A medication is dosed at 0.5 mg/kg. The patient weighs 12 kg. What is the dose?

A medication is dosed at 0.5 mg/kg. The patient weighs 12 kg. What is the dose?

• A. 4 mg
• B. 5 mg
• C. 8 mg
• D. 6 mg

Answer: (D)

The concept here is that the total dose in milligrams comes from multiplying the dose per kilogram by the patient’s weight, so the units mg/kg times kg cancel to give milligrams. So you take 0.5 mg per kilogram and multiply by 12 kilograms: 0.5 × 12 = 6. That yields 6 mg. If you check the other numbers by thinking about weight, 4 mg would come from a weight of 8 kg (0.5 mg/kg × 8 kg = 4 mg), 5 mg from 10 kg, and 8 mg from 16 kg. Since the patient weighs 12 kg, the correct total dose is 6 mg.

The concept here is that the total dose in milligrams comes from multiplying the dose per kilogram by the patient’s weight, so the units mg/kg times kg cancel to give milligrams. So you take 0.5 mg per kilogram and multiply by 12 kilograms: 0.5 × 12 = 6. That yields 6 mg.

If you check the other numbers by thinking about weight, 4 mg would come from a weight of 8 kg (0.5 mg/kg × 8 kg = 4 mg), 5 mg from 10 kg, and 8 mg from 16 kg. Since the patient weighs 12 kg, the correct total dose is 6 mg.