What is Insulin? What Does it Do?
Insulin is a Hormone Secreted by the Pancreas
Insulin (derived from Latin insula, "island")
is a hormone secreted by cells inside the pancreas
- called islets of Langerhans - which plays a vital role in the
regulation of carbohydrate metabolism. As well as being the body's source
of insulin, the pancreas also produces digestive enzymes and other hormones,
and plays an active part in the metabolism of fat (triglycerides) and
Insulin Helps Regulate Blood Glucose
Insulin is secreted by the pancreas into
the bloodstream in response to an increase in blood sugar, caused by the
metabolism of carbohydrates into glucose after a meal. The circulating
insulin is grabbed by insulin-receptors located on body cells. After grabbing
the insulin, the cell activates other receptors designed to absorb glucose
from the blood stream into the inside of the cell. In this way, the insulin
facilitates the absorption of glucose by the cells, causing a reduction
in blood-glucose levels.
Insulin Sufficiency is Essential for Survival
Adequate insulin is essential. Without
insulin, the body cells (apart from brain cells) cannot properly access
the energy-calories contained in the glucose. Patients with Type 1 diabetes
mellitus depend for their survival on exogenous insulin (meaning
insulin from outside sources), from shots, pens or pumps, because of an
absolute deficiency of the hormone (their pancreas has stopped producing
In comparison, patients with Type 2 diabetes
mellitus have either relatively low insulin production or - more usually
- develop insulin resistance.
In a patient with insulin resistance, the levels of insulin in the blood
are similar to those in normal, non-diabetic individuals. However, the
cells of Type 2 diabetics respond sluggishly to the insulin made by their
pancreas, so their cells cannot properly absorb the circulating blood
glucose. This leads to elevated blood sugar levels requiring medication
(usually) and/or insulin shots (occasionally).
Guide to Insulin Terms
a rapid-acting insulin. On average, aspart insulin starts to lower blood
glucose within 10 to 20 minutes after injection. It has its strongest effect
1 to 3 hours after injection but keeps working for 3 to 5 hours after injection.
a cell that makes insulin. Beta cells are located in the islets of the pancreas.
an extra amount of insulin taken to cover an expected rise in blood glucose,
often related to a meal or snack.
premixed insulin that is 50 percent intermediate-acting (NPH) insulin and
50 percent short-acting (regular) insulin.
very-long-acting insulin. On average, glargine insulin starts to lower blood
glucose levels within 1 hour after injection and keeps working evenly for
24 hours after injection.
a chemical produced in one part of the body and released into the blood
to trigger or regulate particular functions of the body. For example, insulin
is a hormone made in the pancreas that tells other cells when to use glucose
for energy. Synthetic hormones, made for use as medicines, can be the same
or different from those made in the body.
a condition in which the level of insulin in the blood is higher than normal.
Caused by overproduction of insulin by the body. Related to insulin resistance.
implantable insulin pump:
a small pump placed inside the body to deliver insulin in response to remote-control
commands from the user.
an experimental treatment for taking insulin using a portable device that
allows a person to breathe in insulin.
injection site rotation:
changing the places on the body where insulin is injected. Rotation prevents
the formation of lipodystrophies.
places on the body where insulin is usually injected.
a hormone that helps the body use glucose for energy. The beta cells of
the pancreas make insulin. When the body cannot make enough insulin, insulin
is taken by injection or through use of an insulin pump.
a change in the amount of insulin a person with diabetes takes based on
factors such as meal planning, activity, and blood glucose levels.
a device for injecting insulin that looks like a fountain pen and holds
replaceable cartridges of insulin. Also available in disposable form.
an insulin-delivering device about the size of a deck of cards that can
be worn on a belt or kept in a pocket. An insulin pump connects to narrow,
flexible plastic tubing that ends with a needle inserted just under the
skin. Users set the pump to give a steady trickle or basal amount of insulin
continuously throughout the day. Pumps release bolus doses of insulin (several
units at a time) at meals and at times when blood glucose is too high, based
on programming done by the user.
when the level of glucose in the blood is too low (at or below 70 mg/dL).
Also known as hypoglycemia.
areas on the outer part of a cell that allow the cell to bind with insulin
in the blood. When the cell and insulin bind, the cell can take glucose
from the blood and use it for energy.
the body's inability to respond to and use the insulin it produces. Insulin
resistance may be linked to obesity, hypertension, and high levels of fat
in the blood.
a treatment for diabetes in which blood glucose is kept as close to normal
as possible through frequent injections or use of an insulin pump; meal
planning; adjustment of medicines; and exercise based on blood glucose
test results and frequent contact with a person's health care team.
a type of insulin that starts to lower blood glucose within 1 to 2 hours
after injection and has its strongest effect 6 to 12 hours after injection,
depending on the type used. See lente insulin and NPH insulin.
moving the islets from a donor pancreas into a person whose pancreas has
stopped producing insulin. Beta cells in the islets make the insulin that
the body needs for using blood glucose.
groups of cells located in the pancreas that make hormones that help the
body break down and use food. For example, alpha cells make glucagon and
beta cells make insulin. Also called islets of Langerhans.
a device that uses high pressure instead of a needle to propel insulin
through the skin and into the body.
an intermediate-acting insulin. On average, lente insulin starts to lower
blood glucose levels within 1 to 2 hours after injection. It has its strongest
effect 8 to 12 hours after injection but keeps working for 18 to 24 hours
after injection. Also called L insulin.
loss of fat under the skin resulting in small dents. Lipoatrophy may be
caused by repeated injections of insulin in the same spot.
defect in the breaking down or building up of fat below the surface of
the skin, resulting in lumps or small dents in the skin surface. (See
lipohypertrophy or lipoatrophy.) Lipodystrophy may be caused by repeated
injections of insulin in the same spot.
buildup of fat below the surface of the skin, causing lumps. Lipohypertrophy
may be caused by repeated injections of insulin in the same spot.
a rapid-acting insulin. On average, lispro insulin starts to lower blood
glucose within 5 minutes after injection. It has its strongest effect
30 minutes to 1 hour after injection but keeps working for 3 hours after
a type of insulin that starts to lower blood glucose within 4 to 6 hours
after injection and has its strongest effect 10 to 18 hours after injection.
See ultralente insulin.
an intermediate-acting insulin; NPH stands for neutral protamine Hagedorn.
On average, NPH insulin starts to lower blood glucose within 1 to 2 hours
after injection. It has its strongest effect 6 to 10 hours after injection
but keeps working about 10 hours after injection. Also called N insulin.
an organ that makes insulin and enzymes for digestion. The pancreas is
located behind the lower part of the stomach and is about the size of
a commercially produced combination of two different types of insulin.
See 50/50 insulin and 70/30 insulin.
a type of insulin that starts to lower blood glucose within 5 to 10 minutes
after injection and has its strongest effect 30 minutes to 3 hours after
injection, depending on the type used. See aspart insulin and lispro insulin.
short-acting insulin. On average, regular insulin starts to lower blood
glucose within 30 minutes after injection. It has its strongest effect
2 to 5 hours after injection but keeps working 5 to 8 hours after injection.
Also called R insulin.
premixed insulin that is 70 percent intermediate-acting (NPH) insulin
and 30 percent short-acting (regular) insulin.
a container for disposal of used needles and syringes; often made of hard
plastic so that needles cannot poke through.
a type of insulin that starts to lower blood glucose within 30 minutes
after injection and has its strongest effect 2 to 5 hours after injection.
See regular insulin.
long-acting insulin. On average, ultralente insulin starts to lower blood
glucose within 4 to 6 hours after injection. It has its strongest effect
10 to 18 hours after injection but keeps working 24 to 28 hours after
injection. Also called U insulin.
unit of insulin:
the basic measure of insulin. U-100 insulin means 100 units of insulin
per milliliter (mL) or cubic centimeter (cc) of solution. Most insulin
made today in the United States is U-100.
a type of insulin that starts to lower
blood glucose within 1 hour after injection and keeps working evenly for
24 hours after injection. See glargine insulin.