Insulin is a necessary part of the treatment plan for all people with Type 1 diabetes and many with Type 2. Insulin helps get glucose from the bloodstream into the muscle and fat cells to be used for fuel. It cannot be taken as a pill or a swallowed liquid, because it would be broken down by the digestive system before it reached the bloodstream, where insulin does its work. Instead, insulin is injected or infused into the fatty tissue under the skin.
There are a number of devices that can be used to deliver insulin, including syringes, insulin pens, jet injectors, and insulin pumps. No single device or type of device works well for everyone. The decision of which to use may be based on a person’s insulin regimen, ability to manipulate or operate a particular device, visual ability, insurance coverage or ability to afford a particular device and related supplies, occupation, and daily schedule or leisure-time activities. Discussing your needs and preferences with your diabetes care team is the best way to pick the device that will work well for you and get the training you need to use it correctly.
The most common method of insulin delivery in the United States is by syringe. Medical syringes are relatively small, are disposable, and have fine needles with special coatings that make injecting as easy and painless as possible. To take insulin with a syringe, the user first pulls back on the plunger to draw in air equal to the amount of insulin to be drawn, inserts the syringe needle into a vial of insulin, pushes the air into the vial, pulls back on the plunger until the correct dose is drawn into the syringe barrel, then inserts the needle through the skin and presses down on the plunger until the barrel is emptied.
People who have difficulty drawing up insulin doses on their own may be able to have a caregiver draw up doses in advance and store the filled syringes in the refrigerator with the needles pointing upward until needed. (Placing the needles in a small cup will keep them upright.) If you use this option, be sure to discuss with your diabetes care team how far in advance syringes can be filled.
Syringes come in a variety of sizes, with different-size barrels, different needle gauges (thicknesses), and different needle lengths. The higher the gauge, the finer (thinner) the needle. Your diabetes care team will help choose the appropriate syringe for you based on the sizes of your insulin doses and your personal preference for needle gauge and length. While some people may prefer a shorter needle, insulin leakage at the injection site or worsening blood glucose control are signs that a longer needle may be necessary to deliver the insulin properly.
Reusing syringes is not recommended due to potential complications such as more painful injections as the needle dulls with use, infection, or tissue damage. The best practice is to use a new syringe for each injection.
If you travel outside of the United States, it is important to be aware that insulin is manufactured in different strengths; however, U-100 (100 units of insulin per milliliter [ml] of fluid) is the most common strength. The syringes for administering insulin are specifically designed for each different strength. Therefore, a U-100 syringe should normally only be used with U-100 insulin. All insulin syringes in the United States are designed for use with U-100 insulin.
While most insulin sold in the United States is U-100, people who are severely insulin resistant may use U-500 (500 units of insulin per ml). However, no U-500 syringes are manufactured, so people who are prescribed U-500 insulin must work with their diabetes care team to learn how to draw up the correct dose in a U-100 syringe.