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Insulin infusion and glucose control in the ICU, including DKA and HHS: checks, potassium and hypoglycaemia

  • Safe practice

An insulin infusion follows a written protocol: frequent glucose checks, potassium before and during, and a fast response to any low glucose.

Updated

What it is

Intravenous insulin is the usual way to control high glucose in critically ill adults, and the treatment of diabetic ketoacidosis (DKA) and the hyperosmolar hyperglycaemic state (HHS). Insulin is a high-alert medicine, so the infusion follows a nurse-driven or computerised protocol, on a smart pump, with an independent double check where the institution requires it. The nurse checks glucose often, makes sure potassium is known before insulin starts and rechecks it, adds glucose to the fluids when the protocol says, adjusts the rate whenever feeding stops, treats hypoglycaemia at once, and overlaps subcutaneous insulin before the infusion stops. This page gives no doses. Ward-level care of DKA and HHS is on its own page.

What it requires

  • A written insulin infusion protocol with targets, adjustment rules and a hypoglycaemia section.
  • A standard insulin concentration, a smart pump and an independent double check where required.
  • A reliable sample: arterial blood when an arterial line is in place; fingertip samples can read falsely high in shock, on vasopressors, with cold or severe oedema.
  • Potassium, and in DKA the ketones and venous pH, checked on the schedule the protocol sets.

How it is applied (and why)

  1. Check the order, the protocol and the concentration, and do the double check — insulin errors cause severe harm.
  2. Program a smart pump and identify the line as the institutional protocol says — precise rates need a pump with a drug library.
  3. Before starting in DKA or HHS, make sure the potassium result is known — potassium falls once insulin starts.
  4. Check glucose as the protocol says, from the most reliable sample — capillary readings can be wrong in shock.
  5. Adjust the rate using the current value and its trend — protocols that use the trend work better than the last value alone.
  6. When glucose falls to the protocol's level in DKA, add glucose to the fluids as ordered — ketoacidosis still needs insulin.
  7. Recheck potassium about 2 hours after starting and then about every 4 hours in DKA, as ordered — low potassium is common and dangerous.
  8. If feeds stop or are paused, review the insulin rate with the protocol at once — insulin without nutrition causes hypoglycaemia.
  9. For low glucose, stop the infusion, treat as the protocol says, recheck and report — sedated patients may show no symptoms.
  10. Give the subcutaneous insulin before stopping the infusion, as ordered — the overlap prevents rebound hyperglycaemia or a DKA relapse.

In nursing practice

  • Hypoglycaemia is below 3.9 mmol/L, and below 3.0 mmol/L is clinically significant; both are reported.
  • Large swings in glucose are linked with worse outcomes: aim for a steady value within the target range.
  • In HHS glucose and sodium must not fall too fast; the team sets the limits and the nurse reports a fast fall.
  • Report new drowsiness or confusion during DKA treatment: cerebral oedema is rare but serious.
  • Older adults and people with heart or kidney failure are at higher risk of fluid overload during treatment: check lungs, breathing and balance.

Common mistakes

  • Starting insulin in DKA before the potassium is known.
  • Leaving the infusion unchanged when the feed is stopped for a procedure.
  • Trusting a fingertip glucose in a patient in shock.
  • Stopping the infusion before the subcutaneous insulin has been given.
  • Restarting at the old rate after hypoglycaemia instead of the rate the protocol sets.

Test yourself

Think of the answer, then tap the question to see it.

Why must potassium be known before insulin is started in DKA?

Potassium falls once insulin starts; if it is below 3.5 mmol/L, insulin is delayed while potassium is replaced.

Why can a fingertip glucose be misleading in a patient in shock?

Poor skin perfusion, vasopressors, cold and oedema can make it read falsely high; an arterial sample is preferred when available.

What should the nurse do when the feed stops in a patient on an insulin infusion?

Review the insulin rate with the protocol at once, because insulin without nutrition is a common cause of hypoglycaemia.

Why is subcutaneous insulin given before the infusion is stopped?

The overlap prevents rebound hyperglycaemia or a relapse of ketoacidosis when the infusion stops.

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Educational content for students; it does not replace your institution's protocols, supervised clinical training or a prescriber's order. Dose-calculation examples use made-up numbers: they are educational, not a clinical order.

Sources: Hyperglycaemic crises in adults with diabetes: a consensus report (Umpierrez GE et al., Diabetologia 2024;67:1455-1479) (American Diabetes Association, EASD, JBDS, AACE and DTS; Diabetologia, open access in PubMed Central, 2024); Management of dysglycemia in critically ill adults: current evidence, clinical practice and future directions (Idrees T et al., BMJ Open Diabetes Res Care 2026;14(5):e006533) (BMJ Open Diabetes Research & Care, open access in PubMed Central, 2026); Surviving Sepsis Campaign: international guidelines for management of sepsis and septic shock 2021 (Evans L et al., Intensive Care Med 2021;47:1181-1247) (Society of Critical Care Medicine and European Society of Intensive Care Medicine, open access in PubMed Central, 2021).

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