If a medication dose requires 25 mg and the stock concentration is 50 mg/mL, how many milliliters are needed?

If a medication dose requires 25 mg and the stock concentration is 50 mg/mL, how many milliliters are needed?

• A. 0.5 mL
• B. 0.25 mL
• C. 1 mL
• D. 2 mL

Answer: (A)

Think of how much liquid is needed based on how concentrated the solution is. If the stock is 50 mg per 1 mL, every milliliter contains 50 mg. To get 25 mg, you only need half of that amount, so you’d use 0.5 mL. You can confirm with the calculation: 25 mg ÷ 50 mg/mL = 0.5 mL. The milligrams cancel out, leaving milliliters, and since 25 mg is exactly half of 50 mg, the required volume is half a milliliter.

Think of how much liquid is needed based on how concentrated the solution is. If the stock is 50 mg per 1 mL, every milliliter contains 50 mg. To get 25 mg, you only need half of that amount, so you’d use 0.5 mL. You can confirm with the calculation: 25 mg ÷ 50 mg/mL = 0.5 mL. The milligrams cancel out, leaving milliliters, and since 25 mg is exactly half of 50 mg, the required volume is half a milliliter.