Insulin is a hormone made in your pancreas, a gland located behind your stomach. Insulin allows your body to use glucose for energy.

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Glucose is a type of sugar found in many carbohydrates. The body processes glucose like this:

  • After a meal or snack, carbohydrates are broken down in your digestive tract and changed into glucose.
  • That glucose is then absorbed into your bloodstream through the lining of your small intestine.
  • Once glucose is in your bloodstream, insulin signals cells throughout your body to absorb the sugar and use it for energy.

Insulin also helps balance your blood glucose levels. When there’s too much glucose in your bloodstream, insulin tells your body to store the leftover glucose in your liver. The stored glucose isn’t released until your blood glucose levels decrease. Your blood glucose levels may decrease between meals or when your body is stressed or needs an extra boost of energy.

Diabetes occurs when your body doesn’t use insulin properly or make enough insulin. There are two main types of diabetes: type 1 and type 2.

Type 1 diabetes is an autoimmune disease, which is a type of disease that causes the body to attack itself. If you’re living with type 1 diabetes, your body cannot make insulin properly. This is because your immune system has harmed the insulin-producing cells in your pancreas. Type 1 diabetes is more commonly diagnosed in young people, although it can develop in adulthood.

In type 2 diabetes, your body has become resistant to the effects of insulin. This means your body needs more insulin to get the same effects. As a result, your body overproduces insulin to keep your blood glucose levels normal. After many years of this overproduction, the insulin-producing cells in your pancreas burn out. Type 2 diabetes can affect people of any age.

Injections of insulin can help manage both types of diabetes. The injected insulin acts as a replacement for, or a supplement to, your body’s natural insulin.

People living with type 1 diabetes can’t make insulin, so they must inject insulin to control their blood glucose levels.

Many people living with type 2 diabetes can manage their blood glucose levels with lifestyle changes and oral medication. However, if these treatments don’t help control glucose levels, people living with type 2 diabetes may also need supplemental insulin.

All types of insulin produce the same effect. They are used to mimic the natural increases and decreases of insulin levels in the body during the day. The makeup of different types of insulin affects how fast and how long they work.

The type of insulin you’ll be prescribed will vary depending on things like:

  • your age
  • your activity level
  • how long it takes your body to absorb insulin
  • how long insulin stays active in your system
Insulin typeOnsetWhen it peaks in your systemDurationWhen taken
Ultra-rapid acting2 to 15 min30-60 min4 hoursTaken with meals, usually with the first bite of a meal.
Commonly used along with long-acting insulin.
Rapid-acting15 min1 hour2 to 4 hoursTaken with meals, typically right before a meal. Commonly used along with longer-acting insulin.
Rapid-acting inhaled10 to 15 min30 min3 hoursTaken with meals, typically right before a meal. Commonly used with injectable long-acting insulin.
Regular or short-acting30 min2 to 3 hours3 to 6 hoursTaken with meals, typically 30 to 60 minutes before a meal.
2 to 4 hours4 to 12 hours12 to 18 hoursTaken once or twice a day. Covers your insulin needs for half a day or overnight. Commonly used with rapid- or short-acting insulin.
Long-acting2 hoursdoesn’t peakup to 24 hoursTaken once a day. Can be used with rapid- or short-acting insulin if needed.
Ulta-long acting6 hoursdoesn’t peak36 hours or moreTaken once a day. Can be used with rapid- or short-acting insulin if needed.
Premixed5 to 60 minvaried peaks10 to 16 hoursTaken twice a day, commonly 10 to 30 minutes before breakfast and dinner. This type is a combination of intermediate- and short-acting insulin.

Talk with a doctor about the right insulin for you and your lifestyle.

Insulin is most commonly administered through a syringe, insulin pen, or insulin pump. The type of insulin injection you use will be based on your personal preference, health needs, and insurance coverage.

Your doctor or diabetes educator will show you how to give yourself the injections. You can inject the insulin under the skin in many different parts of your body, such as your:

  • thighs
  • buttocks
  • upper arms
  • abdomen

Your doctor will likely also explain the importance of changing where on your body you inject insulin to prevent lumps or fatty deposits from forming at the injection site.

Learn more: How to give a subcutaneous injection.

How to choose the right method for injecting insulin

Both syringes and insulin pens use a small needle to inject insulin into your body. There are pros and cons to each, and which one you ultimately end up with will depend on your lifestyle and your doctor’s advice.

Things to know about insulin syringes:

  • They come in a few different sizes.
  • Your doctor will tell you how much insulin you need per dose.
  • You will usually draw the insulin into the syringe when you need it.
  • They’re not as discreet as an insulin pen.

Things to know about insulin pens:

  • Some pens use cartridges that are manually inserted into the pen.
  • Other pens are prefilled and thrown away after all the insulin is used.
  • Needles in pens are often smaller than those in syringes.
  • Not all types of insulin can be used with a pen.
  • Pens can be more expensive than syringes and are sometimes not covered by insurance.

How to take insulin without a syringe

There are two ways to get your insulin without using a syringe or needle. Your doctor will decide if one of these options works for your personal needs.

Insulin pumps:

  • deliver insulin continuously through a plastic tube placed semipermanently into the fatty layer under your skin
  • are typically placed in the stomach area or back of the upper arm
  • can deliver insulin more accurately than a syringe
  • need to be told to deliver additional insulin for meals
  • may cause weight gain
  • may cause infection
  • may be expensive

Insulin inhalers:

  • deliver ultra-rapid-acting insulin
  • are typically used before a meal
  • commonly must be used along with injectable, longer-acting insulin
  • may cause less weight gain
  • may cause coughing
  • don’t give as exact doses compared with other methods
  • require routine testing to monitor for side effects

Like food, insulin doesn’t have a forever shelf life. It’s recommended that you store any insulin you’re not using in the fridge.

However, injecting cold insulin may make the injection feel more painful. Because of this, a best practice is to keep the bottle of insulin you’re currently using in a safe place, away from direct heat and sunlight. Insulin kept at room temperature can last about a month.

Do not store insulin in the freezer, and always check the expiration date before using it.

Side effects from injecting or receiving insulin are rare, but can occur in certain cases. The symptoms of mild allergic reactions are swelling, itching, or redness around the injection area. More severe insulin allergies may include nausea and vomiting.

In either case, talk with your doctor if you notice any of these signs.

Hypoglycemia, or blood glucose levels that are too low, can sometimes occur when you take insulin.

It’s important to balance the insulin that you give yourself with food or calories. If you exercise longer or harder than usual or don’t eat the right amount of calories or carbs, your glucose level can drop too low and trigger low blood sugar. Symptoms of low blood sugar include:

Typically, a blood glucose reading of less than 70 milligrams per deciliter (mg/dL) is considered too low for almost anyone using insulin, but you should talk with your doctor about what is too low for you.

To treat hypoglycemia (less than 70mg/dL or the level your doctor has said is too low for you), carry at least 15 grams of fast-acting carbohydrates with you at all times. That’s about equal to any of the following:

  • 1/2 cup of non-diet soda
  • 1/2 cup of fruit juice
  • 5 Life Saver candies
  • 2 tablespoons of raisins
  • 3 to 4 glucose tablets

People living with type 1 diabetes must use insulin to help control their blood sugar, but those living with type 2 diabetes may be able to use oral medications to help manage their blood sugar instead of injections.

Oral medication is typically prescribed along with lifestyle changes, such as increased activity, weight loss (if applicable), and diet changes.

Medications for type 2 diabetes are designed to lower blood glucose levels, but they may not work for everyone. Typically, they work best for people who have recently developed diabetes and do not use supplemental insulin.

Some medications include:

  • alpha-glucosidase inhibitors
  • bile acid sequestrants
  • biguanides (metformin)
  • DPP-4 inhibitors
  • GLP-1 receptor agonists
  • meglitinides
  • SGLT2 inhibitors
  • sulfonylureas
  • thiazolidinediones (TZDs)

Before prescribing any of these oral medications, your doctor will talk with you about your medical history and any additional medications you take.

If you’re living with type 1 diabetes, your body does not produce insulin, so you’ll need to continue to permanently take insulin.

People living with type 2 diabetes can manage, and maybe even reverse, their diagnosis with lifestyle changes.

According to the Centers for Disease Control and Prevention (CDC), lifestyle changes that can help manage type 2 diabetes are:

  • eating a nutrient-dense diet rich in fruits and vegetables
  • maintaining a moderate weight
  • staying physically active

These lifestyle habits are also helpful for managing type 1 diabetes, but they won’t reverse the diagnosis.

Additionally, you can help manage your blood sugar by:

  • eating at regular times
  • limiting the amount of alcohol you drink
  • trying to quit smoking (if applicable)
  • managing your cholesterol
  • taking your medication as prescribed
  • staying on top of your blood sugar with testing as prescribed

If you’re living with diabetes (type 2 or type 1), taking insulin can help keep your blood glucose level within the recommended range. There are a few ways to take insulin, from syringes, to insulin pens, to an insulin pump, or even with an inhaler.

Maintaining blood glucose levels helps reduce the risk of diabetes complications, such as blindness and the loss of limbs.

In addition to insulin and oral medications, lifestyle changes can help prevent your blood glucose level from getting too high.

Whether you’ve been prescribed insulin or have just recently been diagnosed with diabetes, talk with your doctor about ways to make your treatment as effective as possible.

Read this article in Spanish.