Endocrine & Metabolic/Insulin

Insulins

also: rapid-acting · basal · NovoRapid · Lantus · isophane · insulin

Overview

Replacement therapy — essential in type 1 diabetes and used in type 2. The action-profile (onset/peak/duration) of each type is the high-yield exam content.

Mechanism

Exogenous insulin binds the insulin receptor (tyrosine kinase) → glucose uptake (GLUT4), glycogen/protein/fat synthesis, and inhibition of gluconeogenesis/lipolysis → lowers blood glucose. Also drives K⁺ intracellularly (hence its use in hyperkalaemia).

Indications

Type 1 diabetes (lifelong)
Type 2 diabetes (when oral/injectable therapy insufficient)
DKA / HHS, hyperkalaemia (with glucose), gestational diabetes

The agents

Rapid-acting (lispro/aspart/glulisine)analogue

onset ~15 min, peak 1 h

With meals; also IV in DKA. (NB rapid = 15 min, soluble/short = 30 min.)

Short-acting soluble (Actrapid)human

onset ~30 min

Give 30 min before meals.

Intermediate (isophane/NPH)human

peak 4–12 h

Basal; cloudy.

Long-acting (glargine/detemir/degludec)analogue

flat ~24 h

Basal; once daily; less nocturnal hypo.

Adverse effects

Hypoglycaemiaclassic

The key risk; worse with missed meals, exercise, alcohol; β-blockers mask warning signs.

Weight gaincommon

Lipohypertrophy at injection sitescommon

Rotate sites — lipohypertrophy causes erratic absorption.

Hypokalaemia (drives K⁺ into cells)common

Cautions & contraindications

Hypoglycaemiaall

Never abruptly stop in type 1all

Precipitates DKA.

Interactions

β-blockers mask hypoglycaemia
Steroids/thiazides raise glucose (need more insulin)

Monitoring & kinetics

Capillary/CGM glucose; HbA1c; injection-site rotation,DKA: fixed-rate IV insulin + glucose/K⁺ monitoring

SC (IV for soluble/rapid in DKA). Matching profile to regimen (basal-bolus) is the practical skill.

Source: NICE NG17 — Type 1 diabetes · BNF — Insulins