For a patient using 3 mL insulin pens containing 100 units/mL, daily dose 0.8 units/kg for 30 days, how many pens are required?

For a patient using 3 mL insulin pens containing 100 units/mL, daily dose 0.8 units/kg for 30 days, how many pens are required?

• A. 7 pens
• B. 6 pens
• C. 5 pens
• D. 8 pens

Answer: (A)

To figure out how many insulin pens are needed, convert the pen’s capacity to units and then scale to the monthly dose. Each pen delivers 3 mL × 100 units/mL = 300 units per pen. The monthly requirement is 0.8 units/kg per day for 30 days, which is 0.8 × 30 = 24 units per kg for the month. Multiply by the patient’s weight in kilograms to get total units: total units = 24 × weight. The number of pens is total units divided by 300, i.e. pens = (24 × weight) / 300 = weight / 12.5. Since you can’t use a fraction of a pen, you round up to whole pens. If seven pens are needed, the weight must be 7 × 12.5 = 87.5 kg (since 87.5 / 12.5 = 7). Without a given weight, the exact number of pens can’t be determined; the formula shows how weight directly sets the required number of pens.

To figure out how many insulin pens are needed, convert the pen’s capacity to units and then scale to the monthly dose. Each pen delivers 3 mL × 100 units/mL = 300 units per pen. The monthly requirement is 0.8 units/kg per day for 30 days, which is 0.8 × 30 = 24 units per kg for the month. Multiply by the patient’s weight in kilograms to get total units: total units = 24 × weight. The number of pens is total units divided by 300, i.e. pens = (24 × weight) / 300 = weight / 12.5. Since you can’t use a fraction of a pen, you round up to whole pens.

If seven pens are needed, the weight must be 7 × 12.5 = 87.5 kg (since 87.5 / 12.5 = 7). Without a given weight, the exact number of pens can’t be determined; the formula shows how weight directly sets the required number of pens.