How to switch from Lantus (insulin glargine) 20 units twice a day to NPH (Neutral Protamine Hagedorn) insulin twice a day?

Switching from Lantus 20 Units Twice Daily to NPH Twice Daily

When converting from Lantus (insulin glargine) 20 units twice daily (total 40 units/day) to NPH twice daily, use 80% of the total Lantus dose as your starting NPH dose, which equals 32 units total NPH per day, split as approximately 21 units before breakfast and 11 units before dinner (2/3 morning, 1/3 evening). 1

Conversion Algorithm

Step 1: Calculate Total NPH Dose

• Current total daily Lantus dose: 40 units (20 units × 2)
• Starting NPH dose: 32 units total (80% of 40 units) 1
• This dose reduction accounts for the different pharmacokinetic profiles and helps prevent hypoglycemia during the transition 1

Step 2: Split the NPH Dose

• Morning dose (before breakfast): 21 units (2/3 of total) 1
• Evening dose (before dinner): 11 units (1/3 of total) 1
• This distribution pattern aligns with typical insulin requirements and NPH's intermediate-acting profile 1

Step 3: Titration Protocol

• Monitor fasting plasma glucose to assess adequacy of the evening NPH dose 1
• Increase dose by 2 units every 3 days if glucose remains above target without hypoglycemia 1
• For hypoglycemia: Determine the cause; if no clear reason exists, lower the corresponding dose by 10-20% 1

Critical Monitoring Parameters

Blood Glucose Targets

• Check fasting glucose to adjust evening NPH dose 1
• Check pre-dinner glucose to adjust morning NPH dose 1
• Monitor for nocturnal hypoglycemia, which is more common with NPH than with Lantus 2, 3

Hypoglycemia Risk

• NPH carries significantly higher risk of hypoglycemia compared to Lantus, particularly nocturnal episodes (26-59% increased risk) 3
• The intermediate-acting profile of NPH creates a pronounced peak at 4-6 hours post-injection, unlike Lantus's flat profile 2, 3
• Patients should be counseled about this increased risk and prescribed glucagon for emergencies 1

Important Clinical Considerations

Why This Conversion May Be Necessary

• Cost considerations: NPH is significantly less expensive than Lantus 1
• The American Diabetes Association guidelines acknowledge NPH as an appropriate basal insulin option when cost is a barrier 1

Common Pitfalls to Avoid

• Do not convert unit-for-unit: Always use the 80% reduction to prevent hypoglycemia during transition 1
• Do not give NPH at bedtime initially: The 2/3 morning, 1/3 evening split is preferred for twice-daily regimens 1
• Do not delay dose adjustments: Reassess every 3 days and titrate based on glucose patterns 1

When to Reconsider This Switch

• If the patient develops recurrent hypoglycemia despite dose adjustments, consider switching back to a basal analog 1
• If the patient frequently forgets evening doses, morning-only long-acting basal insulin would be more appropriate 1
• Patients with hypoglycemia unawareness are poor candidates for NPH due to its peaked action 1, 3

Additional Therapy Considerations

• If the patient is not already on a GLP-1 receptor agonist, consider adding one to reduce insulin requirements and hypoglycemia risk 1
• If prandial coverage is needed, NPH can be mixed with short- or rapid-acting insulin to reduce injection burden 1