Class Explorer · Endocrine

Insulins

Replacement of the hormone itself. The molecule is the same job in every product; what is bought and sold is the time-action profile.

Members

Insulin glargineThe flat background insulin that covers the fasting state.Insulin aspartMealtime insulin that acts fast enough to be taken with the food.

Also in this class: Insulin detemir · Insulin degludec · Insulin lispro · NPH · Regular human insulin. Full pages arrive as the library grows.

Compare the members

Drug	Onset	Peak	Duration
Insulin glargine	1 to 2 h	Essentially flat	~24 h
Insulin aspart	10 to 20 min	1 to 3 h	3 to 5 h

Insulin glargine

Onset: 1 to 2 h
Peak: Essentially flat
Duration: ~24 h

Insulin aspart

Onset: 10 to 20 min
Peak: 1 to 3 h
Duration: 3 to 5 h

Shared across the class

Indications: Type 1 diabetes, always · Type 2 diabetes when other agents are insufficient · Hyperglycemic emergencies
Adverse effects: Hypoglycemia · Weight gain · Lipohypertrophy at unrotated sites
Contraindications: Hypoglycemia at the time of administration
Monitoring: Capillary glucose in a pattern that matches the insulin being titrated · HbA1c · Injection sites · Hypoglycemia frequency, severity and awareness

What makes each agent different

Basal insulin covers the fasting state and is titrated against the morning glucose. Bolus insulin covers the meal and is titrated against what happens after it. Titrating one against the other's number is the commonest insulin error there is.
Analogue basals (glargine, degludec) are flatter than NPH and cause less nocturnal hypoglycemia; NPH has a peak and is cheaper.
Rapid analogues are given with the meal; regular human insulin needs 30 minutes' lead time. Getting that backwards produces a hypoglycemia before the food arrives.

Insulin is never stopped in type 1 diabetes, including when the patient is not eating. Stopping basal insulin during illness is how ketoacidosis is manufactured.

Units are written in full. 'U' misread as a zero is one of the oldest and most lethal prescribing errors on record.

Last reviewed 2026-08-16 · Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed.