What is insulin, and how does it work (mechanism of action)?

  • Insulin is a naturally-occurring hormone secreted by the pancreas. Insulin is required by the cells of the body in order for them to remove and use glucose from the blood. Cells use glucose to produce energy that they need to carry out their functions. Researchers first gave an active extract of the pancreas containing insulin to a young diabetic patient in 1922, and the FDA first approved insulin in 1939. Currently, insulin used for treatment is derived from beef and pork pancreas as well as recombinant (man-made) technology. The first recombinant human insulin was approved by the FDA in 1982.
  • People with diabetes mellitus have a reduced ability to take up and use glucose from the blood, and, as a result, the glucose level in the blood rises. In type 1 diabetes, the pancreas cannot produce enough insulin. Therefore, insulin therapy is needed. In type 2 diabetes, patients produce insulin, but cells throughout the body do not respond normally to the insulin. Nevertheless, insulin also may be used in type 2 diabetes to overcome the resistance of the cells to insulin. By increasing the uptake of glucose by cells and reducing the concentration of glucose in the blood, insulin prevents or reduces the long-term complications of diabetes, including damage to the blood vessels, eyes, kidneys, and nerves. Insulin is administered by injection under the skin (subcutaneously). The subcutaneous tissue of the abdomen is preferred because absorption of the insulin is more consistent from this location than subcutaneous tissues in other locations.

What brand names are available for insulin?


Do I need a prescription for insulin?

Yes; No (regular and NPH insulin)

What are the uses for insulin?

Insulin is prescribed for the treatment of type 1 and type 2 diabetes mellitus.

What are the side effects of insulin?

Hypoglycemia is the most common side effect that may occur during insulin therapy. Symptoms of hypoglycemia include:

Patients may experience blurred vision if they have had elevated blood sugar levels for a prolonged period of time and then have the elevated levels rapidly brought to normal. This is due to a shift of fluid within the lens of the eye. Over time, vision returns to normal. Other side effects that may occur include headaches, skin reactions (redness, swelling, itching or rash at the site of injection), worsening of diabetic retinopathy, changes in the distribution of body fat (lipodystrophy), allergic reactions, sodium retention, and general body swelling. Insulin causes weight gain and may reduce potassium blood levels. In addition to these side effects, inhaled insulin (Afrezza) may cause throat pain or irritation and cough and patients should inform their healthcare professional of any unresolved symptoms affecting the lungs for follow up.

What is the dosage for insulin?

The abdomen is the preferred site for insulin injection, but the sites of injection must be rotated in order to prevent erosion of the fat beneath the skin, a condition called lipodystrophy. Dosing is adjusted for each patient. A combination of short acting/rapid acting and intermediate insulin or long acting insulin are typically used.


Diabetes is defined best as... See Answer

Is insulin safe to take if I'm pregnant or breastfeeding?

  • Insulin is the drug of choice for controlling diabetes during pregnancy, that is, it is preferred over oral drugs to reduce blood sugar. NPH, insulin aspart, insulin detemir, and insulin lispro also are used during pregnancy.
  • Insulins are considered safe to use by nursing mothers.

What else should I know about insulin?

How should I keep insulin stored?

  • Unopened insulin should be stored between 2 C and 8 C (36 F and 46 F); it should not be placed in a freezer.
  • Insulin vials that are being used can be kept at room temperature for up to a month.
  • All vials should be protected from sunlight and excessive heat.
  • Unused insulin should be thrown away after the expiration date.
  • The vials should never be shaken.


Insulin is a medication prescribed to treat type 1 diabetes and type 2 diabetes mellitus. There are several types, preparations, and dosage amounts of insulin. Side effects include nausea, hunger, headache, blurred vision, irritability, heart palpitations, and tremors. Review drug interactions, dosage, and pregnancy and breastfeeding safety information prior to taking insulin.

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Medically Reviewed on 7/1/2019
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