Topic Overview

Insulin is used to treat people with 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 is made by different companies. Make sure you use the same type of insulin consistently.

Types of insulin

Type	Examples	Appearance	When it starts to work (onset)	The time of greatest effect (peak)	How long it lasts (duration)
Rapid-acting
	Apidra (insulin glulisine)	Clear	5–15 minutes	30–60 minutes	3–5 hours
	Humalog (insulin lispro)	Clear	5–15 minutes	30–90 minutes	3–5 hours
	NovoRapid (insulin aspart)	Clear	5–15 minutes	40–50 minutes	3–5 hours
Short-acting
	Humulin-R (insulin regular)	Clear	30 minutes	1½–2 hours	6–8 hours
Intermediate-acting
	Humulin-N (insulin NPH)	Cloudy	1–4 hours	4–12 hours	14–24 hours
Long-acting
	Lantus (insulin glargine)	Clear	1–2 hours	Minimal peak	Up to 24 hours
	Levemir (insulin detemir)	Clear	2 hours	Minimal peak	Up to 24 hours

Rapid-acting insulins work over a narrow, more predictable range of time. The insulin Humalog is a quick-acting insulin with a short length (duration) of action. NovoRapid is now approved for use in insulin pumps.

Rapid- and short-acting types of insulin take effect and wear off more quickly than long-acting insulins. The liquid insulins are clear and do not settle out when the bottle (vial) sits for a while. Rapid-acting insulin acts most like insulin 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 before dinner instead of a short-acting insulin, it may prevent severe drops in the blood sugar level in the middle of the night.

Intermediate- and long-acting types of insulin contain added substances (buffers) that make them work over a long time and may appear 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.