount given and time in your logbook.

Honeymoon period

When newly diagnosed, the injection of artificial insulin allows the pancreas to recover and insulin requirements may decrease. This is because the pancreas is still producing some of the required insulin. The time that the honeymoon lasts for is variable but research is underway to see whether tight blood sugar control and other factors may extend this period.