For a patient switching from twice-daily NPH to glargine U-100, what dosage adjustment should be made?

When switching a patient from twice-daily NPH (Neutral Protamine Hagedorn) insulin to glargine U-100 (a long-acting insulin), it is standard clinical practice to reduce the total daily dose of insulin. This adjustment is based on the pharmacokinetics and dynamics of the different insulin formulations.

NPH insulin has a peak action and a more variable duration compared to glargine, which has a flatter and more predictable profile. Because glargine is administered once daily and potentially offers better basal coverage, the transition from a two-injection regimen to a once-daily regimen typically involves a dose reduction to account for the different action profiles.

A reduction of approximately 20-30% is commonly recommended when making this switch to avoid the risk of hypoglycemia, as glargine's prolonged action may lead to an increased risk of low blood sugar if the dosage is not adjusted. Therefore, decreasing the dose by 20% is a prudent approach to ensure the patient remains within a safe range and maintains good glycemic control without experiencing adverse effects.