GGC Medicines

Adult Therapeutics Handbook

Insulin Sliding Scale
If your clinical area is ready to switch to the new Variable Rate Intravenous Insulin Infusion (VRIII) guideline (see memo for switching criteria) then see guideline on NHSGGC StaffNet / Clinical Info / Clinical Guidelines Directory and search in 'Endocrine' section.


The VRIII guideline is being rolled out across GGC in March 2019 and will replace the Insulin Sliding Scale guideline in the Therapeutics Handbook. If your clinical area is not ready to switch then see Insulin Sliding Scale guideline below.


Insulin Sliding Scale

This sliding scale should NOT to be used to treat people with:

  • Diabetic Ketoacidosis (DKA)
  • Hyperglycaemic Hyperosmolar State (HHS) / Hyperosmolar Non-Ketotic Coma (HONC)

See individual guidelines for the management of these conditions.

This sliding scale can be used to manage glucose levels in people with diabetes mellitus. It can be used in surgical patients with diabetes mellitus undergoing operations however local anaesthetic departments may have their own scales. Prior to using the scale below, discuss with local anaesthetists that they are happy for it to be used. This scale can also be used in medical patients with diabetes mellitus in whom regulation of glucose is deemed important. The principles of the sliding scale are:

  • Desired glucose control is achieved and maintained
  • Avoidance of hypoglycaemia
  • Avoidance of ketosis by providing adequate carbohydrate and insulin
  • Maintenance of fluid and electrolyte balance.

Before starting on the sliding scale it is important to specify the target glucose level and whether intravenous fluids are to be given with insulin. Urea and electrolytes should be checked before starting the sliding scale to guide potassium administration. If patient is already on a background insulin (eg Insulatard®, Lantus® or Levemir®), administer at the usual time whilst using sliding scale, unless advised not to by Diabetes team or anaesthetist.


Preparation: Add 50units of soluble insulin (Actrapid® or Humulin S®), drawn up using an insulin syringe, to 50ml of 0.9% sodium chloride in a 50ml syringe. Infuse IV using a syringe pump and adjust according to sliding scale below, which is an initial guide. Please review insulin rate and blood glucose response on a regular basis (see supplementary notes below) and amend if need be to achieve target blood glucose.

Table 1 – Insulin sliding scale (initial guide)

#See supplementary notes below

Blood glucose (mmol/L) Insulin Infusion Rate (units/hour)
<5 0
5.1–10 1
10.1–15 2
15.1–20 3
>20.1 #4 and call a doctor

Intravenous Fluids (if being given)

The fluid regimen used with this sliding scale is NOT appropriate for fluid resuscitation. If intravenous fluids are to be given, consider using the following regimen (see notes below regarding potassium supplementation).

  1. 500ml bag of 5% glucose containing 20mmol KCI (potassium chloride) over 5 hours THEN
  2. 500ml bag of 5% glucose containing 20mmol KCI over 5 hours THEN
  3. 500ml bag of 5% glucose containing 20mmol KCI over 5 hours THEN
  4. 500ml bag of 5% glucose / 0.9% sodium chloride over 5 hours THEN repeat the process, beginning at number 1.

Potassium Supplementation

Aim for a serum potassium of 4–5mmol/L. Be guided on potassium replacement by U&Es:

  • If baseline potassium is >5mmol/L omit potassium replacement but continue to monitor potassium and re-check U&Es in 4 hours.
  • Be prepared to vary the potassium chloride content of the IV fluids according to plasma potassium levels.
  • In patients with renal failure, chronic kidney disease or oliguria seek advice from a member of the Renal or Diabetes Team or senior medical staff on potassium replacement.

Supplementary Notes

  • Check capillary blood glucose hourly except when it is <5mmol/L and the sliding scale is stopped. In this instance check the capillary blood glucose every 30 minutes. When blood glucose levels are stable capillary blood glucose levels can be checked every two hours.
  • When blood glucose levels are >20.1mmol/L it is important to assess the following:
    • Check pump devices, IV lines and IV cannulae to ensure patients are getting the prescribed insulin dose
    • Consider other causes that could be contributing: sepsis, steroid therapy, obesity.

Review the following at least twice daily (may need to be more frequent depending on the clinical scenario):

  • Sliding scale and blood glucose response
  • Rate of infusion and type of fluid used
  • Potassium level and potassium supplementation.

If you are unsure of how to review or how to adjust any of these parameters please contact a member of your local Diabetes Team. In patients with type 1 diabetes the sliding scale should only be discontinued once SC insulin (containing a long-acting insulin, such as a premixed or background insulin) has been restarted.


Last updated February 2019