A liquid medication is 2 mg/mL; the order is 5 mg. How many mL should you administer?

• A. 1.0 mL
• B. 5.0 mL
• C. 3.0 mL
• D. 2.5 mL

Answer: (D)

To find how many milliliters to give when you know the strength is 2 mg per 1 mL and the order is 5 mg, you convert the dose to volume using the concentration. Since 1 mL contains 2 mg, the volume needed for 5 mg is 5 mg × (1 mL / 2 mg) = 2.5 mL. So you would administer 2.5 mL. This also matches the idea that 2 mL would provide 4 mg and 3 mL would provide 6 mg, so 2.5 mL gives the exact 5 mg dose. Use a syringe capable of measuring 2.5 mL accurately.