Quick overview of Insulin:

Insulin is a hormone produced in the pancreas.
The pancreas releases insulin to help your body make energy out of sugars (glucose) when you eat.
It also helps you store energy.
Facilitating the movement of glucose out of the bloodstream and into the cells.
As the blood glucose level increases, the insulin level also increases; as the glucose level decreases, insulin release stops.

Insulin’s main function:

Help to transform glucose into energy

Insulin’s main function is to allow other cells to transform glucose into energy throughout your body. Without insulin, cells are starved for energy and must seek an alternate source. This can lead to life-threatening complications.

After a meal, the digestive tract breaks down carbohydrates and changes them into glucose. Glucose is then absorbed into your bloodstream through the lining in your small intestine. Once glucose is in your bloodstream, insulin causes cells throughout your body to absorb the sugar and use it for energy. Insulin also helps balance your blood glucose levels. When there’s too much glucose in your bloodstream, insulin signals your body to store the excess in your liver. The stored glucose isn’t released until your blood glucose levels decrease, such as between meals or when your body is stressed or needs an extra boost of energy.

What is diabetes?

The most common problem associated with insulin is diabetes. Diabetes occurs when the body either does not secrete enough insulin or when the body no longer uses the insulin it secretes effectively.

Diabetes falls into two categories:

Type 1 diabetes (T1D) occurs when the pancreas cannot produce insulin sufficiently to meet its own needs.

The body does not make its own insulin because the insulin-producing cells of the pancreas have been damaged or destroyed. People w/ T1D must administer insulin so that the body can process glucose.

Type 2 diabetes (T2D) is more commonly associated with adults and lifestyle choices. People with type 2 diabetes will produce insulin but often not enough for their body’s needs.

The body does not respond or is resistant to the insulin produced by the pancreas. People with T2D may need to administer insulin to help them better process glucose.

What is the normal range of fasting serum insulin?

Fasting Insulin: < 25 uIU/ml

References:

https://www.endocrineweb.com/conditions/type-1-diabetes/what-insulin
https://www.medicalnewstoday.com/info/diabetes/whatisinsulin.php
https://onedrop.today/2018/04/20/insulin-diabetes-what-is-insulin/
https://www.niddk.nih.gov/health-information/diabetes/overview/insulin-medicines-treatments