A 9 kg baby is ordered 0.5 mg/kg dose. The stock concentration is 0.1 mg/mL. How many mL?

• A. 4.5 mL
• B. 9 mL
• C. 45 mL
• D. 0.45 mL

Answer: (C)

The main concept is turning a weight-based dose into a volume using the medicine’s concentration. Start by finding the total dose in milligrams: 9 kg × 0.5 mg/kg = 4.5 mg. Then convert that mass to volume with the stock concentration: 0.1 mg per mL means every milliliter has 0.1 mg. To supply 4.5 mg, you need 4.5 mg ÷ 0.1 mg/mL = 45 mL. So the required amount is 45 mL. If a different number appears, check for decimal or unit mix-ups (for example, using a concentration of 1 mg/mL would give 4.5 mL instead).