Insulin is a lifesaving medicine in diabetes, but it has to get under the skin to work. For 100 years, most patients have taken insulin with a syringe and needle, drawing their dose from a vial and injecting it through their skin, which can be difficult. The newer insulin pens have made the injection process easier and less painful, but pens have their own learning curve.
Insulin injection technique: tips and tricks
Self-injection can be harder than it sounds. People may experience bruising or scarring at injection sites, give themselves incorrect doses, or inject in ways that lead to poor uptake of insulin in the body. They may find the process scary and uncomfortable. Here are some common mistakes that make it harder and some ways to make it easier.
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Injection depth
Insulin absorbs best from the fatty tissue under the skin (“subcutaneous fat”). If the needle goes too deep, the insulin may get into muscle tissue or a small blood vessel and cause bruising and pain. Avoid this by pinching up a fold of tissue (usually on the abdomen) and pushing the needle straight in, not at a slant. 
If you’re using a syringe, you need the right size needle. Thicker needles let insulin in faster, but thinner needles hurt less. Shorter needles lower the risk of going too deep. Insulin needle length varies from 4 to 6 millimeters, and shorter is usually better. Ask your doctor, diabetes educator or pharmacist to help choose your best-size needle and syringe. Insulin pens also come with a choice of needle sizes.
Injection site rotation
Injection sites should be changed with each injection, a strategy known as injection site rotation. Injecting repeatedly into the same site can cause scarring, swelling and poor absorption. Each new site should be at least one inch from the previous site.
One good way is to set up an imaginary clock on your abdomen, with your belly button in the middle. Give your first dose at “12,” meaning at least one inch above the belly button. Subsequent doses should move around the clock. All sites should be at least an inch away from the belly button, and one should not inject into an area of scarring or bruising. The upper thighs are another safe site for injection.
Injection speed
If you pull a syringe or pen out too quickly, you may not get your full dose. If injecting with a syringe, hold it in place for five seconds after pushing the plunger all the way in. With an insulin pen, hold for ten seconds, because the injection itself takes longer. Your skin should not be wet afterward. Do not rub the site after removing the needle.
Safe insulin storage
Insulin should be kept refrigerated before opening, but at room temperature after opening (the opposite of food). You don’t want to inject cold medicine. When starting a new vial or a new pen from the fridge, take it out long enough to reach room temperature, usually at least 30 minutes before using.
Do not let insulin freeze (so don’t store it in the back of the fridge near the cooling tube), and do not keep it in direct sunlight or in a car where it might get too warm. After freezing or heating, insulin will not work well.
Insulin is good for 28 days at room temperature, so mark that date on a calendar and replace your vial, pen or cartridge after 28 unrefrigerated days.
Insulin organization
Many patients inject two insulins: a long-acting basal, along with a short-acting bolus to cover meals. You don’t want to confuse them. Most educators advise keeping different insulins in different places — for instance, keeping the basal insulin in your bedroom and the bolus in the kitchen, near where you’ll use them.
Insulin labels
Insulin has a “use-by” date. Check dates when taking out a new vial, a new pen or a cartridge. Additionally, make sure it’s the right type of insulin and that it looks like your insulin usually looks, because pharmacies can make mistakes. Also, insulin should never be discolored.
Priming insulin devices
Insulin pens need to be “primed,” meaning getting the air our of the cartridge and needle. After putting on a new needle, hold the syringe needle-up and tap the cartridge a few times to get any air to rise to the top. Then set the dose dial to 2 units and push the inject button. You should see a drop of insulin on the needle tip. If you don’t see a drop, try it again, so that you’re not injecting air.
With a syringe and vial, pull back the syringe plunger to inject as much air into the vial as the insulin you will withdraw. Then insert the needle into the vial and, turning the insulin and syringe upside down, push the air in. Making sure the needle is submerged in the liquid, withdraw your insulin dose. Then push the insulin back into the vial and withdraw again.
Mixing insulin
Insulin comes in many forms, some of which contain the cloudy NPH insulin and need to be gently mixed. Never shake an insulin cartridge or vial — that may cause insulin to clump up and not absorb. Instead, gently rotate the vial, syringe or cartridge between your hands ten times. Then turn it over end to end ten times. It should be thoroughly mixed by then. To avoid shaking in storage, don’t keep cartridges or vials on the refrigerator door, where they may get jostled when the door opens and closes.
Dexterity and vision concerns
Injecting insulin requires some strength and dexterity in one’s hands and the ability to see the syringe, pen or vial. Pens are easier to use than syringes, but still require some hand and eye function. There are syringe magnifiers and tactile measurement devices for low-vision people, but it’s important to work with a doctor or educator to get equipment you can use well. Insulin pens require dialing the dose by hand, so patients need to check that they can see the numbers and turn the dial.
Insulin injection technique: Learn and practice
As with learning anything new, the keys to insulin injection success are training and practice. Ask your doctor or educator to show you how it’s done, and to guide you through doing it yourself. There are also training devices you can take home to practice with. Studies show that people who practice injecting are much more likely to do it right and to keep doing it.
Take the doctor’s informational handouts, and also watch videos of insulin injections. You can find videos on YouTube for injecting with an insulin pen and with a syringe. You can do this.
Want to learn more about insulin? Read “What Does Insulin Do?” then watch “Injecting Insulin.”
