The nurse retrieves hydromorphone "4 mg/mL" from the electronic medication system, for a patient who is receiving hydromorphone 3 mg IM every 6 hours PRN for severe pain. How many mL should the nurse administer to the patient? (Enter the numerical value only. If rounding is required, round to the nearest tenth.) The nurse needs to administer hydromorphone 3 mg to the patient. The concentration of the hydromorphone solution is 4 mg/mL. To find out how many mL the nurse should administer, we can use the formula: