Insulin is a hormone made by the pancreas that helps glucose in your blood enter cells in your muscle, fat, and liver, where it's used for energy. Glucose comes from the food you eat. The liver also makes glucose in times of need, such as when you're fasting. When blood glucose, also called blood sugar, levels rise after you eat, your pancreas releases insulin into the blood. Insulin then lowers blood glucose to keep it in the normal range.
Several types of insulin are available. Each type starts to work at a different speed, and its effects last a different length of time. Most types of insulin reach a peak, which is when they have the strongest effect. Then the effects of the insulin wear off over the next few hours or so.
| Insulin type | How fast it starts to work (onset) | When it peaks | How long it lasts (duration) |
|---|---|---|---|
| Rapid-acting | About 15 minutes after injection | 1 hour | 2 to 4 hours |
| Short-acting, also called regular | Within 30 minutes after injection | 2 to 3 hours | 3 to 6 hours |
| Intermediate-acting | 2 to 4 hours after injection | 4 to 12 hours | 12 to 18 hours |
| Long-acting | Several hours after injection | Does not peak | 24 hours; some last longer |
The chart above gives averages. Follow your doctor's advice on when and how to take your insulin. Your doctor might also recommend premixed insulin, which is a mix of two types of insulin. Some types of insulin cost more than others, so talk with your doctor about your options if you're concerned about cost.
The way you take insulin may depend on your lifestyle and preferences. You may decide that needles are not for you and prefer a different method. Talk with your doctor about the options and which is best for you.
You'll give yourself insulin shots using a needle and syringe. You will draw up your dose of insulin from the vial, or bottle, into the syringe. Insulin works fastest when you inject it in your belly, but you should rotate spots where you inject insulin. Other injection spots include your thigh, buttocks, or upper arm.
An insulin pen looks like a pen but has a needle for its point. Some insulin pens come filled with insulin and are disposable. Others have room for an insulin cartridge that you insert and then replace after use. Insulin pens cost more than needles and syringes but many people find them easier to use.
An insulin pump is a small machine that gives you small, steady doses of insulin throughout the day. You wear one type of pump outside your body on a belt or in a pocket or pouch. The insulin pump connects to a small plastic tube and a very small needle. You insert the needle under your skin and it stays in place for several days. Insulin then pumps from the machine through the tube into your body 24 hours a day. You also can give yourself doses of insulin through the pump at mealtimes. Another type of pump has no tubes and attaches directly to your skin, such as a self-adhesive pod.
Another way to take insulin is by breathing powdered insulin from an inhaler device into your mouth. The insulin goes into your lungs and moves quickly into your blood.
An injection port has a short tube that you insert into the tissue beneath your skin. On the skin's surface, an adhesive patch or dressing holds the port in place. You inject insulin through the port with a needle and syringe or an insulin pen. The port stays in place for a few days, and then you replace the port. With an injection port, you no longer puncture your skin for each shot - only when you apply a new port.
This device sends a fine spray of insulin into the skin at high pressure instead of using a needle to deliver the insulin.
