What is the appropriate conversion from Novolin N (human NPH insulin) to Lantus (insulin glargine)?

Conversion from Novolin N (NPH) to Lantus (Insulin Glargine)

Direct Conversion Recommendation

When converting from NPH insulin to Lantus, use 80% of the total daily NPH dose if the patient is on twice-daily NPH, or maintain a 1:1 unit-for-unit conversion if switching from once-daily bedtime NPH. 1, 2

Specific Conversion Algorithms

From Twice-Daily NPH to Once-Daily Lantus

• Calculate the total daily NPH dose (morning + evening doses combined) 1
• Administer 80% of this total as a single daily dose of Lantus 1, 2, 3
• Example: If a patient takes NPH 20 units in the morning and 10 units at bedtime (total 30 units), start Lantus at 24 units once daily 1

From Once-Daily Bedtime NPH to Once-Daily Lantus

• Use a 1:1 unit-for-unit conversion when switching from once-daily bedtime NPH to once-daily Lantus 1, 2, 3
• Example: If a patient takes NPH 30 units at bedtime, start Lantus at 30 units once daily 1, 2, 3

Timing and Administration

• Administer Lantus once daily at the same time each day—this can be morning, evening, or bedtime based on patient preference and lifestyle 1, 3, 4
• Unlike NPH, Lantus provides a relatively constant basal level with no pronounced peak, eliminating the need for twice-daily dosing in most patients 4, 5, 6
• The flat 24-hour pharmacokinetic profile of Lantus allows flexible timing without compromising glycemic control 4, 5, 6

Post-Conversion Monitoring and Titration

Immediate Monitoring Requirements

• Increase blood glucose monitoring frequency during the first 2-4 weeks after conversion 1, 3
• Check fasting glucose daily to guide dose adjustments 1, 7
• Monitor for hypoglycemia, particularly nocturnal episodes, which are significantly reduced with Lantus compared to NPH 4, 5, 8

Systematic Titration Protocol

• If fasting glucose is 140-179 mg/dL: increase Lantus by 2 units every 3 days 1, 7
• If fasting glucose is ≥180 mg/dL: increase Lantus by 4 units every 3 days 1, 7
• Target fasting glucose: 80-130 mg/dL 1, 7, 2
• If hypoglycemia occurs (glucose <70 mg/dL): immediately reduce the dose by 10-20% 1, 7, 2

Clinical Advantages of Lantus Over NPH

Reduced Hypoglycemia Risk

• Lantus reduces overall symptomatic hypoglycemia by 11% compared to NPH 5
• Nocturnal hypoglycemia is reduced by 26% with Lantus 5
• Severe hypoglycemia is reduced by 46% and severe nocturnal hypoglycemia by 59% with Lantus 5, 8
• In intensively treated type 1 diabetes, severe hypoglycemic episodes decrease from 1.2 per patient per year with NPH to 0.5 with Lantus 8

Improved Glycemic Control

• Lantus achieves equivalent or superior HbA1c control compared to NPH with less hypoglycemia 4, 5, 9
• Fasting blood glucose levels are significantly lower with Lantus, especially in patients previously on twice-daily NPH 4, 9
• The peakless profile eliminates the pronounced insulin peak of NPH that occurs 4-6 hours post-injection, reducing glucose variability 4, 6

Weight and Dosing Benefits

• Patients switching to Lantus experience no significant weight gain, whereas NPH-treated patients show significant weight increase 8
• Total daily insulin dose often decreases after conversion to Lantus without compromising glycemic control 8, 9

Special Populations and Considerations

Type 1 Diabetes

• In type 1 diabetes, Lantus typically provides approximately one-third of total daily insulin requirements 2
• Must be used with short-acting prandial insulin to cover meals 1, 3, 4
• The remaining two-thirds of insulin needs should be met with rapid-acting insulin before meals 2

Type 2 Diabetes

• For insulin-naïve type 2 diabetes patients, start Lantus at 0.2 units/kg or up to 10 units once daily 1, 3
• When converting from NPH in type 2 diabetes, Lantus provides superior glycemic control compared to once-daily NPH 4, 6
• Continue metformin (unless contraindicated) when adding or converting to Lantus, as this combination reduces total insulin requirements by 20-30% 1, 7

Patients with Renal Impairment

• Start conservatively with 80% of the previous NPH dose due to decreased insulin clearance and increased hypoglycemia risk 2
• Titrate cautiously with more frequent glucose monitoring 2

Elderly Patients (>65 years)

• Begin with 0.1-0.25 units/kg/day to reduce hypoglycemia risk due to increased insulin sensitivity 7
• Use the 80% conversion rule even for once-daily NPH in this population 2

Critical Pitfalls to Avoid

Do Not Mix or Dilute Lantus

• Never mix Lantus with any other insulin or solution—it must be administered separately 1, 3, 6
• The low pH formulation of Lantus (pH 4) causes precipitation when mixed with other insulins 3, 6
• Use a separate syringe that has not been used for other insulin products 6

Avoid Intravenous or Pump Administration

• Do not administer Lantus intravenously or via an insulin pump—it is for subcutaneous use only 3

Recognize Over-Basalization

• When basal insulin approaches 0.5-1.0 units/kg/day without achieving glycemic targets, add prandial insulin rather than continuing to escalate Lantus 1, 7
• Clinical signals of over-basalization include: basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia, and high glucose variability 1, 7

Injection Site Management

• Rotate injection sites within the same region (abdomen, thigh, or deltoid) to reduce risk of lipodystrophy and localized cutaneous amyloidosis 3
• Do not inject into areas of lipodystrophy, as this can cause erratic absorption and hyperglycemia 1, 3

Expected Clinical Outcomes

• Equivalent or better HbA1c control compared to NPH with significantly less hypoglycemia 4, 5
• Higher treatment satisfaction reported by patients switching to Lantus 4
• More patients achieve HbA1c ≤7.0% without nocturnal hypoglycemia compared to NPH 5
• The long-acting effect provides 24-hour coverage with once-daily dosing, improving adherence 4, 6

Glucagon Prescription

• Prescribe emergency glucagon for all patients at high risk of severe hypoglycemia, particularly those with type 1 diabetes or history of severe hypoglycemic episodes 1, 2