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Insulin is used to treat people who have
diabetes. Each type of insulin acts over a specific
amount of time. The amount of time can be affected by exercise, diet, illness,
some medicines, stress, the dose, and where the insulin has been injected.
Insulin strength is usually U-100, or 100 units of insulin in one milliliter of fluid. Short-acting (regular) insulin is also available in U-500, or 500 units of insulin in one milliliter of fluid. This is five times more concentrated than U-100 regular insulin.
Insulin is made by different companies. Make sure you use the same type of
starts to work (onset)
of greatest effect (peak)
How long it lasts
Humulin R, Novolin R (insulin regular)
Humulin N, Novolin N (insulin
Up to 24 hours
Rapid-acting insulins work over a
narrow, more predictable range of time. Because they work quickly, they are used most often at the start of a meal. Rapid-acting insulin acts most like insulin
that is produced by the human pancreas. It quickly drops the blood sugar level and
works for a short time. If a rapid-acting insulin is used instead
of a short-acting insulin at the start of dinner, it may prevent severe drops in blood sugar level
in the middle of the night.
Short-acting insulins take effect and wear off more quickly than
long-acting insulins. A short-acting insulin is often used 30 minutes before a meal so that it has time to work. These liquid insulins are clear and do not settle out when
the bottle (vial) sits for a while.
Intermediate- and long-acting insulins contain added substances (buffers) that
make them work over a long time and that may make them look cloudy. When these types of
insulin sit for even a few minutes, the buffered insulin settles to the bottom
of the vial. But insulin glargine (Lantus) and insulin detemir (Levemir) are
clear liquids (not cloudy).
Mixtures of insulin can sometimes be combined in the same syringe, for example, intermediate-acting and rapid- or short-acting insulin. Not all insulins can be mixed together.
For convenience, there are premixed rapid- and intermediate-acting insulin. The insulin will start to work as quickly as the fastest-acting insulin in the combination. It will peak when each type of insulin typically peaks, and it will last as long as the longest-acting insulin. Examples include:
July 11, 2013
E. Gregory Thompson, MD - Internal Medicine & David C.W. Lau, MD, PhD, FRCPC - Endocrinology
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