To determine the required volume of U-100 insulin to administer a20-unitdose ofNPH insulin, we use the concentration definition:

U-100 insulinmeans100 units per 1 ml

We need20 units

Using the formula:

Volume (ml)=Dose (units)Concentration (units/ml)\text{Volume (ml)} = \frac{\text{Dose (units)}}{\text{Concentration (units/ml)}}Volume (ml)=Concentration (units/ml)Dose (units)​Volume=20 units100 units/ml=0.2 ml\text{Volume} = \frac{20 \text{ units}}{100 \text{ units/ml}} = 0.2 \text{ ml}Volume=100 units/ml20 units​=0.2 ml

Thus, the correct answer is0.2 ml.

A. 0.02 ml→ Incorrect; this would correspond to only 2 units.

B. 1 ml→ Incorrect; this would correspond to 100 units, far exceeding the prescribed dose.

D. 2 ml→ Incorrect; this would correspond to 200 units, which is incorrect.

Other Answer Choices Explained:References:

PTCB PTCE Exam Content Outline (Pharmaceutical Calculations)

USP <797> Pharmaceutical Compounding—Sterile Preparations

American Pharmacists Association (APhA) Pharmacy Technician Certification Review