How to adjust the insulin regimen for a patient on Humulin R (Regular insulin) 20 units TID with a sliding scale and Humulin N (NPH insulin) 25 units BID, who is experiencing morning hypoglycemia and lunchtime hyperglycemia?

Insulin Regimen Adjustment for Morning Hypoglycemia and Lunchtime Hyperglycemia

Immediate Adjustments Required

Reduce the evening Humulin N dose from 25 units to 20 units (20% reduction) and increase the morning Humulin N dose from 25 units to 28-30 units. This addresses the morning hypoglycemia caused by excessive overnight basal insulin while providing better daytime coverage for the elevated lunch glucose 1, 2, 3.

Understanding the Problem

Your current regimen has a critical mismatch:

• Morning hypoglycemia indicates the evening NPH dose (given at dinner or bedtime) is too high, causing excessive insulin action overnight 1, 3, 4
• High lunch glucose suggests inadequate basal insulin coverage during the late morning hours, when the morning NPH dose should be peaking 2, 3, 4

The evening NPH is "overshooting" overnight, while the morning NPH is insufficient to control glucose through to lunch 5, 4.

Step-by-Step Adjustment Protocol

Step 1: Reduce Evening NPH Immediately

• Decrease evening Humulin N from 25 units to 20 units (20% reduction) 1, 2
• This 20% reduction is the standard approach when hypoglycemia occurs without clear cause 1, 2
• Continue monitoring fasting glucose for 3 days before further adjustments 1, 2

Step 2: Increase Morning NPH

• Increase morning Humulin N from 25 units to 28-30 units (approximately 10-20% increase) 1, 2
• The morning NPH dose controls pre-lunch and afternoon glucose levels 2, 3, 4
• Titrate by 2-4 units every 3 days based on pre-lunch glucose readings until lunch glucose reaches 80-130 mg/dL 1, 2

Step 3: Optimize the NPH Split Ratio

• The standard NPH split is 2/3 of total dose in the morning, 1/3 in the evening 2, 3, 6
• Your current 25/25 split (50/50) does not follow this principle 2, 3, 6
• Target split: approximately 30-33 units morning / 15-17 units evening once total dose is optimized 2, 3, 6

Monitoring Requirements

• Check fasting glucose daily to assess evening NPH adequacy 1, 2
• Check pre-lunch glucose daily to assess morning NPH adequacy 1, 2
• Adjust doses every 3 days based on glucose patterns, not single readings 1, 2
• If fasting glucose remains <80 mg/dL, reduce evening NPH by an additional 2 units 1, 2
• If pre-lunch glucose remains >180 mg/dL, increase morning NPH by 2-4 units 1, 2

Critical Considerations for NPH Insulin

Timing of NPH Administration

• Morning NPH should be given before breakfast to provide peak action during late morning/early afternoon 2, 3, 6
• Evening NPH can be given before dinner OR at bedtime, but bedtime administration may provide better overnight coverage with less nocturnal hypoglycemia 5, 4, 7
• Consider moving evening NPH to bedtime (rather than dinner) if morning hypoglycemia persists despite dose reduction 5, 4

NPH Pharmacokinetics

• NPH has a peak action at 4-12 hours and duration of 12-18 hours 8, 5
• This explains why evening NPH peaks overnight (causing morning lows) and morning NPH peaks around lunch 5, 4
• Unlike long-acting analogs (glargine), NPH has a pronounced peak that must be matched to meal timing 5, 4

Managing the Regular Insulin Component

Your Humulin R 20 units TID with sliding scale should continue, but:

• Regular insulin given 30-45 minutes before meals provides optimal postprandial coverage 8
• The sliding scale (3 units per 50 mg/dL over 150) serves as correction insulin only 1, 2
• Do not adjust Regular insulin doses to compensate for NPH timing issues—these are separate components 1, 2

Common Pitfalls to Avoid

• Never give equal morning and evening NPH doses—the 2/3:1/3 ratio accounts for greater insulin sensitivity overnight and reduces nocturnal hypoglycemia risk 2, 3, 6
• Do not increase evening NPH to fix lunch hyperglycemia—this will worsen morning hypoglycemia 1, 2, 5
• Do not decrease morning NPH to prevent morning lows—the evening dose is the culprit 1, 2, 5
• Avoid making adjustments more frequently than every 3 days unless severe hypoglycemia occurs 1, 2

Hypoglycemia Management

• Treat any glucose <70 mg/dL immediately with 15 grams of fast-acting carbohydrate 1, 9
• Recheck glucose in 15 minutes and repeat treatment if needed 1, 9
• If morning hypoglycemia occurs more than twice weekly, reduce evening NPH by an additional 10-20% 1, 2
• Always carry a source of fast-acting carbohydrate and wear diabetic identification 8, 9

When to Consider Regimen Change

If adjustments to the NPH split do not resolve the pattern after 2-3 weeks:

• Consider switching from NPH to a long-acting analog (insulin glargine or detemir) for more predictable basal coverage with less hypoglycemia risk 1, 5, 7
• Long-acting analogs have less pronounced peaks and provide more stable 24-hour coverage 5, 7
• This may be particularly beneficial if nocturnal hypoglycemia persists despite NPH dose reduction 5, 4, 7