Insulin saves lives, but it’s also one of the medicines most often involved in serious harm in hospitals. Patient safety organisations worldwide list it as a “high-alert medication”: errors such as the wrong dose, wrong insulin, wrong time or omitted doses can cause severe hypoglycaemia or diabetic ketoacidosis. With diabetes rising globally, every nurse needs to handle insulin confidently and safely.
Types of insulin
| Type | Examples | Onset (approx.) | Typical use |
|---|---|---|---|
| Rapid-acting analogue | Lispro, aspart, glulisine | 10–15 minutes | With meals; correction doses |
| Short-acting (soluble/regular) | Human soluble insulin | About 30 minutes | Before meals; IV insulin infusions |
| Intermediate-acting | Isophane (NPH) | 1–2 hours | Once or twice daily background |
| Long-acting analogue | Glargine, detemir, degludec | 1–2 hours, lasts ~24 hours or longer | Once (sometimes twice) daily background |
| Pre-mixed | e.g. 30/70 mixtures | Varies | Twice daily with meals |
Check the product information for the specific brand. Many insulins have similar-sounding names (for example, Humalog and Humalog Mix, Novorapid and Novomix): read the full name and strength every time.
The golden safety rules
- Never abbreviate “units” as “U” or “IU”. “10U” can be misread as 100. Write “units” in full.
- Always use an insulin syringe or pen. Never draw insulin from a pen cartridge or vial into a standard syringe, which has caused fatal overdoses.
- Check the strength: most insulin is 100 units/ml (U100), but higher-strength products (U200, U300, U500) exist. Never transfer these into syringes.
- Two-person check where policy requires, especially for IV insulin.
- Check blood glucose before giving, and consider the patient’s food intake.
- Never omit background (basal) insulin in type 1 diabetes, even if the patient is nil by mouth. Omission can lead to DKA within hours. Escalate for advice instead.
- Patient pens are for one patient only; never share pens, even if the needle is changed.
Timing with meals
One of the commonest hospital problems is mealtime insulin given when food is delayed, or food arriving long after insulin. Coordinate with catering and the patient. Rapid-acting insulin is usually given immediately before (or sometimes just after) eating; soluble insulin about 30 minutes before.
Injection technique
- Use the shortest suitable needle (4 mm pen needles are suitable for most adults) at 90°, usually without a skin lift.
- Sites: abdomen, thighs, buttocks, upper arms. Rotate sites to prevent lipohypertrophy (fatty lumps), which causes erratic absorption.
- Check sites for lumps during assessments.
- Prime pens (air shot of 2 units) before each injection.
- Hold the needle in for about 10 seconds after injecting.
- Roll (don’t shake) cloudy insulins to mix.
Storage
- Unopened insulin: refrigerator, 2–8°C. Do not freeze.
- In-use insulin: usually at room temperature (below about 25–30°C, depending on product) for up to about 4 weeks. Label with the opening date.
- In hot climates without reliable refrigeration, clay pot coolers and other cooling methods can help; advise patients accordingly.
Self-management in hospital
Many people with diabetes manage their insulin better than anyone else. Where safe and local policy allows, support self-administration, and listen to patients who say a dose looks wrong.
Recognising and treating hypoglycaemia
Shakiness, sweating, hunger, confusion, behaviour change, drowsiness or seizures. Treat promptly with fast-acting glucose and recheck. See our hypoglycaemia guide.
IV insulin infusions
- Used in DKA, hyperosmolar states, and some peri-operative and critical care situations.
- Use standardised concentrations (commonly 1 unit/ml) and infusion pumps.
- Hourly capillary glucose (or as protocol) and potassium monitoring.
- See our DKA guide.
Related: Capillary blood glucose monitoring · Rights of medication administration · Type 2 diabetes education
Based on ISMP high-alert medication guidance, Joint British Diabetes Societies (JBDS) inpatient guidelines and FIT injection technique recommendations. Educational content: always check product information and local policy.