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How to Properly Inject Insulin

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Let’s face it: Following medication dosing instructions can be a bit like a game of telephone. You think you remember the exact details, but you may have fudged a few things along the way.

That happens pretty frequently when it comes to injecting insulin, says Melanie Teslik, RN, CDE, a certified diabetes educator at Winthrop-University Hospital in Mineola, New York. “Through time, even if a person has been taught the correct way, they come up with their own methods,” she says.

That’s why it’s a good idea to ask your certified diabetes educator for a refresher on proper technique. (The package insert that comes with your pen or insulin vial can also guide you through the process of injecting.) At the following visit, review the steps to reinforce good practices.

So, where do you start? Whether you use a pen or a vial and syringe, wash your hands before beginning. If you take insulin that’s cloudy in appearance after mixing, you’ll need to mix it first. Read the label carefully to ensure you’re properly mixing. Then read on for experts’ top injection tips.

Site Selection

The best place to inject your insulin is in your abdomen—at least 2 inches from the belly button and away from scars and moles. Once in a while, you may choose to use the fatty area on the back of your arm, the middle or outer portion of your thigh, your buttocks, or the top of your upper hip. Rotate your sites, especially if you’re on multiple daily insulin injections. (Head here for tips on injection site rotation, and a diagram of where to inject.) A good rule of thumb is to inject at least 1 centimeter—about the width of your finger—from your last injection site. Constantly injecting insulin in the same spot can cause changes to occur in the skin tissue, which leads to absorption issues:

Lumps
Insulin is a hormone that promotes the growth of fat cells. Continually injecting it into the same spot can cause a ball of fat cells to accumulate through a process known as lipohypertrophy. Don’t inject into these areas; insulin absorption may be impeded.

Indentations
Fat cells may become depleted at the injection site, leading to lipodystrophy. The resulting indentations in the skin may be due to a local allergic reaction to insulin. Insulin isn’t well absorbed in these areas, so avoid injecting there.

Scar Tissue
Injecting repeatedly in the same place may cause scar tissue. Because insulin cannot be absorbed through scar tissue, these sites should not be used for injections.

Illustrations by David Preiss

In a Pinch

You may not need to pinch your skin when injecting insulin. However, if you’re very thin, ask your health care provider if pinching may be useful to avoid injecting into muscle.

Illustrations by David Preiss

Play It Safe

If you’ve lived with diabetes for a while, you may have your own injection preferences and quirks. But it’s important to follow the proper steps.

  • Stay Clean: Wipe the top of your insulin vial or pen with an alcohol swab to keep it clean so you’re not introducing bacteria into the insulin. (No need to prep skin with an alcohol swab, though.)

  • Ban Bubbles: While bubbles won’t harm you, they can take up space in the syringe, preventing you from getting your full dose of insulin. Injecting a full dose is particularly important for people with type 1 diabetes.

  • Nix Needle Reuse: It increases your risk for skin infection; dried insulin in the needle could prevent you from getting your full dose. Needles become dull after they’ve been used, which makes for more painful injections.

Other Injectables

You may be prescribed a GLP-1 receptor agonist to help manage your type 2 diabetes, or a PCSK9 inhibitor to lower your cholesterol. For both of these, you’ll follow the pen instructions on page 39, with a few exceptions.

For instance, you may be taking a GLP-1 receptor agonist only once a week or a PCSK9 inhibitor every two weeks. This means it’s especially important that all the medication is delivered into your body. “If somebody doesn’t do an injection correctly on a once-weekly product, that may affect [their blood glucose for] the entire next week,” says Evan Sisson, PharmD, CDE, MSHA, FAADE, an associate professor at Virginia Commonwealth University School of Pharmacy. Count to 10 before removing the needle from your skin when using a GLP-1, and count to 20 when injecting a PCSK9 inhibitor.