A medication order is 0.5 mg/kg for a 40 kg patient. What is the total dose in milligrams?

A medication order is 0.5 mg/kg for a 40 kg patient. What is the total dose in milligrams?

• A. 10 mg
• B. 20 mg
• C. 30 mg
• D. 40 mg

Answer: (B)

Dose calculation from mg/kg requires multiplying the prescribed milligrams per kilogram by the patient’s weight in kilograms. Here, 0.5 mg per kg for a 40 kg patient means 0.5 × 40. Doing the math gives 20 mg. The kg units cancel, leaving milligrams. So the total dose is 20 mg. The other numbers would correspond to different per-kilogram doses (for example, 10 mg would come from 0.25 mg/kg, 30 mg from 0.75 mg/kg, and 40 mg from 1 mg/kg), which aren’t the prescribed amount.

Dose calculation from mg/kg requires multiplying the prescribed milligrams per kilogram by the patient’s weight in kilograms. Here, 0.5 mg per kg for a 40 kg patient means 0.5 × 40. Doing the math gives 20 mg. The kg units cancel, leaving milligrams. So the total dose is 20 mg. The other numbers would correspond to different per-kilogram doses (for example, 10 mg would come from 0.25 mg/kg, 30 mg from 0.75 mg/kg, and 40 mg from 1 mg/kg), which aren’t the prescribed amount.