Insulin is a top cause of prescribing harm. Always write 'units' in full (never 'U' or 'IU'), confirm the concentration (100 units/mL standard), and specify the exact brand and device. Never abbreviate.
Ward principles
- Type 1: never omit basal insulin, even if nil by mouth (use a variable-rate insulin infusion with glucose)
- Prescribe basal plus mealtime rapid-acting analogue for basal-bolus regimens
- Use the dedicated insulin section of the chart
- Check recent capillary glucose and the patient's usual regimen
Hypoglycaemia (glucose below 4)
- Conscious and able to swallow: 15 to 20 g fast-acting carbohydrate (for example glucose tablets or juice)
- Recheck after 15 min and repeat up to 3 times
- Impaired or unsafe swallow: IM glucagon or IV glucose (for example 100 mL of 20%)
- Follow with long-acting carbohydrate and find the cause
Routine
- Prescribe in units, never 'u'
- Right insulin and device
- Do not omit basal in type 1
Caution
- Sick-day rules, renal impairment
- Hypo risk: review the dose
- Align with meals
Hypoglycaemia / DKA
- Under 4: fast-acting carbs or IV glucose
- DKA: fixed-rate insulin, never stop basal
- Senior review
Safe prescribing
1
1. Verify
Patient identity, diabetes type, usual insulin and doses, and allergies.
Patient identity, diabetes type, usual insulin and doses, and allergies.
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2
2. Write clearly
Dose in 'units' written in full, correct device and brand, and the right timing relative to meals.
Dose in 'units' written in full, correct device and brand, and the right timing relative to meals.
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3
3. Pair VRIII with fluid
Prescribe a variable-rate insulin infusion with the correct substrate fluid and glucose monitoring; continue long-acting insulin alongside.
Prescribe a variable-rate insulin infusion with the correct substrate fluid and glucose monitoring; continue long-acting insulin alongside.
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4
4. Educate and hand over
Injection technique, sick-day rules, hypoglycaemia treatment to hand, and clear handover.
Injection technique, sick-day rules, hypoglycaemia treatment to hand, and clear handover.
Common errors to avoid
- 'U' or 'IU' misread as a zero (tenfold overdose)
- Stopping basal insulin in type 1
- VRIII without substrate fluid (hypoglycaemia or ketosis)
- Prescribing mL instead of units
Pitfalls
- Omitting insulin when nil by mouth
- Not rechecking glucose after treating a hypo
- Ambiguous or abbreviated prescriptions
- Ignoring the usual home regimen
MedPrep - www.medprep.uk - Educational revision aid only. Not clinical guidance. Doses are adult examples; check the BNF, current guidelines and local policy, and seek senior advice. Nov 2026