Insulin is a hormone that is naturally produced in the body by your pancreas. Insulin is how the human body regulates blood glucose levels. In a non-diabetic person, the body automatically detects how many carbohydrates are eaten and releases the proper amount of insulin to compensate. There are two types of insulin, basil or background insulin and bolus or fast acting insulin. Basil insulin is a long lasting background insulin that regulates your body all day. Bolus is fast acting and controls carbohydrates as they are consumed. The insulin that is used today is harvested from the pancreas of a pig and then purified for human use.
There are two ways that insulin is normally given to a diabetic. This first is subcutaneous injection or shots. Bolus insulin shots are given at every meal and the dose has to be calculated based on the current Blood Glucose levels as well as carbs consumed. Basil insulin is injected once to twice daily. The second way a diabetic get insulin is through an insulin pump. An insulin pump uses a catheter that is placed just under the patient’s skin and secrets the insulin. It gives the basil dose by slowly releasing small amounts of insulin throughout the day. At meals the bolus dose is given by using the controls on the pump to instruct it on how much to release.
Below are some videos I found on the history of insulin.