Insulin Sliding Scale

What Is It?

The insulin sliding scale (also called "reactive" or "corrective" insulin) is a protocol where subcutaneous rapid- or short-acting insulin is administered based solely on the current blood glucose (BG) reading, without accounting for what the patient is eating or any scheduled background insulin. The dose "slides" upward as the BG rises.

Typical example of a low-intensity sliding scale (regular or rapid-acting insulin):

Blood Glucose (mg/dL)	Insulin Dose
< 140	No insulin
141 - 180	2 units
181 - 220	4 units
221 - 260	6 units
261 - 300	8 units
> 300	10 units + notify MD

Scales can be low, moderate, or high intensity depending on insulin sensitivity (e.g., patients on steroids or with obesity may need a more aggressive scale).

How It Is Used

Given with meals (before or immediately after) in non-critically ill inpatients.
When used correctly as a correction factor (also called SSI or RISS - Regular Insulin Sliding Scale), it is added on top of scheduled basal and nutritional (bolus) insulin -- not used alone.
Administered SC; IV insulin infusion is used separately for critical illness or perioperative management.

Corrective/Sliding Scale as Part of Basal-Bolus Regimen

According to The Washington Manual of Medical Therapeutics:

"Scheduled insulin with basal, nutritional, and correction components provides superior glycemic control compared to correction or 'sliding scale' insulin alone."
Meal-time insulin doses should be given shortly before or immediately after meals, and the correction (sliding scale) dose is added to the premeal dose -- not given in isolation.
The glucose threshold for sliding scale correction should be higher at bedtime, or correction insulin should not be given at bedtime at all.
If correction doses are frequently required, adjust the next day's basal or premeal doses.

Why Sliding Scale Alone Is Discouraged

Sliding scale monotherapy (SSI alone, without basal/bolus insulin) has significant drawbacks:

Purely reactive - it treats high glucose after the fact rather than preventing it.
No basal coverage - the patient may be persistently hyperglycemic between doses.
"Chasing" the glucose - doses may cause hypoglycemia followed by rebound hyperglycemia.
No meal adjustment - doesn't account for carbohydrate intake or NPO status.

Tintinalli's Emergency Medicine notes: "Writing orders for sliding scale insulin for admitted patients can lead to undesirable levels of hypoglycemia and hyperglycemia. Sliding scale insulin should not be used for more than 12 hours" for boarding patients.

What Current Guidelines Recommend Instead

A 2025 systematic review in Diabetes Care (Wilson et al., PMID 40117466) analyzing 10 major clinical practice guidelines found:

5 out of 10 guidelines actively advise against sliding scale insulin as monotherapy.
The preferred approach is basal-bolus insulin (long-acting basal + rapid-acting premeal + correction factor).
Target BG: upper limit 180 mg/dL, lower limit 100-140 mg/dL depending on the guideline.

When Sliding Scale Is Still Acceptable

Despite its limitations, SSI still has a role in specific situations:

Setting	Role
Perioperative (minor surgery, diet-controlled T2DM)	Acceptable for short-term glucose correction
TPN/enteral nutrition	Sliding scale to cover hyperglycemia from feeds; total 24-hr SSI dose guides the next-day insulin addition
Very short inpatient stays (<24 hrs)	Low-intensity correction may be sufficient
As an add-on to basal insulin in T1DM (anesthesia)	RISS added on top of basal insulin; titrated to BG measurements

Perioperative Notes

Current Surgical Therapy states: "A basal insulin regimen has been shown to be more effective than a supplemental correctional sliding scale alone" for postoperative patients on the general floor.
Harrison's Principles of Internal Medicine (2025): "Perioperative hyperglycemia should be treated with IV infusion of short-acting insulin or subcutaneous sliding-scale insulin" (with the former preferred for critical/major surgery).
Barash Clinical Anesthesia: In T1DM, a regular insulin sliding scale (RISS) can be added to basal insulin and titrated to BG; alternatively, an insulin infusion of 0.5-1 unit/hour is used.

Key Takeaway

The sliding scale is best used as a correction component added to a basal-bolus regimen, not as a standalone order. Sole reliance on SSI is widely discouraged by current guidelines in favor of scheduled basal-bolus insulin with a correction factor, particularly for non-ICU inpatients.

Sources: The Washington Manual of Medical Therapeutics; Tintinalli's Emergency Medicine; Harrison's Principles of Internal Medicine 22e; Current Surgical Therapy 14e; Barash Clinical Anesthesia 9e; Wilson et al., Diabetes Care 2025 (PMID 40117466)

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