Is it safe to increase NPH insulin dose to omit mealtime insulin in a patient with blood glucose levels of 205 mg/dL at lunch and 172 mg/dL at dinner, on Prednisone and an NPH dose of 22 units with a 1:8 carb ratio?

Increasing NPH to Eliminate Mealtime Insulin is Not Recommended

You should not increase your NPH dose to eliminate mealtime insulin—this strategy will likely worsen your glycemic control and increase hypoglycemia risk. Your current blood glucose readings (205 mg/dL at lunch, 172 mg/dL at dinner) indicate inadequate prandial coverage that requires mealtime insulin, not just more basal insulin. 1, 2

Why This Approach is Problematic

The Steroid-Insulin Mismatch Problem

• Prednisone 15 mg causes peak hyperglycemia between midday and midnight, which is why your lunch (205 mg/dL) and dinner (172 mg/dL) readings are elevated 1, 2
• NPH insulin peaks at 4-6 hours after administration, so increasing the morning dose would create maximum insulin effect in the afternoon when you're already experiencing hyperglycemia 1
• Simply adding more NPH creates a dangerous mismatch: you'll have excessive insulin overnight (causing hypoglycemia) while still having inadequate coverage at meals 2, 3

The Overbasalization Trap

• Your situation demonstrates classic "overbasalization"—attempting to use basal insulin to cover postprandial hyperglycemia 4
• The American Diabetes Association specifically warns against this: if you have a bedtime-to-morning glucose differential ≥50 mg/dL or significant postprandial hyperglycemia, increasing basal insulin is inappropriate 4
• Overbasalization leads to hypoglycemia between meals while failing to control post-meal glucose spikes 4

What You Should Do Instead

Optimize Your Current NPH Dose

• Your NPH dose of 22 units may already be appropriate or even excessive given steroid-induced patterns 1, 2
• First, verify your fasting blood glucose is in target range (100-130 mg/dL)—if it's already controlled, your basal insulin is adequate 2
• If fasting glucose is elevated, increase NPH by only 2 units every 3 days until fasting targets are achieved 1, 2

Address the Real Problem: Prandial Coverage

• Your elevated lunch and dinner readings require mealtime insulin—this cannot be adequately addressed with NPH alone 4, 1
• Continue using your 1:8 carb ratio for mealtime insulin coverage 4
• The American Diabetes Association recommends maintaining prandial insulin when postprandial hyperglycemia persists despite adequate basal insulin 4

Consider Splitting Your NPH Dose

• If midday-to-evening hyperglycemia persists despite adequate mealtime insulin, split your NPH: give 2/3 in the morning and 1/3 before dinner 1, 2
• This provides better coverage for the steroid's hyperglycemic effect throughout the day 1

Critical Monitoring Parameters

What to Watch For

• Check blood glucose fasting, before each meal, and at bedtime while making any adjustments 2
• Target fasting glucose: 100-130 mg/dL 2
• Target pre-meal glucose: 100-140 mg/dL 2
• If you experience any hypoglycemia (glucose <70 mg/dL), immediately reduce the corresponding insulin dose by 10-20% 1, 2

When Prednisone is Tapered

• Reduce your NPH dose by 10-20% for each significant prednisone reduction to prevent hypoglycemia 1, 2
• Your mealtime insulin requirements will also decrease—adjust your carb ratio accordingly 1

Common Pitfalls to Avoid

• Never attempt to cover meal-related hyperglycemia by simply increasing basal insulin—this is the most common error in steroid-induced diabetes management 4, 1
• Don't administer NPH at bedtime for steroid-induced hyperglycemia—the peak action causes nocturnal hypoglycemia while missing the steroid's daytime effect 3
• Avoid making large insulin dose changes (>2-4 units at a time) as this increases hypoglycemia risk 1, 2
• Don't skip blood glucose monitoring—you need data to guide safe adjustments 2

The Bottom Line

Your elevated lunch and dinner readings indicate you need better prandial insulin coverage, not more basal insulin. Increasing NPH to eliminate mealtime insulin would be moving in the wrong direction—you'd likely end up with worse overall control, more hypoglycemia, and greater glucose variability. 4, 1, 2