Insulin Injections 101

How you inject your insulin can be critical to receiving its full benefits. You want to know that you’re actually absorbing the medication that you’re injecting, and that your body is able to use it in so many of its ongoing functions! In a recent study by Misnikova and colleagues1, people with diabetes (PWD) that received training on how to inject correctly, including using a new needle for every injection, rotating injection sites, and moving to a shorter 4mm or 5mm needle, experienced a 1% mean reduction in A1C after 6 months.1 And an additional study in Canada, by Bari and colleagues2, found that amongst 230 patients across 24 sites, all patients surveyed made at least one insulin injection error2.

Injections can definitely be intimidating, and they can be a true source of anxiety for some. But, if you just break it down into easy-to-follow steps, you’ll be injecting with confidence in no time.

Drawing insulin into a syringe:
1. Double-check that your insulin vial is the correct one and that there aren’t any clumps or particles in it (as well as the expiration date).
2. Remove the cap from the needle, and pull back on the plunger to draw in the amount of air that is equal to your insulin dose.
3. With the vial upright, insert the needle into the rubber stopper on top of the vial, push the plunger down until all of the air is in the vial.
4. Now turn the vial and syringe upside down (the vial should be above the syringe), and pull the plunger to fill the syringe to the desired dose.
5. Check for large air bubbles, if you see some push the plunger until the bubbles are removed from the syringe.
6. You can now remove the syringe from the vial (make sure the needle doesn’t touch anything until you’re ready to inject).

Preparing an insulin pen for injection:
1. Ensure you have the proper insulin in your pen, and check the expiration date.
2. Attach a fresh pen needle (screw or click the needle securely in place) and remove the outer pen needle cover and inner needle shield.
3. With the needle pointing up, dial one or two units on the pen and press the plunger to prime the pen.
4. Turn the dial to your desired dose.

Delivering the injection:
1. Choose an injection spot that you can see and reach (more later on injection sites and rotations).
2. It’s typically not necessary to wipe your skin with an alcohol swab before injecting, but those at high risk of infection should discuss further with their primary healthcare team.
3. If you’re injecting into an area with limited body fat, you may need to pinch a 1-2” section of skin between your thumb and index finger.
4. While holding the syringe or pen in the palm of your hand, insert the needle at a 90-degree angle to the skin (while making sure the needle is all the way in).
5. While holding the skin pinch, push the plunger with your thumb at a moderate, steady pace until all of the insulin is fully injected. If using a pinch up, let go of the skin after you have injected.
6. Pull out the needle at the same angle at which you inserted it.
7. Dispose of your used needle according to the standards of your local sanitation department (in a thick plastic container with a tight closure).

Needle Length
Insulin injections are meant to be “subcutaneous” (meaning applied under the skin).3 Insulin works best when injected into the fat layer just below the skin.3 Accidentally injecting insulin too deeply (into muscle) can cause pain or an unexpected low blood sugar from a change in uptake and action.4 Longer needles can increase the risk of injecting into muscle. A 4mm pen needle is the recommended needle length for patients as it is safe, effective, and less painful than longer needles.4

Reusing Needles
While insulin pens are meant to be used many time, a new pen needle should be attached to the pen for each injection. We know that many patients reuse their needles (~50%) and there are many reason and circumstances associated with this5. An easy tip for making sure you always have fresh pen needles is to check your needle supply every time you refill your insulin to ensure you have enough supplies.

Insulin Injection Sites
While I’m sure you may have your favourite injection sites, injecting in the same spot repeatedly can cause lumps/swelling and thickened skin (known as lipohypertrophy or “lipo”) that may keep insulin from absorbing properly. Lipo is a lump of fat under your skin caused by repeated injections in the same place. This is why it’s important to regularly rotate your injection sites around your abdomen, outer thighs, buttocks, and upper outer arms.

Injection Site Rotation
Injection site rotation appears to be the most important factor for preventing lipo6. The 4 sites of the body recommended for insulin injections are the upper outer arms, abdomen, buttocks, and upper outer thighs. Once a site is chosen, it should be divided into 4 sections, or halves when using the thighs or buttocks. Use 1 section per week, and rotate injection sites within that section, making sure to always inject at least a finger’s width away from the last injection site4.

Hopefully these tips acted as reminders for those of you that are injection pros, and helpful guidance for those of you that are new to the insulin game. It only takes a few times before you’ll gain the confidence you need to inject in your sleep!

Thank you to embecta for sponsoring this article.

References
1. Misnikova IV, Gubkina VA, Lakeeva TS, Dreval AV. A randomized controlled trial to assess the impact of proper insulin injection technique training on glycemic control. Diabetes Ther. 2017;8:1309-1318.
2. Bari B, Corbeil MA, Farooqui H, et al. Insulin injection practices in a population of Canadians with diabetes: an observational study. Diabetes Ther. 2020;11:2595-2609.
3. American Diabetes Association. Diabetes: Standards of Medical Care in Diabetes—2022. Diabetes Care. 2022;45(1):S1-S259.
4. Frid AH, Kreugel G, Grassi G, et al. New insulin delivery recommendations. In: Mayo Clinic Proceedings. Vol 91. Elsevier; 2016:1231-1255.
5. Frid AH, Hirsch LJ, Menchior AR, Morel DR, Strauss KW. Worldwide injection technique questionnaire study: population parameters and injection practices. In: Mayo Clinic Proceedings. Vol 91. Elsevier; 2016:1212-1223.
6. Blanco M, Hernández MT, Strauss KW, Amaya M. Prevalence and risk factors of lipohypertrophy in insulin-injecting patients with diabetes. Diabetes Metab. 2013;39(5):445-453.