Insulin therapy often is an important part of diabetes treatment. It helps keep blood sugar under control and prevents diabetes complications. It works like the hormone insulin that the body usually makes.

Insulin comes from an organ in the stomach area called the pancreas. The main role of insulin is to ensure that sugar from nutrients in food is correctly used or stored in the body.

If your body can make enough insulin, you don't have diabetes. In people who don't have diabetes, insulin helps:

• Control blood sugar levels. After you eat, your body breaks down nutrients called carbohydrates into a sugar called glucose. Glucose is the body's main source of energy. It's also called blood sugar. Blood sugar goes up after you eat.

  When glucose enters the bloodstream, the pancreas responds by making insulin. Then insulin allows glucose to enter the body's cells to give them energy.

• Store extra glucose for energy. After you eat, insulin levels are high. Extra glucose is stored in the liver. This stored glucose is called glycogen.

  Between meals, insulin levels are low. During that time, the liver releases glycogen into the bloodstream in the form of glucose. This keeps blood sugar levels within a narrow range.

If you have diabetes:

Your blood sugar levels keep rising after you eat. That's because there's not enough insulin to move the glucose into your body's cells. With type 1 diabetes, the pancreas stops making insulin. With type 2 diabetes, the pancreas doesn't make enough insulin. And in some people with diabetes, insulin does not work well.

If you don't get treatment for diabetes, high blood sugar can lead to health problems over time. These conditions include:

• Heart attack or stroke.
• Kidney disease leading to kidney failure.
• Eye problems, including blindness.
• Nerve damage with nerve pain or numbness, called diabetic neuropathy.
• Foot problems that may lead to surgery to remove the foot.
• Dental issues.

Insulin therapy keeps your blood sugar within your target range. It helps prevent serious complications.

If you have type 1 diabetes, you need insulin therapy to stay healthy. It replaces the insulin your body doesn't make.

If you have type 2 diabetes, insulin therapy might be part of your treatment. It's needed when healthy-lifestyle changes and other diabetes treatments don't control your blood sugar well enough.

Insulin therapy also is sometimes needed to treat a type of diabetes that happens during pregnancy. This is called gestational diabetes. If you have gestational diabetes, you might need insulin therapy if healthy habits and other diabetes treatments don't help enough.

Any types of insulin help treat diabetes. Each type varies in how quickly and how long it controls blood sugar. You may need to take more than one kind of insulin. Factors that help determine which types of insulin you need and how much you need include:

• The type of diabetes you have.
• Your blood sugar levels.
• How much your blood sugar levels change during the day.
• Your lifestyle.

The main types of insulin therapy include:

• Long-acting, ultralong-acting or intermediate-acting insulins. When you're not eating, your liver releases glucose so your body has energy. Long-, ultralong- or intermediate-acting insulin prevents blood sugar levels from rising without eating.

  Examples of these insulins are glargine (Lantus, Basaglar, others), detemir (Levemir), degludec (Tresiba) and NPH (Humulin N, Novolin N, others). Intermediate-acting insulin lasts about 12 to 18 hours. Long-acting insulin works for about 24 hours. And ultralong-acting insulin lasts about 36 hours or longer.

• Rapid-acting or short-acting insulins. These insulins are ideal for use before meals. If taken with a meal, they can help bring blood sugar back down to the baseline. They also blunt the sugar spikes after you eat. They start to work much faster than long-acting or intermediate-acting insulins do. Sometimes, rapid-acting insulins begin working in as few as 5 to 15 minutes. But they work for a much shorter time. Rapid-acting insulin lasts about 2 to 3 hours. Short-acting insulin lasts about 3 to 6 hours.

  Examples of these insulins include ultrafast-acting aspart (Fiasp) and lispro (Lyumjev); rapid-acting aspart (NovoLog), glulisine (Apidra) and lispro (Humalog, Admelog); and short-acting, regular (Humulin R, Novolin R).

Sometimes, insulin-makers combine two types of insulin. This is called pre-mixed insulin. It can be helpful for people who have trouble using more than one type of insulin. Pre-mixed insulin often starts to work in 5 to 60 minutes. It can keep working for 10 to 16 hours.

Be aware that different preparations of insulin vary in terms of when they start working and how long they last. Be sure to read the instructions that come with your insulin. And follow any directions from your health care team.

Insulin doesn't come in pill form. The digestive system would break the pill down before it had a chance to work. But there are other ways to take insulin. Your health care team can help you decide which method fits best for you.

Choices include:

• Shots or pens. You can inject insulin into the fat just below the skin with a syringe and needle. Or you can inject it with a pen-like device. Both types of devices hold insulin with a needle attached. How often you need to use an insulin pen or shot depends on the type of diabetes you have. It also depends on your blood sugar levels and how often you eat and exercise. You may need to take insulin shots or use insulin pens multiple times a day.
• Insulin pump. An insulin pump gives you small, steady amounts of rapid-acting insulin throughout the day. This works like using a shot of long-acting insulin. A pump also can give a rapid burst of insulin, often taken with food. This works like using a shot of rapid-acting insulin. The pump pushes the insulin into a thin tube placed beneath the skin. Several different kinds of insulin pumps are available.
• Inhaled insulin (Afrezza). This type of insulin is rapid acting. You breathe it in through a device that goes in your mouth, called an inhaler. You take this type of insulin at the start of each meal. People who smoke should not use inhaled insulin. Nor should people who have lung problems such as asthma or chronic obstructive pulmonary disease.

Sometimes, using insulin therapy can be a challenge. But it's an effective way to lower blood sugar. Talk to a member of your health care team if you have any trouble with your insulin routine. Ask for help right away if at-home glucose tests show that you have very low or very high blood sugar. Your insulin or other diabetes medicines may need to be adjusted. With time, you can find an insulin routine that fits your needs and lifestyle. And that can help you lead an active, healthy life.

If you take many doses of insulin a day, ask your health care provider if there's a way to make the routine simpler. Adding noninsulin medicines to your treatment plan might lower the number of insulin shots you need each day. And if you take fewer insulin shots, you'll need to check your blood sugar less often. Certain noninsulin medicines have other health benefits too. Some can help control weight and lower the chances of heart attack or stroke, heart failure, and kidney failure. Some people with type 2 diabetes can stop taking insulin completely after they start taking noninsulin medicines. But it's important to keep taking your insulin as prescribed until your health care provider tells you it's OK to stop.