Many people with diabetes need to take insulin to stay healthy. However, insulin therapy can cause a range of side effects.

In this article, we look at what insulin is and who needs to take it. We also cover the side effects, risks, and myths of insulin therapy and provide tips for taking insulin safely.

What is insulin?

Person taking insulin from bottle into syringe
People with diabetes require insulin therapy.

Insulin is a hormone that helps regulate the amount of sugar in the blood.

When a person eats, their digestive system breaks down the food into a simple sugar known as glucose, which raises blood sugar levels. The pancreas responds to this by releasing insulin, which causes sugar to move from the bloodstream into the body’s cells, which need it as an energy source. The body also stores some of the excess sugar in the liver.

Insulin has a counterpart called glucagon, which is a hormone that works in the opposite way. When blood sugar is too low, the pancreas secretes glucagon, which causes the liver to release glucose into the bloodstream.

The body uses insulin and glucagon to ensure that blood sugar levels do not get too high or too low and that cells are getting enough glucose.

Scientists can make synthetic insulin, which doctors use to treat some people with diabetes.

Who needs to take insulin?

Diabetes is a condition that causes high blood sugar levels. There are three main types of diabetes:

  • Type 1 diabetes typically starts in childhood, and people with this condition are unable to produce enough insulin. This form of diabetes usually results from the body’s immune system mistakenly attacking the pancreas, which is where the production of insulin takes place.
  • Type 2 diabetes tends to develop later in life, most commonly affecting people over the age of 45 years. In this form of diabetes, either the pancreas does not produce enough insulin or the body’s cells do not respond to this hormone appropriately.
  • Gestational diabetes occurs during pregnancy and makes it harder for the woman’s body to respond to insulin. Although it typically goes away after giving birth, gestational diabetes increases a woman’s risk of developing type 2 diabetes.

Type 1 and type 2 diabetes are usually lifelong conditions. According to the Centers for Disease Control and Prevention (CDC), more than 30 million people in the United States have diabetes, with type 2 diabetes responsible for around 90 to 95 percent of cases.

People with type 1 diabetes require some form of daily insulin therapy to remain healthy, but the treatment regimen will vary from person to person. Some individuals may need to inject themselves with insulin two to four times a day. Other people may need to use an insulin pump, which is a wearable device that automatically provides insulin throughout the day.

A doctor can help a person with type 1 diabetes find an insulin therapy regimen that suits their needs. According to the American Academy of Family Physicians, there are several different types of insulin that people may use separately or in combination. These include:

  • rapid-acting insulins that start to work within 15 minutes and can last around 3 to 5 hours
  • short-acting insulins that take 30 to 60 minutes to start working and last around 5 to 8 hours
  • intermediate-acting insulins that take between 1 and 3 hours to begin working but last 12 to 16 hours
  • long-acting insulins that start to work in about 1 hour and can last 20 to 26 hours
  • premixed insulins that typically combine a rapid- or short-acting insulin with a longer-lasting insulin

People with type 2 diabetes can often manage their condition without insulin therapy. Alternative treatment options include lifestyle and dietary changes and non-insulin medications, such as metformin. However, if a person is unable to control their blood sugar levels in this way, a doctor may recommend insulin therapy.

Women with gestational diabetes typically receive insulin, but they can also manage their diabetes with metformin.

Side effects and risks of insulin therapy

Potential side effects of insulin therapy include headaches and anxiety
Potential side effects of insulin therapy include headaches and anxiety.

Many different types and brands of insulin are available for use in the U.S. The side effects that a person may experience will depend on the type of insulin that they are taking.

However, some common side effects include:

  • initial weight gain as the body starts to adjust to the therapy
  • blood sugar that drops too low, which is known as hypoglycemia
  • rashes, bumps, or swelling around the injection site
  • headaches
  • upper respiratory infections, such as colds and sore throats
  • anxiety or depression
  • a cough

If a person’s blood sugar drops too low, they may experience symptoms such as:

  • dizziness
  • trouble speaking
  • fatigue
  • confusion
  • pale skin
  • sweating
  • twitching muscles
  • seizure
  • loss of consciousness

There is also the possibility that taking insulin will cause more severe side effects, although these are less common.

A 2013 review compared metformin treatment with insulin therapy in people with type 2 diabetes. The researchers found that the insulin therapy group had an increased risk of a range of complications, including:

Another review concluded that the risks of insulin therapy might outweigh the benefits for people with type 2 diabetes. The authors highlighted the following downsides of the therapy:

  • the need to increase the dose and complexity of the treatment plan over time
  • the increased risk of severe hypoglycemia
  • a potentially higher risk of death
  • a possible increased risk of specific cancers

Myths about insulin therapy

A doctor can offer advice if a person has concerns about insulin therapy.
A doctor can offer advice if a person has concerns about insulin therapy.

According to the American Diabetes Association (ADA), several common myths surround the use of insulin therapy for people with type 2 diabetes. People may sometimes hear others make the following statements, but they are all untrue:

  • needing insulin means that a person failed to manage their condition adequately
  • insulin significantly increases the risk of complications or death
  • insulin causes lasting weight gain
  • insulin therapy does not work
  • insulin is painful to inject
  • insulin is addictive

Tips for taking insulin safely

Insulin is a prescription medication. A person should speak to their doctor about:

  • which type of insulin is right for them
  • possible side effects
  • how to administer insulin safely and effectively

People with type 2 or gestational diabetes should discuss with their doctor whether insulin therapy is the best choice for them. They may be able to use other treatment options to control their blood sugar levels, such as non-insulin medications and lifestyle and dietary changes.

It is essential that people who are taking insulin monitor their blood sugar levels regularly. Taking too much or too little insulin can lead to side effects or complications. It is also vital that a person follows the treatment schedule that they agreed with their doctor and avoids missing doses.

Anyone who experiences side effects from insulin therapy should speak to a doctor. It is possible that another treatment plan or a different type of insulin may be more suitable for their needs and lifestyle. A doctor can also advise on how to prevent or reduce certain side effects.


People with type 1 diabetes need to take insulin daily to control their blood sugar levels and remain healthy. Many individuals with type 2 diabetes and gestational diabetes can use non-insulin medications and dietary and lifestyle changes instead to manage their condition.

When taking insulin, it is vital that people follow their treatment plan. Anyone experiencing side effects or complications from insulin therapy should speak to their doctor, who can recommend other treatment plans or different types of insulin. A doctor can also provide advice on how to prevent or reduce certain side effects.