What should the morning NPH (Neutral Protamine Hagedorn) insulin dose be for a 65-year-old patient with type 1 diabetes, currently taking Lantus (insulin glargine) 8 units daily, hydrocortisone every 8 hours, with impaired renal function (creatinine level 4.61), and a carb ratio of 1:12 with medium correction factor?

Morning NPH Insulin Dosing for Type 1 Diabetes with Steroid-Induced Hyperglycemia and Renal Impairment

Recommended AM NPH Dose

Start with 26-35 units of NPH insulin in the morning, calculated as 0.3-0.4 units/kg (87 kg × 0.3-0.4 = 26-35 units), specifically to counteract the steroid-induced hyperglycemia from hydrocortisone every 8 hours. 1

Rationale for This Dose

• Morning NPH administration is specifically recommended for steroid-induced hyperglycemia to match the pharmacokinetic profile of glucocorticoids, which peak 4-8 hours after administration 1, 2

• The standard starting dose of 0.1-0.2 units/kg (8.7-17.4 units) is insufficient for patients on high-dose glucocorticoids, who require 40-60% more insulin than standard dosing 2

• For high-dose glucocorticoid therapy, initial NPH dosing should be 0.3-0.4 units/kg per day, which for this 87 kg patient equals 26-35 units 1

• The current Lantus dose of 8 units daily should be continued as basal coverage, with the NPH added specifically to address the steroid effect 1

Critical Adjustments for Renal Impairment (Cr 4.61)

• Reduce the calculated dose by 20% due to severe renal impairment (CrCl significantly reduced with Cr 4.61), bringing the starting dose to approximately 21-28 units 3

• Patients with impaired renal function have increased risk of hypoglycemia due to decreased insulin clearance and impaired renal gluconeogenesis 3

• Morning administration is particularly important in renal impairment to allow better monitoring during waking hours and reduce risk of undetected nocturnal hypoglycemia 3

Practical Starting Recommendation

Begin with 24 units of NPH insulin in the morning (mid-range of the adjusted 21-28 unit calculation), administered at the same time as the morning hydrocortisone dose.

Titration Protocol

• Increase by 2 units every 3 days until fasting plasma glucose reaches target (100-180 mg/dL for this post-transplant-like scenario) without hypoglycemia 4, 3

• If hypoglycemia occurs, reduce the dose by 10-20% immediately 4, 1, 2, 3

• Monitor blood glucose every 4-6 hours during initial titration, particularly important given the renal impairment 1, 3

Adjusting the Carbohydrate Ratio

• The current 1:12 carb ratio is too conservative for high-dose steroid therapy

• Change to 1:8-10 carb ratio (more aggressive) to account for steroid-induced insulin resistance 1

• For meals with greatest postprandial excursions, consider 1:6 ratio 1

• As steroids are tapered, the carb ratio should be liberalized back toward 1:10-12 2

Correction Factor Adjustment

• The "medium correction" needs to be more aggressive on steroids

• Use the 1800 rule: 1800 ÷ total daily insulin dose = correction factor 1

• With current total daily dose of approximately 32-40 units (8 units Lantus + 24 units NPH + prandial insulin), correction factor should be approximately 1 unit per 45-56 mg/dL above target 1

• Recommended correction scale for blood glucose >150 mg/dL:

  • 150-200 mg/dL: 2 units 1
  • 201-250 mg/dL: 4 units 1
  • 251-300 mg/dL: 6 units 1
  • 301-350 mg/dL: 8 units 1

  • 350 mg/dL: 10 units and notify provider 1

Critical Considerations for This Complex Patient

Type 1 Diabetes Specifics

• Never discontinue basal insulin (Lantus) even if NPH is added, as this patient has type 1 diabetes and requires continuous basal coverage to prevent diabetic ketoacidosis 4, 1

• The 8 units of Lantus should continue unchanged initially, with NPH added on top specifically for steroid coverage 1

Steroid Tapering Protocol

• As hydrocortisone is reduced, decrease NPH by 10-20% for each significant steroid dose reduction 1, 2

• The Lantus dose should remain stable during steroid taper 1

• Failing to reduce NPH as steroids taper is a common pitfall that leads to severe hypoglycemia 1, 2

Renal Function Monitoring

• Insulin requirements may fluctuate with changes in renal function, requiring more frequent monitoring and dose adjustments 3

• Prescribe glucagon for emergent hypoglycemia, particularly important given the renal impairment 3

• Consider more frequent blood glucose checks (every 4 hours) rather than standard 6-hour intervals 3

Alternative Approach if Glycemic Control Inadequate

• If once-daily morning NPH fails to achieve targets, convert to twice-daily NPH regimen: 2/3 of total dose in morning, 1/3 before dinner 4, 2

• For conversion from once-daily to twice-daily NPH, use 80% of the current total NPH dose split as above 4

• If hypoglycemia becomes problematic despite dose adjustments, consider switching to a long-acting basal analog after steroid discontinuation 4, 3

Common Pitfalls to Avoid

• Failing to match NPH timing with steroid administration leads to inadequate coverage of steroid-induced hyperglycemia 1

• Using bedtime NPH in renal impairment increases risk of undetected nocturnal hypoglycemia 3

• Not reducing insulin doses proportionally during steroid taper results in severe hypoglycemia 1, 2

• Discontinuing basal insulin (Lantus) in type 1 diabetes can precipitate diabetic ketoacidosis 4, 1