To deliver 25 mg using a 25 mg/mL stock, what is the volume required?

To deliver 25 mg using a 25 mg/mL stock, what is the volume required?

• A. 0.5 mL
• B. 2 mL
• C. 1 mL
• D. 5 mL

Answer: (C)

Volume to deliver comes from dose divided by concentration. A stock of 25 mg/mL means there are 25 mg in every 1 mL. To get 25 mg, you need 25 mg ÷ 25 mg/mL = 1 mL. This approach also makes intuitive sense: half a milliliter would deliver 12.5 mg, while twice that amount (2 mL) would deliver 50 mg, and 5 mL would deliver 125 mg. So the required volume is 1 mL.

Volume to deliver comes from dose divided by concentration. A stock of 25 mg/mL means there are 25 mg in every 1 mL. To get 25 mg, you need 25 mg ÷ 25 mg/mL = 1 mL. This approach also makes intuitive sense: half a milliliter would deliver 12.5 mg, while twice that amount (2 mL) would deliver 50 mg, and 5 mL would deliver 125 mg. So the required volume is 1 mL.