A medication is ordered as 0.25 mg/mL. The prescribed dose is 2 mg. How many milliliters should be administered?

A medication is ordered as 0.25 mg/mL. The prescribed dose is 2 mg. How many milliliters should be administered?

• A. 8 mL
• B. 4 mL
• C. 10 mL
• D. 12 mL

Answer: (A)

When you need a certain dose from a solution with a given concentration, use the relationship: volume = dose ÷ concentration. The dose is 2 mg and the concentration is 0.25 mg per mL. So, 2 ÷ 0.25 = 8. This means you should administer 8 mL. You can confirm by checking: 8 mL × 0.25 mg/mL = 2 mg. Delivering less would give less than the desired dose, and more would give more than the dose required, so 8 mL is the exact amount.

When you need a certain dose from a solution with a given concentration, use the relationship: volume = dose ÷ concentration. The dose is 2 mg and the concentration is 0.25 mg per mL. So, 2 ÷ 0.25 = 8. This means you should administer 8 mL. You can confirm by checking: 8 mL × 0.25 mg/mL = 2 mg. Delivering less would give less than the desired dose, and more would give more than the dose required, so 8 mL is the exact amount.