Jessica Oosthuizen shares some useful pointers when injecting insulin.

Insulin therapy remains a fundamental and essential part of diabetes management. Many patients with Type 2 diabetes and all patients with Type 1 diabetes require insulin to keep blood glucose within target ranges.

However, this practice is still not performed optimally in many healthcare facilities, and insulin therapy is only effective if delivered into the correct tissue in the correct way.

The goal of exogenous insulin (insulin that is not made by the body but injected) is to reliably deliver the medication into the subcutaneous tissue, without causing any pain or discomfort and without any leakage of insulin.

The aim is to prevent injecting into the muscle. Injecting into the wrong space can affect the absorption and action of insulin. This can lead to unpredictable blood glucose control. To achieve this objective, it is important to select a needle that is the correct length.

What needles should be used for injecting insulin?

Studies have shown that shorter needles of 4mm are as safe and well-tolerated in comparison to longer ones.

Needles come with a different diameter and length. Those with a higher gauge number have a smaller needle diameter. Needles are available in 4-, 5-, 6- or 8-mm. Needles with a length of 12,7mm have an increased risk of intramuscular injection (which you want to avoid).

It is often assumed that a heavier person, with a higher BMI, may require a longer needle. However, we now know that 4-, 5- or 6-mm needles are suitable for all people with diabetes. Regardless of their BMI.

Insulin therapy should ideally be started using shorter length needles and these injections should be given at 90 degrees to the surface of the skin.

Children and teenagers

Children and adolescents should only be using needles with a length of 4-, 5- or 6mm. There is no clinical reason for using needles longer than 6mm. When injecting insulin into limbs, a skin-fold may be necessary, especially when using a 5- or 6mm needle.

Adults

In adults, including those with a high BMI in the overweight or obese category,  a needle that is 4mm, 5mm or 6mm in length should be used. There is no clinical reason to be using a needle >8mm. Patients who are using these needles should ideally change to a shorter needle. If this is not possible then lifting a skin-fold and/or injecting at a 45 degree angle should be adopted to avoid an intramuscular injection.

Injecting insulin into the muscle will cause: your body to absorb it too quickly; a more painful injection; and a shorter duration of insulin action time.

How many times can you use the same needle?

In a perfect world insulin needles would be used once and then safely discarded. Yet, realistically it’s common practice for needles to be reused. Especially, in a country, like South Africa, where resources are limited in both state and private sectors.

Although the risk of complications is relatively low in relation to the reuse of needles, some evidence does show that the reuse of needles can cause an increased risk of lipohypertrophy. This refers to swelling of the fatty tissue under the skin which causes fat lumps. It’s a relatively common side effect of insulin injections and can occur if multiple injections are given around the same area repeatedly.

Lipohypertrophy causes inconsistent and unpredictable insulin absorption, which can result in unexplained hypoglycaemia and glucose variability. It is for this reason that proper rotation of injection sites and regular changing of needles is essential.

Priming your pen

It’s important to remember that your insulin pen device should always be primed before the first dose and after every needle change.

Priming helps to remove any air bubbles that can collect during everyday use of your pen and ensures that you receive the full dose when administering insulin.

To prime your pen, dial up 2 units, hold your pen with the needle facing upwards and press down on the plunger. If you see drops of insulin come out at the top of the needle, then you know that your pen has been primed.

However, if you don’t see a flow of insulin then you must repeat the steps and continue until drops of insulin are visible at the top of the pen.

These same steps can be followed if you notice an air bubble in your pen. If an air bubble is present and you don’t remove it then you will not receive the correct dose of insulin.

You will notice this when you inject yourself. The air bubble causes a negative pressure when pointing the needle downwards into your skin and you will see a flow of insulin that is not injected and rather ‘spills’ out when removing the needle.

Final comment

Choosing the correct needles and ensuring removal of air when priming your insulin pen are two things that are easy enough to do. They can have positive effects on blood glucose control for people living with diabetes requiring multiple daily injections.

References

1. FIT forum for injection technique in South Africa. Recommendations for best practice in injection technique. 1^st 2014.
2. Kreugel, G., Keers, J., Kerstens, M. and Wolffenbuttel, B. (2011). Randomized Trial on the Influence of the Length of Two Insulin Pen Needles on Glycaemic Control and Patient Preference in Obese Patients with Diabetes. Diabetes Technology & Therapeutics, 13(7), pp.737-741.
3. Shah, R., Shah, V., Patel, M. and Maahs, D. (2016). Insulin delivery methods: Past, present and future. International Journal of Pharmaceutical Investigation, 6(1), p.1.
4. Frid, A., Kreugel, G., Grassi, G., Halimi, S., Hicks, D., Hirsch, L., Smith, M., Wellhoener, R., Bode, B., Hirsch, I., Kalra, S., Ji, L. and Strauss, K. (2016). New Insulin Delivery Recommendations. Mayo Clinic Proceedings, 91(9), pp.1231-1255.
5. Bahendeka, S., Kaushik, R., Swai, A., Otieno, F., Bajaj, S., Kalra, S., Bavuma, C. and Karigire, C. (2019). EADSG Guidelines: Insulin Storage and Optimisation of Injection Technique in Diabetes Management. Diabetes Therapy, 10(2), pp.341-366.

MEET OUR EXPERT

Jessica Oosthuizen is a registered dietitian and works in private practice at the Wits Donald Gordan Medical Centre. Being a Type 1 diabetic herself, since the age of 13, Jessica has a special interest in the nutritional management of children and adults with diabetes. She also has a key interest in weight management and eating disorders.