Converting from 70/30 to NPH Insulin in Hospitalized Patients with Hyperglycemia
Recommended Starting NPH Dose
Start with 26 units of NPH insulin given as a split dose: 18 units in the morning and 8 units at bedtime (approximately 80% of the previous 70/30 total daily dose, distributed as 2/3 morning and 1/3 evening). 1
Rationale for Dose Conversion
When converting from premixed 70/30 insulin to NPH, the American Diabetes Association recommends using 80% of the current total daily dose to reduce hypoglycemia risk during the transition 1
The 70/30 insulin contains 70% intermediate-acting (NPH-like) and 30% rapid-acting components, so the patient was receiving approximately 23 units of basal coverage from their previous 33-unit dose 1
Splitting the NPH dose into twice-daily administration (2/3 morning, 1/3 evening) provides better 24-hour glucose coverage than once-daily dosing, particularly for patients with persistent hyperglycemia in the 200s mg/dL range 1
Additional Prandial Coverage Needed
Since the patient is now hospitalized and eating regular meals, add rapid-acting insulin at mealtimes starting with 4 units before each meal or 10% of the basal dose 1
This prandial insulin replaces the rapid-acting component that was previously provided by the 70/30 formulation (approximately 10 units total daily) 1
For the largest meal or meal with greatest postprandial glucose excursion, consider starting with the full prandial dose first, then expanding to other meals if needed 1
Titration Strategy
Increase NPH by 2 units every 2-3 days if fasting glucose remains >180 mg/dL, targeting inpatient goals of <110 mg/dL fasting and 110-180 mg/dL throughout the day 1, 2
If hypoglycemia occurs (glucose <70 mg/dL), reduce the corresponding NPH dose by 10-20% 1
Adjust prandial insulin by 1-2 units or 10-15% twice weekly based on pre-meal and 2-hour postprandial glucose values 1
Important Clinical Considerations
Monitor glucose every 4-6 hours initially to assess adequacy of the new regimen and identify patterns of hyper- or hypoglycemia 1, 2
The patient's persistent hyperglycemia in the 200s suggests they were undertreated on their home regimen, so aggressive titration upward may be necessary after the initial conservative conversion 1
If the patient has renal or hepatic impairment, is elderly, frail, or has other conditions increasing hypoglycemia risk, consider starting with an even lower dose (reduce by an additional 10-20%) 1
For patients with marked obesity, active infection, or open wounds, the starting dose may need to be higher (add 0.2 units/kg to the basal component) 2
Common Pitfalls to Avoid
Do not use a 1:1 conversion from 70/30 to NPH—this will provide excessive basal insulin and increase hypoglycemia risk since 70/30 contains both basal and prandial components 1
Avoid giving all NPH at bedtime only, as this will not adequately cover daytime hyperglycemia in a patient with glucose readings in the 200s 1
Ensure the patient continues to receive basal insulin even if made NPO—reduce the dose but do not discontinue, especially if there is any possibility of type 1 diabetes 1
Watch for overbasalization (basal dose >0.5 units/kg/day, elevated bedtime-to-morning differential, or frequent hypoglycemia), which signals need for more prandial and less basal insulin 1