Blood Glucose

Insulin Facts

January 11, 2017   /

Insulin is a hormone that is produced by the beta cells of the pancreas. When you eat, insulin is released to move glucose into the cells for use or storage.

In people with type 1 diabetes, the pancreas does not make insulin. All people with type 1 diabetes must give themselves insulin injections.

In people with type 2 diabetes, the cells do not respond to the insulin that is produced and/or enough insulin is not produced. Eventually, in type 2 diabetes, the beta cells become fatigued and will stop responding to oral medications the way that they initially did. This is the natural progression of diabetes. At this point, these people must start using insulin injections to control their blood glucose levels.

People with diabetes have used insulin for more than 80 years. Without the proper amount or response to insulin, glucose builds up in the blood and is excreted in the urine. Thus, the body loses its main source of energy. Too much glucose in the bloodstream can damage the blood vessels and nerves, potentially leading to very serious and sometimes life-threatening conditions.

Insulin storage
You can keep insulin that you will use in the very near future at room temperature. Store insulin that you will use later in the refrigerator. Take the insulin that you will use the next day out of the refrigerator the night before. Never keep insulin in a hot place, such as in your car during warm months, or where it will become frozen. It is not recommended that you keep your insulin in a handbag or briefcase. Shaking insulin can create air bubbles that will affect the amount of insulin you withdraw.

Types of insulin
Four main types of insulin are available. They are different from each other in how long they take to become effective and how long of a period of time that they will remain effective. The time between your insulin injection and mealtime will differ based on which type of insulin you are prescribed. For example, intermediate-acting insulin usually is taken about 30 minutes before meals. Once you have taken your insulin, it is important to eat at the recommended time to avoid hypoglycemia (low blood glucose).


  • Rapid-acting insulin starts to work 5 minutes after it is injected and keeps working for 2–4 hours
  • Short-acting insulin starts to work within 30 minutes and keeps working for 3–6 hours
  • Intermediate-acting insulin starts to work within 2–4 hours and keeps working for 12–18 hours
  • Long-acting insulin starts to work within 6–10 hours and keeps working for 20–24 hours

In addition to these types of insulin, premixed combinations of intermediate- and rapid-acting insulin also are available.

Side effects to using insulin
People who take insulin often gain weight. This is possibly because of a few things. If individuals are becoming hypoglycemic too often and needing to eat to normalize their blood glucose frequently, this could lead to weight gain. People who use insulin sometimes gain small amounts of weight because they are able to better utilize the food they eat. Lastly, before beginning to use insulin, some individuals are dehydrated, which can make it appear that they have gained weight, when actually they are just no longer dehydrated.

Insulin also can lead to hypoglycemia (low blood glucose), if the dosage is not correct. If your blood glucose drops to 70 or below, contact your physician.

It is important to keep detailed records of:

  • What and when you eat
  • What medications you take
  • How much insulin you use
  • The times that you take medications and insulin
  • Your blood glucose levels

Exogenous insulin
Almost inevitably, a person with type 2 diabetes will stop creating their own insulin with time and will require exogenous insulin. A study published in the May 24, 2008, issue of Lancet found that when people diagnosed with type 2 diabetes were started on insulin therapy right away, they had better blood glucose control than people who were started on oral medication.

If you are using insulin, this does not mean that you have failed or messed up in any way. This is a common misconception and can lead to a substantial amount of unnecessary guilt among people with diabetes. If you have type 2 diabetes, even if you follow the diet perfectly, exercise often, and are compliant with all of your medications, eventually you will likely need insulin. Another common misconception is that only people with “really bad” diabetes need insulin. Diabetes is a serious condition whether you control it with insulin, oral medications, or diet and exercise.

Diet and insulin
Your doctor or other diabetes specialist will prescribe a certain number of insulin units to cover the carbohydrates that you eat. This is a very individualized formula. However, you still cannot eat whatever you want. Eating a poor diet can lead to, among other things, high blood pressure, high cholesterol, and weight gain.

People with diabetes are at an increased risk for developing heart disease, so it is important to take preventive measures. Furthermore, using extra insulin to cover large meals increases the chances of developing hypoglycemia, which sometimes becomes quite dangerous.

References and recommended readings
American Diabetes Association®. Insulin basics. Available at: Accessed June 20, 2012.

California Diabetes Program. Myths and facts about insulin. Available at: Accessed June 20, 2012.  

University of Washington School of Medicine, Dept of Obstetrics and Gynecology, Diabetes in Pregnancy Program. Some common questions about insulin. Available at: Accessed June 20, 2012.