Currently, the only way to get insulin into the body is by injecting it. Most people with diabetes not already using insulin dread the thought of injections. However, the benefits of bringing blood glucose under control make it worth overcoming this fear. The good news is that insulin injections today are quite painless. Technology has advanced. Needles are finer and shorter than ever before, but still deliver insulin effectively.
Insulin delivery devices have come a long way since the days of the needle and syringe. Although syringes are still available, most people who inject insulin daily use a pen delivery device. Whether you choose an insulin syringe or pen, the cost is comparable.
An insulin pen can be a pre-filled pen, or a re-useable pen that is reloaded with insulin cartridges. Each injection requires a new pen needle (or tip) to be attached to the pen before the injection. After the pen needle has delivered a dose of insulin, it must be safely discarded into an approved sharps container. Another method is to clip the needle off using a safe-clip device.
Use each pen needle only once. Reusing a pen needle can cause various problems at the injection site. Problems include lipodystrophy (build-up of lumpy fat tissue), pain, bleeding, bruising, or even having a needle break off under the skin. Pen needles are coated with a lubricant for a smoother insertion into the skin. This lubricant will not be as effective in further injections.
Before attaching the needle to the pen, make sure the paper safety seal is completely protecting it. As well, check the needle by doing a two-unit priming dose. This ensures it has no blockages.
Pen needles are universal fit. This means that all needles sold in Canada will fit all insulin pens available in Canada. Health care providers can help check that a pen needle is compatible with the pen. Most pen needles attach onto the insulin pen by screwing on the tip. Others, such as the Penfine® Universal Click™ pen needles, just click into place and then unscrew like regular pen needles. Click-on pen needles are helpful for those who have trouble with vision or issues like arthritis that affect the hands.
Injection site, insulin dose, injection technique, body composition, and your age all influence the length and type of pen needle you should choose. Pen needles come in various gauges and lengths. The gauge is the diameter or thickness of the needle. The greater the gauge (G) number, the thinner the needle. The length of a pen needle is measured in millimetres (mm). The needle can be as short as 4 mm, to as long as 12.7 mm. The length of the needle determines how deep into the skin's surface the insulin will be deposited.
A wide selection of needle lengths and gauges are available. Picking a pen needle that will best deliver the proper dose of insulin can be confusing. Insulin must be put into the subcutaneous (under the skin) tissue for it to work properly. Injecting too deeply could deliver insulin to the muscle, where it is absorbed too quickly. This means its action may not last as long as intended. Injecting too shallowly deposits insulin in the skin. This is painful and prevents the body from absorbing the insulin. Using the right pen needle helps ensure that insulin is injected where it has the best effect.
Injection site: On average, human skin is two mm thick. Four areas on the body can be used for injecting insulin: the abdomen, upper arms, thighs and buttocks. Insulin works most quickly when injected into the abdomen. After this, the upper thigh and the buttocks are the faster sites. Short-acting insulin is usually injected into the abdomen so it can take rapid effect right before mealtime. Long-acting insulin is usually injected into the upper thigh or the buttocks because the length of action is longer there. The average thickness of the skin at each of the four sites is: abdomen 2.2 mm, upper arm 2.2 mm, thigh 1.9 mm and buttocks 2.4 mm. This means that no matter which injection site you choose, there will only be about half a mm difference in skin thickness.
Insulin dose: Insulin doses can range from a tiny 0.5 unit up to 90 units. A smaller gauge pen needle is best for large doses of insulin (anything over 30 units). A smaller gauge needle, which has a larger diameter, allows a larger volume of insulin to flow through faster and with greater ease.
Injection technique: The skin at the injection site may be lifted up to make a skin fold. This reduces the risk of injecting past the subcutaneous layer and into muscle. Use the skin lift method of injection with pen needles 8 mm or greater in length. A skin lift is not necessary when using pen needles 6 mm or shorter. The easiest way to inject is to insert the needle straight into the skin at a 90-degree right angle without a skin lift. However, if the injection site has very little fat, a 45-degree insertion angle and skin lift may be needed to prevent reaching the muscle.
Body composition: The amount of body fat is another factor to consider when choosing a pen needle length. Body mass index (BMI) is one way to measure body fat. It has long been thought that overweight individuals require a longer needle to penetrate the skin. However, recent studies show that the skin thickness difference between someone with a BMI of 25 (overweight) compared to a BMI of 35 (obese) is only 0.2 mm.
Age of user: The subcutaneous layer under the skin of a young child or teenager can be readily reached with a shorter needle length. In most cases, a four mm needle length will be sufficient. In adults, however, a longer needle length may be needed to ensure insulin is deposited into the subcutaneous fat.
Which pen needle is the best choice? The one that causes the least pain while delivering insulin most effectively. The shortest and finest pen needle will be the least painful. It may also relieve anxiety that you may have at first about needles and injecting insulin.
A good starting pen needle choice for someone beginning insulin would be either a four or five mm pen needle. These shorter needle lengths are effective for people of all sizes and ages. These are long enough to pass through the skin into the subcutaneous tissue, but short enough not to penetrate the underlying muscle layer. The short needle length also means no skin lift is needed. Putting the needle straight in at a 90 degree angle will not push the needle tip into muscle tissue.
Insulin injection with these very short, fine needles is quite pain-free. If you or someone you know requires insulin, please do not think that injections must be painful or scary. Rather, insulin injections can be an easy, comfortable way to manage diabetes more successfully.