Wellington ICU Drug Manual: Appendices

appendix 11:
Insulin infusion protocol

Wellington ICU Drug Manual - Sliding Scale Insulin logo

Purpose, indications & risks

This protocol standardises the use of insulin infusions in ICU paients. Patients requiring insulin in ICU do not need a previous diagnosis of diabetes. Hyperglycaemia is commonly observed in critically ill patients as part of a stress response or as a side-effect of medication. It is associated with increased morbidity & mortality irrespective of the reason for admission although intensive glucose control (4.5 - 6 mmol/L) may also increase the risk of death.

The default blood glucose level (BGL) target range for patients in Wellington ICU is 6 - 12 mmoL/L

Do not use this pathway in diabetic ketoacidosis (DKA) or hyperglycaemic hyperosmolar states (HHS). Such patients are excluded from this protocol.

Patients with type I diabetes always need insulin. Discuss with medical staff before ceasing insulin for > 1 hour.

Always check blood ketones on admission for all patients with T1DM or T2DM on empagliflozin

This protocol is available as a PDF to print for use at the bedside.

Insulin infusions increase the risk of hypoglycaemia. This risk is higher in unconscious or sedated patients who cannot report symptoms. Infusions may also cause hypokalaemia as insulin promotes cellular uptake of potassium. Monitoring of serum potassium via venous or arterial blood gas is sufficent and may require supplementation.

When to use

  • Measure BGL by finger prick or arterial/venous blood gas sampling
  • If BGL is 4 -12 mmol/L, no action is required. Repeat the BGL 4 hourly
  • If BGL < 4 mmol/L, inform a doctor immediately
  • If BGL > 12 mmol/L, the ICU Insulin Sliding Scale protocol should be commenced
  • Draw up 60 IU Novorapid in 60 mL of 0.9% Saline in a 60 mL syringe
  • Determine the starting scale (either A or B) using the following criteria:
Wellington ICU Drug Manual - Insulin Scale Determination

Monitoring & adjusting

  • Commence the insulin infusion at the rate shown in mLs/hr in the table below for Scale A or Scale B
  • Do not commence on any other scale - these are for later adjustment
  • Check BGL hourly for 4 hrs until within range 6-12 mmol/L
  • If remains in range, decrease frequency of testing to every 2 hrs for next 12 hrs
  • If remains in range for ≥ 12 hrs, decrease frequency of testing to every 4 hrs
  • If BGL > 12 mmol/L, increase infusion/scale (see below). Measure BGL hourly
Wellington ICU Drug Manual - Insulin Rate table

Changing scales

Move UP a scale (from A to B, B to C, C to D etc.) or DOWN a scale (from D to C, C to B, B to A etc.) if the following criteria are met:

Wellington ICU Drug Manual - Scale change

Inform medical staff if any patient requires ≥ 8 mLs/hr (8 IU/hr)

Higher hourly infusion rates can be prescribed in blank Scale E if Scale D is insufficient to achieve blood glucose target range.


  • if BGL < 6 mmol/L and not diabetic, stop the infusion; inform doctor immediately if BGL < 4
  • Recheck BGL every 15 mins until ≥ 6 then restart infusion
  • If BGL < 6 mmol/L in a patient with Type 1 or Type 2 diabetes, move DOWN a scale and start 10% dextrose IV at 40 mL/hr.

Type 1 diabetics require insulin all the time. They are at risk of ketosis if insulin is stopped for > 1 hr. They should almost always have long-acting subcutaneous insulin commenced before discharge.

When to stop intravenous insulin

  • If patient is not diabetic & has required <24 IU insulin in last 24 hours
  • If patient is not diabetic and nasogastric feed or TPN has been stopped
  • After transition to subcut long-acting insulin (see second page of PDF below).
    Do not stop intravenous insulin until subcut long-acting insulin has been given.

When to refer to the in-patient diabetes service
Refer the following patients prior to ICU discharge:

  • All patients with type 1 diabetes, irrespective of reason for ICU admission
  • All patients with severe pancreatitis or after major pancreatic surgery who require insulin
  • Patients with DKA or HHS
  • Patients new to insulin who required ≥ 24 IU intravenously in previous 24 hours

Referrals are electronic through MAP:
Select Patient ⇒ Add New Document ⇒ Diabetes Inpatient Referral