What is insulin?
Insulin is a hormone made in the pancreas, an organ located behind the stomach. The pancreas contains clusters of cells called islets. Beta cells within the islets make insulin and release it into the blood.
Insulin plays a major role in metabolism—the way the body uses digested food for energy. The digestive tract breaks down carbohydrates—sugars and starches found in many foods—into glucose. Glucose is a form of sugar that enters the bloodstream. With the help of insulin, cells throughout the body absorb glucose and use it for energy.
Insulin's Role in Blood Glucose Control
When blood glucose levels rise after a meal, the pancreas releases insulin into the blood. Insulin and glucose then travel in the blood to cells throughout the body.
- Insulin helps muscle, fat, and liver cells absorb glucose from the bloodstream, lowering blood glucose levels.
- Insulin stimulates the liver and muscle tissue to store excess glucose. The stored form of glucose is called glycogen.
- Insulin also lowers blood glucose levels by reducing glucose production in the liver.
In a healthy person, these functions allow blood glucose and insulin levels to remain in the normal range.
Source: NIDDK (NIH)1
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insulin: Hormone that is produced by the pancreas and regulates the body's energy sources, most notably the sugar glucose.
Source: Australian Institute of Health and Welfare2
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Insulin: A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (Glycogenolysis; Gluconeogenesis) and indirectly by suppressing Glucagon secretion and Lipolysis. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (Diabetes Mellitus, Type 1).3
Types of Insulin
What are the different types of insulin?
Several types of insulin are available. Each type starts to work at a different speed, known as “onset,” and its effects last a different length of time, known as “duration.” 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.
Source: Insulin basics. American Diabetes Association website. Last edited 2015. Accessed August 25, 2016.
Types of Insulin and How They Work
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. Read about financial help for diabetes care.
Source: NIDDK (NIH)4
FAQs about Insulin
What are the different ways to take insulin?
The way you take insulin may depend on your lifestyle, insurance plan, 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. Most people with diabetes use a needle and syringe, pen, or insulin pump. Inhalers, injection ports, and jet injectors are less common.
Needle and syringe
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. Some people with diabetes who take insulin need two to four shots a day to reach their blood glucose targets. Others can take a single shot.
Insulin shots involve drawing insulin from a vial into a syringe and then injecting it under your skin.
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 pen is a convenient way to take insulin
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.
Insulin pumps deliver insulin 24 hours a day.
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. Inhaled insulin is only for adults with type 1 or type 2 diabetes.
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.
Source: NIDDK (NIH)5
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- Source: NIDDK (NIH): niddk.nih.gov/ health-information/ diabetes/ overview/ what-is-diabetes/ prediabetes-insulin-resistance
- Source: Australian Institute of Health and Welfare: aihw.gov.au/ reports-statistics/ health-welfare-overview/ australias-health/ glossary
- Source: MeSH (U.S. National Library of Medicine)
- Source: NIDDK (NIH): niddk.nih.gov/ health-information/ diabetes/ overview/ insulin-medicines-treatments
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Note: This site is for informational purposes only and is not medical advice. See your doctor or other qualified medical professional for all your medical needs.