What is the function of insulin in the medical field?

October 11, 2025 •

4 min read

An estimated 589 million adults worldwide were living with diabetes in 2024, a condition where the body's relationship with insulin is impaired [1.10.2]. Medically, what is the function of insulin in the medical field? It is a life-saving hormone therapy that regulates blood glucose, preventing serious long-term complications [1.2.4].

Quick Summary

Insulin's primary medical function is to manage blood sugar in diabetes by replacing or supplementing the body's natural supply, enabling cells to use glucose for energy and preventing hyperglycemia.

Key Points

Primary Function: Insulin's main medical role is to manage blood glucose in people with Type 1, Type 2, and gestational diabetes by helping cells absorb sugar for energy [1.2.3].
Life-Saving for Type 1 Diabetes: For individuals with Type 1 diabetes, whose bodies produce no insulin, daily insulin therapy is essential for survival [1.4.2].
Variety of Formulations: Medical insulin comes in different types—from rapid-acting to long-acting—which are often combined to mimic the body's natural insulin patterns [1.4.3].
Multiple Administration Methods: Insulin is administered via injections (syringe or pen), insulin pumps, or inhalation, as it cannot be taken orally [1.4.3].
Treats Hyperkalemia: In emergencies, insulin is used intravenously with glucose to rapidly lower dangerously high blood potassium levels [1.3.3, 1.7.4].
Diagnostic Tool: The Insulin Tolerance Test uses controlled hypoglycemia to evaluate the function of the pituitary and adrenal glands [1.7.1].
Critical Care Management: Insulin is used in ICUs to manage stress-induced hyperglycemia in critically ill patients, reducing mortality and complications [1.7.1].
Main Side Effect: The most common and significant risk of insulin therapy is hypoglycemia (low blood sugar), which requires careful management [1.8.2].

The Fundamental Role of Insulin

Insulin is a hormone produced by the beta cells within the pancreas [1.2.1]. Its primary physiological function is to regulate glucose metabolism, ensuring that the body's cells get the energy they need from the food we eat [1.2.5]. When you consume carbohydrates, your body breaks them down into glucose, a type of sugar that enters your bloodstream [1.2.1, 1.2.2]. This rise in blood glucose signals the pancreas to release insulin. Insulin then acts like a key, allowing glucose to move from the blood into body tissues like muscle and fat to be used for energy or stored as glycogen in the liver for later use [1.2.2, 1.3.3]. This process is crucial for maintaining stable blood sugar levels [1.3.1].

The Primary Medical Application: Diabetes Management

The most prominent function of insulin in the medical field is the treatment of diabetes mellitus. In people with diabetes, this regulatory system is broken. This can be due to the body not producing enough insulin, not being able to use the insulin it produces effectively (insulin resistance), or both [1.2.2]. Without effective insulin action, glucose builds up in the bloodstream, a condition known as hyperglycemia, which can lead to severe long-term health complications, including heart disease, stroke, kidney failure, nerve damage, and eye problems [1.2.3, 1.4.1].

Treating Different Types of Diabetes

Type 1 Diabetes: This is an autoimmune condition where the body's immune system destroys the insulin-producing beta cells in the pancreas [1.3.1]. As a result, the body produces little to no insulin. For individuals with Type 1 diabetes, daily insulin therapy is not just a treatment but a necessity for survival [1.4.2].
Type 2 Diabetes: In this more common form, the body either doesn't produce enough insulin or the body's cells become resistant to insulin's effects [1.4.3]. While lifestyle changes and oral medications are often the first line of treatment, many people with Type 2 diabetes eventually require insulin therapy to maintain target blood sugar levels when other treatments are no longer sufficient [1.2.1, 1.4.1].
Gestational Diabetes: This type of diabetes occurs during pregnancy. If diet and exercise are not enough to control blood sugar levels, insulin therapy may be prescribed to protect both the mother and the baby from complications [1.4.1].

Types of Medical Insulin

Insulin therapies are categorized by how quickly they work, when they peak, and how long they last. A patient's regimen may involve more than one type to mimic the body's natural insulin release [1.4.3].


Insulin Type	Onset of Action	Peak Time	Duration
Rapid-Acting	5-15 minutes	1-2 hours	2-4 hours	[1.5.2]
Short-Acting	30 minutes	2-3 hours	3-6 hours	[1.5.2]
Intermediate-Acting	2-4 hours	4-12 hours	12-18 hours	[1.5.2]
Long-Acting	2 hours	No peak (or minimal)	Up to 24 hours	[1.5.2]
Ultra Long-Acting	6 hours	No peak	36 hours or longer	[1.5.2]
Premixed	5-60 minutes	Varies (dual peaks)	10-16 hours	[1.5.2]

Methods of Administration

Because insulin is a protein that would be destroyed by stomach acid, it cannot be taken orally [1.4.3]. The most common administration methods include:

Syringes and Vials: The traditional method, involving drawing a dose from a vial into a syringe for injection [1.6.1].
Insulin Pens: These devices contain a prefilled cartridge of insulin and use fine, short needles, making them more convenient and discreet than syringes [1.6.2].
Insulin Pumps: A small, computerized device worn on the body that delivers a continuous, steady amount of rapid-acting insulin (basal rate) through a thin tube inserted under the skin. Users can also program it to deliver a larger dose (bolus) at mealtimes [1.4.4, 1.6.2].
Inhaled Insulin: A rapid-acting insulin powder that is inhaled through the mouth at the beginning of a meal [1.2.4].

Other Medical Functions of Insulin

Beyond diabetes, insulin has several other important, albeit less common, medical applications.

Treatment of Hyperkalemia: In emergency settings, an intravenous solution of glucose and insulin is used to treat dangerously high potassium levels (hyperkalemia). Insulin helps to drive potassium from the bloodstream into the cells, temporarily lowering blood potassium levels [1.3.3, 1.7.4].
Diagnostic Testing: The Insulin Tolerance Test (ITT) uses an injection of insulin to induce hypoglycemia (low blood sugar). This stress response is used to assess the function of the hypothalamic-pituitary-adrenal (HPA) axis and growth hormone production [1.7.1, 1.7.3].
Critical Care: In intensive care units (ICUs), insulin infusions are used to manage stress-induced hyperglycemia in critically ill patients, even those without a history of diabetes. Controlling blood sugar in this setting has been shown to reduce mortality and complications like sepsis and organ failure [1.7.1].
Parenteral Nutrition: Regular human insulin is often added to total parenteral nutrition (TPN) solutions to control the hyperglycemia that can result from intravenous feeding [1.7.1].

Potential Side Effects and Conclusion

The most common and serious side effect of insulin therapy is hypoglycemia (low blood sugar), which can occur if too much insulin is taken, a meal is skipped, or from more exercise than usual [1.8.2]. Symptoms include sweating, shakiness, confusion, and dizziness [1.8.3]. Other potential side effects include weight gain and skin reactions at the injection site (lipodystrophy) [1.8.1, 1.8.4].

In conclusion, the function of insulin in the medical field is multifaceted and life-saving. Its discovery in the 1920s transformed Type 1 diabetes from a fatal disease into a manageable condition [1.11.2]. Today, it remains the cornerstone of diabetes management, preventing devastating complications and allowing millions to lead healthier lives. Its applications in critical care and diagnostics further underscore its importance as a powerful therapeutic and diagnostic tool in modern medicine.

For further information, consult authoritative sources such as the American Diabetes Association.

Frequently Asked Questions

Insulin is a protein-based hormone. If it were taken orally as a pill, the acid in the stomach would break it down and digest it before it could enter the bloodstream to do its job, rendering it ineffective [1.4.3, 1.6.5].

In Type 1 diabetes, the pancreas stops making insulin altogether due to an autoimmune attack [1.4.1]. In Type 2 diabetes, the body either doesn't produce enough insulin or becomes resistant to the insulin it does make [1.2.2].

No, not everyone with Type 2 diabetes needs insulin. Many can manage their blood sugar through lifestyle changes like diet and exercise, and oral medications. Insulin therapy is typically introduced when these measures are no longer sufficient to control blood glucose levels [1.2.1, 1.4.1].

The most common side effect of insulin therapy is hypoglycemia, which is a state of low blood sugar [1.8.2]. This can happen if the dose is too high for your needs, you skip a meal, or you exercise more than planned.

Insulin has several non-diabetic uses, most notably the emergency treatment of hyperkalemia (high blood potassium), where it helps move potassium from the blood into cells. It is also used in diagnostic tests for hormone deficiencies and to manage blood sugar in critically ill patients in the ICU [1.7.1].

Repeatedly injecting insulin in the same spot can cause a condition called lipodystrophy, which involves the formation of hard lumps or fatty deposits. This can be unsightly and can affect how the insulin is absorbed, making it less effective. It is important to rotate injection sites [1.8.3, 1.8.4].

Unopened vials and pens of insulin should generally be stored in the refrigerator. Once in use, a vial or pen can often be kept at room temperature for a set period (usually around 28 days), away from direct heat and light. Never freeze insulin [1.8.1, 1.9.2].