For an adult with severe hyperglycemia (blood glucose 281–515 mg/dL) on insulin glargine (Lantus) 10 units and an insulin drip delivering 0.5 units/hour overnight, what insulin‑sensitivity correction factor and carbohydrate‑to‑insulin ratio should be used?

Insulin Regimen Adjustment for Severe Hyperglycemia on Insulin Drip

This patient requires immediate transition to a scheduled basal-bolus insulin regimen with aggressive dose titration, not continuation of sliding-scale correction doses alone.

Immediate Regimen Changes Required

Calculate Total Daily Dose from IV Insulin Requirements

• The patient received 10 units of Lantus plus an additional 0.5 units/hour overnight (12 hours) = 6 units, totaling approximately 16 units over 24 hours as a baseline requirement 1.
• Blood glucose levels of 281–515 mg/dL indicate this dose is grossly inadequate and the patient requires 0.3–0.5 units/kg/day as total daily insulin given the severity of hyperglycemia 1, 2.
• For severe hyperglycemia with glucose >300 mg/dL, start with a total daily dose of 0.4–0.5 units/kg/day, split 50% as basal insulin and 50% as prandial insulin divided among three meals 1, 2.

Basal Insulin (Lantus) Adjustment

• Increase Lantus immediately to 0.2–0.25 units/kg/day (approximately 50% of the calculated total daily dose) 1, 2.
• Titrate basal insulin by 4 units every 3 days if fasting glucose remains ≥180 mg/dL until fasting blood glucose reaches 80–130 mg/dL 1, 2.
• The current 10 units is insufficient; blood glucose in the 200s–500s mg/dL reflects both inadequate basal coverage AND postprandial excursions requiring mealtime insulin 2.

Prandial Insulin Initiation

• Start rapid-acting insulin (lispro, aspart, or glulisine) at 4 units before each of the three largest meals, or use 10% of the current basal dose 1, 2.
• Administer prandial insulin 0–15 minutes before meals for optimal postprandial glucose control 1, 3.
• Titrate prandial insulin by 1–2 units or 10–15% every 3 days based on 2-hour postprandial glucose readings, targeting postprandial glucose <180 mg/dL 1, 2.

Calculating Correction Factor and Carbohydrate Ratio

Insulin Sensitivity Factor (Correction Factor)

• Use the formula ISF = 1500 ÷ Total Daily Dose (TDD) for regular insulin or ISF = 1700 ÷ TDD for rapid-acting analogs 1, 4, 5.
• Once the total daily dose is established (e.g., 40 units/day), the correction factor would be 1500 ÷ 40 = 37.5 mg/dL per unit (meaning 1 unit of insulin lowers blood glucose by approximately 37.5 mg/dL) 1, 4.
• Recalculate the correction factor every few weeks as the total daily dose changes, not daily 1.

Carbohydrate-to-Insulin Ratio

• Use the formula CIR = 450 ÷ TDD for rapid-acting insulin analogs or CIR = 500 ÷ TDD for regular insulin 1, 4, 5.
• For a total daily dose of 40 units, the carbohydrate ratio would be 450 ÷ 40 = 11.25 grams of carbohydrate per 1 unit of insulin 1, 4.
• CIR has diurnal variance: breakfast typically requires more insulin per gram of carbohydrate (use 300 ÷ TDD), while lunch and dinner require less (use 400 ÷ TDD) 6.
• A common starting ratio is 1 unit per 10–15 grams of carbohydrate, adjusted based on postprandial glucose patterns 1.

Critical Pitfall: Sliding-Scale Insulin as Monotherapy

• Sliding-scale insulin as the sole treatment is explicitly condemned by all major diabetes guidelines and should be immediately discontinued 1, 2.
• Only 38% of patients on sliding-scale alone achieve mean glucose <140 mg/dL, versus 68% with scheduled basal-bolus regimens, with no increased hypoglycemia risk when properly implemented 1.
• Correction doses are intended only as supplements to scheduled basal and prandial insulin, never as a replacement 1.
• For correction doses, use 2 units of rapid-acting insulin for pre-meal glucose >250 mg/dL and 4 units for glucose >350 mg/dL, in addition to scheduled doses 1.

Monitoring and Titration Protocol

Daily Monitoring Requirements

• Check fasting blood glucose every morning during the titration phase to guide basal insulin adjustments 1, 2.
• Check pre-meal and 2-hour postprandial glucose to guide prandial insulin adjustments 1, 2.
• For hospitalized patients eating regular meals, check point-of-care glucose before each meal and at bedtime 1.

Hypoglycemia Management

• If hypoglycemia occurs (glucose <70 mg/dL), treat immediately with 15 grams of fast-acting carbohydrate and reduce the implicated insulin dose by 10–20% 1, 2.
• Never administer rapid-acting insulin at bedtime as a sole correction dose, as this markedly raises nocturnal hypoglycemia risk 1, 3.

Foundation Therapy Verification

• Ensure the patient is on metformin (up to 2000–2550 mg daily) unless contraindicated, as this combination provides superior glycemic control with reduced insulin requirements and less weight gain 1, 2.
• Consider discontinuing sulfonylureas when advancing beyond basal-only insulin to prevent hypoglycemia 1.

Expected Outcomes

• With appropriate basal-bolus therapy at weight-based dosing, 68% of patients achieve mean blood glucose <140 mg/dL 1.
• HbA1c reduction of 2–3% is achievable with proper insulin intensification over 3–6 months 1.
• Target glucose range: fasting/pre-meal 80–130 mg/dL and postprandial <180 mg/dL 1, 2.