What should the Lantus dose, carbohydrate ratio, and correction scale be for a 76-year-old patient with type 2 diabetes mellitus on Lantus, Amaryl, Jardiance, and metformin, with impaired renal function, who received dexamethasone and is at risk for ileus?

Insulin Management for Hospitalized Type 2 Diabetes Patient on Dexamethasone

Immediate Medication Adjustments Required

Stop Amaryl (glimepiride) immediately and hold Jardiance until the patient is eating regularly. Sulfonylureas are explicitly not recommended during glucocorticoid therapy and carry unacceptable hypoglycemia risk in NPO/poor oral intake patients 1. SGLT2 inhibitors should be held 3-4 days before surgery and in patients at risk for ileus due to euglycemic DKA risk 1.

Continue metformin 500 mg BID unless contraindicated (eGFR >60 mL/min/1.73 m² with Cr 0.94 supports continuation) 1.

Dexamethasone-Induced Hyperglycemia Management

Basal Insulin Dosing

Increase Lantus to address dexamethasone-related hyperglycemia using the following algorithm:

• Add 0.1-0.3 units/kg/day of NPH insulin twice daily (give 2/3 of total dose in morning, 1/3 in early evening) to the existing Lantus regimen 1
• For this 108 kg patient: Add NPH 22 units AM and 11 units early evening (using 0.3 units/kg/day = 32.4 units total, split 2/3:1/3)
• Alternatively, increase total basal insulin by 40-60% to account for steroid-induced insulin resistance 1
• Current Lantus total = 85 units/day; increase to approximately 120-135 units/day, maintaining AM/PM split

Critical timing consideration: Dexamethasone causes predominantly afternoon and evening hyperglycemia 1. The PM Lantus dose (currently 45 units) should be increased more aggressively than the AM dose.

Prandial/Correction Insulin Protocol

For NPO or minimal intake status:

• Basal insulin: 0.1-0.25 units/kg/day given high-risk features (age 76, potential ileus) 2
• For 108 kg patient: 11-27 units/day total basal insulin
• However, given dexamethasone use, maintain higher basal dosing at 0.3 units/kg/day = 32 units/day minimum 1
• Correction scale only: Use simplified sliding scale with rapid-acting insulin:
  • Glucose >250 mg/dL: 2 units rapid-acting insulin
  • Glucose >350 mg/dL: 4 units rapid-acting insulin 2

When advancing to clear liquids/regular diet:

• Total daily dose: 0.3-0.5 units/kg/day (32-54 units/day for 108 kg patient) 2
• Split 50% basal, 50% prandial 1, 2
• Example: 40 units total = 20 units basal (10 units AM + 10 units PM Lantus) + 20 units prandial (7-7-6 units with meals)
• Add dexamethasone adjustment: Increase prandial/correction insulin by additional 40-60% 2

Carbohydrate Ratio (When Eating)

Initial carbohydrate-to-insulin ratio calculation:

• Formula: 450 ÷ Total Daily Dose (TDD) 2
• Using estimated TDD of 40 units: 450 ÷ 40 = 1:11 ratio (1 unit per 11 grams carbohydrate)
• With dexamethasone, use more aggressive ratio of 1:7-8 to account for 40-60% increased insulin needs 1, 2

Correction Scale (Insulin Sensitivity Factor)

Correction factor calculation:

• Formula: 1500 ÷ TDD 2
• Using TDD of 40 units: 1500 ÷ 40 = 1:38 (1 unit lowers glucose by 38 mg/dL)
• With dexamethasone, use more potent correction factor of 1:25-30 to account for increased insulin resistance 1

Target glucose: 140-180 mg/dL for non-critically ill hospitalized patients 2

Specific Dosing Recommendation for This Patient

Current Status (NPO/At Risk for Ileus):

1. Lantus: 15 units AM, 20 units PM (total 35 units/day = 0.32 units/kg/day)
2. Correction insulin only: Aspart/lispro using simplified scale above
3. Hold Amaryl and Jardiance
4. Continue metformin 500 mg BID

When Advancing to Clear Liquids/Diet:

1. Lantus: 20 units AM, 25 units PM (total 45 units basal)
2. Prandial insulin: 8 units before each meal (total 24 units prandial)
3. Carb ratio: 1:8 (1 unit per 8 grams carbohydrate)
4. Correction factor: 1:25 (1 unit lowers glucose by 25 mg/dL)
5. Target glucose: 140-180 mg/dL

Critical Monitoring and Adjustment

Check point-of-care glucose:

• Every 4-6 hours if NPO 2
• Before each meal and bedtime when eating 2

Titrate basal insulin by 4 units every 3 days if fasting glucose ≥180 mg/dL 2

Reduce insulin by 10-20% immediately if hypoglycemia occurs 2

When dexamethasone is stopped, reduce total insulin doses by 40-60% immediately to prevent severe hypoglycemia 1

Common Pitfalls to Avoid

• Never use sliding scale insulin as monotherapy—this approach is explicitly condemned and leads to dangerous glucose fluctuations 1, 2
• Never give rapid-acting insulin at bedtime due to nocturnal hypoglycemia risk 2
• Do not continue sulfonylureas during steroid therapy—unacceptably high hypoglycemia rates 1
• Recognize that insulin requirements will drop precipitously when dexamethasone is discontinued 1