Where Insulin Comes From
Almost all of the insulin sold in the United States today is what is known as "human insulin." Developed by scientists, this laboratory-created insulin is made by DNA recombinant technology and is very similar, really identical, to insulin from a human pancreas. It's available in varieties that are designed to start working within just a few minutes or last for many hours, giving insulin users a lot of control over their blood sugar levels. (Before the introduction of human insulins, people used insulin from beef and pork sources.)
Insulin can't be taken as a pill or capsule because the digestive juices in the stomach ruin its effectiveness. Oral insulin pills might be a reality someday, but right now the only way to take insulin is by injecting it directly into the layer of fat just below the skin. Most people inject insulin with a syringe or insulin pen, although other methods are available.
Insulin Strengths: U-40 and U-100
In the United States, insulin is labeled "U-100," which means there are 100 units of insulin per milliliter of fluid in the vial. Some insulin is also available in U-500 strength. This form of insulin is only for people with marked insulin resistance who take doses of more than 200 units per day.
U-100 insulin syringes have orange caps
U-40 insulin syringes have red caps
Basal and Bolus Insulins
The pancreas naturally secretes insulin in two different ways:
While people with type 1 diabetes need a treatment program that gives them both basal and bolus insulin, the treatment for people with type 2 varies and usually changes over time:
Injections of rapid-acting and short-acting insulins provide the bolus insulin supply needed after meals. Conversely, injections of intermediate-acting and long-acting insulin mimic the body's natural basal supply.