Introduction to Insulin

Insulin is a drug most associated with diabetes and has proven to be a miracle drug for persons with diabetes. Improvements in insulin are made on a regular basis as new types arrive on the market and combinations of insulin and medication are blended into one injection.  At some time in the future, some of these insulins will be used in a closed-loop system where a continuous glucose meter and an insulin pump can communicate with each other and act like the pancreas in the body which is responsible for insulin secretion and normalization of glucose in the bloodstream.

History of insulin

Insulin was first discovered in 1921, 100 years ago, by a young orthopedic surgeon, Frederick Banting, and his assistant, Charles Best.   In January 1922, a 14-year-old boy dying from diabetes in a Canadian hospital became the first person to receive an insulin injection. Within 24 hours, Leonard’s dangerously high blood glucose levels dropped to near-normal levels.  He lived a healthy life for 13 years dying of pneumonia at 26 years of age.  Insulin initially came from pigs (Novo Nordisk) and cattle (Eli Lilly and company).  In 1978 the first human, manmade insulin was synthesized by David Goeddel and his colleagues.  Only synthesized insulin is used today as they are less allergenic than animal insulins.

What is insulin

Insulin is a hormone produced by the Beta cells and stored in the pancreas; it is secreted into the bloodstream when the body senses the intake of food and begins to work when it encounters glucose or sugar from the food that is eaten.  Insulin can be endogenous or made by the body or insulin can be exogenous or manufactured. Individuals with diabetes may no longer make any insulin, make insufficient insulin, or can no longer use the insulin that is made.   Because of the different kinds of insulin, it can be administered by syringe, pen, or pump.

Insulin Vial & Syringes

Insulin Pen

Insulin Pump

How does insulin work

how does insulin workInsulin acts as a key, opening the channels of the cells of the body to allow the glucose in the bloodstream to enter such cells and be used as energy.

What does insulin do:

  • Allows the cells throughout the body to use glucose for energy
  • Permits glucose uptake by cells in skeletal muscle for physical activity
  • Enables the release of glucose to fuel the brain and nervous system; vital for cognitive activity
  • Keeps glucose in the body at a healthy level and prevents high blood sugar (hyperglycemia) or low blood sugar (hypoglycemia)
  • Stimulates the entry of amino acids (the body’s building blocks) into the cell to promote the protein building necessary for the cell structure and function
  • Enhances fat storage for future use as energy; prevents fat from being used as energy unless needed
  • Promotes the storage of glucose in the liver and muscles as a future energy source; this is called glycogen
  • Prevents the liver from making more glucose when it is not needed.

All of these are primary functions of insulin that are disrupted in the person with diabetes

how our body uses amino acids

Role of insulin in other parts of the body:

  • Promotes increased activity in brain regions associated with learning and memory
  • Controls fluid and sodium levels through excretion in the urine
  • Allows potassium into cells; potassium is important for fluid balance, muscle contraction, and nerve signals.
  • Promotes muscle repair after sickness or injury
  • Converts lipids, a kind of fat, into triglycerides.  Triglycerides can be a source of energy, but a high level of triglycerides can contribute to heart disease.


How is insulin used:

  • Type 1 Diabetes – Persons with Type 1 Diabetes need an external or exogenous source of insulin to live.  They may have a brief “honeymoon” period where their pancreas still produces insulin but generally that is short-lived.
  • Type 2 Diabetes – Many persons wi