What Is Insulin?

Insulin is an essential hormone that regulates blood sugar levels in the body. It’s produced naturally in the pancreas. If people don’t make enough insulin or the body doesn’t use insulin effectively, it can lead to high blood sugar levels and diabetes.

What Is Insulin?

Manufactured insulin is a medication that some people with diabetes use to manage their condition.

When we eat, carbohydrates are broken down into glucose, which enters the bloodstream. Insulin works by getting the glucose to go from the blood into the body’s cells to create stores of fat, sugar, and protein.

Insulin also helps us use these stores in order to have energy between meals.

What Conditions Does Insulin Treat?

Insulin is primarily used to manage diabetes. In people with both type 1 and type 2 diabetes, the body’s ability to produce or respond to insulin is impaired, leading to elevated blood sugar levels. For those with type 1 diabetes and some with type 2 diabetes, managing the condition with insulin is essential to avoid complications associated with uncontrolled diabetes.

Conditions Treated by Insulin

• Type 1 Diabetes Type 1 diabetes is an autoimmune condition in which the immune system attacks the cells in the pancreas that make insulin. Because the pancreas produces little or no insulin, it can’t control the amount of sugar in the blood. As a result, people with type 1 diabetes have to use manufactured insulin to manage their disease.
• Type 2 Diabetes People with type 2 diabetes have blood sugar that’s too high because the body doesn’t produce or use insulin normally. Manufactured insulin may be prescribed if lifestyle changes and other medications aren’t enough to control blood sugar levels.
• Gestational Diabetes This is a type of diabetes that can develop during pregnancy. It may require management with insulin to ensure the health of both the mother and the baby. It usually goes away once the baby is delivered.

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• Maturity Onset Diabetes of the Young (MODY) This is an inherited condition in which the beta cells of the pancreas can’t secrete insulin due to a genetic mutation.

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Types of Insulin

There are many different types of insulin available that are delivered through a needle, pen, patch, or pump. There is also an inhalable form of insulin.

Insulin requires a prescription. Your healthcare professional will use factors like age, lifestyle, and risk factors to help determine the appropriate dosage and version of insulin that’s right for you.

Rapid-Acting Insulin

Rapid-acting insulin is used before a meal to prevent your blood glucose from rising and to correct high blood sugars. It can be used with a longer-acting insulin.

Types of rapid-acting insulin include:

• Admelog (Sanofi)
• Apidra (Sanofi)
• Fiasp (Novo Nordisk)
• Humalog (Lilly)
• Lyumjev (Lilly)
• Merilog (Sanofi)
• Novolog (Novo Nordisk)

Regular (Short-Acting) Insulin

Types of regular insulin include:

• Humulin R (Lilly)
• Novolin R (Novo Nordisk)

Intermediate-Acting Insulin

Types of intermediate-acting insulin include:

• Humulin N (Lilly)
• Novolin N (Novo Nordisk)

Long-Acting Insulin

Types of long-acting insulin include:

• Basaglar (Lilly)
• Lantus (Sanofi)
• Levemir (Novo Nordisk)

Ultra-Long-Acting Insulin

The key difference between long-acting insulin and ultra-long-acting insulin is that ultra-long-acting insulin has no peak. This means there is no point in time where there is a maximum effect of insulin in your body, which reduces your risk of having low blood glucose (hypoglycemia). This medication can last up to 36 hours.

• Toujeo (Sanofi)
• Tresiba (Novo Nordisk)

Weekly Insulin

The U.S. Food and Drug Administration (FDA) recently approved a new type of medication that comes as a once-a-week injection. This option may appeal to those who struggle to keep up with daily injections on schedule and those who are considering changing from oral medications to injections.

One weekly injection is currently available:

• Awiqli (Novo Nordisk)

Inhaled Insulin

There is one available inhaled insulin:

• Afreeza (MannKind)

Advanced Delivery Systems and Protocols

Technological advancements are changing how people manage their insulin. These devices represent a significant protocol shift in diabetes management:

• Automated Insulin Delivery (AID) Systems These systems link an insulin pump with a continuous glucose monitoring (CGM) device to automatically adjust insulin delivery rates, a process also known as a “hybrid closed-loop system” or “artificial pancreas.”
• AID Systems for Type 2 Diabetes (T2D) While traditionally used by people with type 1 diabetes, AID systems are now being tested for T2D management, with studies showing significant blood sugar improvements and a low risk of serious side effects.

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   The 2026 American Diabetes Association guidelines recommend AID systems for people with type 1 and type 2 diabetes who are on multiple daily insulin injections.

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• Continuous Glucose Monitoring (CGM) Devices like the Dexcom G8 CGM are being developed with improved accuracy, a smaller sensor size, and future capabilities to detect rising ketones (to help prevent diabetic ketoacidosis) and monitor potassium changes for people with kidney or heart disease.

How Does Insulin Work?

Think of insulin as the key that unlocks your cell’s door so glucose can enter and be used for energy. Without enough insulin, glucose builds up in your blood, leading to high blood sugar and potentially serious conditions like diabetes or diabetic ketoacidosis.

What Are the Possible Side Effects of Insulin?

• Low blood sugar or hypoglycemia
• Weight gain
• Redness, swelling, or itching at the injection site
• Allergic reactions
• Lipodystrophy, or changes to fat tissue at the injection sites, which affects absorption

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Are There Any Risks Related to Insulin?

As with any medication, use of insulin carries some risks. The most common complication of insulin is low blood sugar levels that can result if doses are too high or meals are skipped. Untreated hypoglycemia can cause seizures, coma, and even death.

Other risks, though rare, can include:

• Insulin resistance (with long-term insulin use)
• Low potassium, or hypokalemia

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The Takeaway

• Insulin, a naturally occurring hormone that regulates blood sugar, comes in manufactured forms that are essential for people with type 1 and some type 2 diabetes.
• Types of insulin include rapid-acting, regular, long-acting, and inhaled options, each designed for specific blood sugar control needs.
• Common side effects of insulin include low blood sugar (hypoglycemia), weight gain, and reactions at the injection site.
• Proper insulin management is crucial because incorrect doses or timing can lead to dangerous complications, such as hypoglycemia or insulin resistance.