Back

Variable-rate insulin

Ward jobs

VRIII is for patients who can't eat, or whose glucose can't be managed with subcutaneous insulin while unwell. DKA uses a fixed-rate infusion instead.

Continue long-acting (basal) insulin during a VRIII.

Act now

  1. 1

    Prescribe the insulin syringe and a glucose-containing substrate fluid together on the local VRIII chart.

  2. 2

    Choose the starting scale (standard, reduced if insulin-sensitive, increased if insulin-resistant).

Assess

  • Indication: nil by mouth for more than one missed meal, vomiting, or hyperglycaemia not controlled with subcutaneous insulin.
  • Diabetes type, usual regimen, U&E (K⁺), ketones if type 1.

Investigations

  • Capillary glucose hourly; U&E at least daily (watch K⁺ and Na⁺); ketones if type 1 and glucose over 12 mmol/L.

Manage

  • Target glucose 6–10 mmol/L (4–12 acceptable).
  • Don't stop or slow the substrate fluid to treat high glucose — change the insulin rate instead.
  • Glucose under 4 mmol/L: treat the hypo; restart the VRIII within 20 minutes once glucose is over 4, on a lower scale.
  • Glucose above target on two consecutive readings despite a working line: move to the next scale up.
  • Stopping: once eating and drinking, give the usual subcutaneous insulin with a meal and stop the VRIII 30–60 minutes later.

Escalate when

  • Persistently out of range, ketones 3 mmol/L or above (treat as DKA), recurrent hypos, or K⁺ under 3.5: senior and diabetes team.

Doses and prescribing

Soluble insulin (Actrapid or Humulin S)

50 units in 50 mL 0.9% sodium chloride = 1 unit/mL.

Substrate fluid per local VRIII chart — e.g. 0.45% sodium chloride with 5% glucose and 0.15% potassium chloride at a fixed rate based on fluid needs.

Check the BNF and your local formulary before prescribing.

Written to current guidance · sources checked 14 Nov 2026. We watch NICE for updates weekly.

Sources (3)

Reviewed by Aboodee Alhasso, MPharm MRCPharm IP on 14 Nov 2026

For healthcare professionals, as an aid to clinical judgement — not a substitute for it. Follow your local policy and ask a senior when in doubt.