There aren’t any known safety issues with giving a person Narcan when they don’t need it. Narcan doesn’t have an effect on a person who’s sober from opioids. (“Sober” means they don’t have any opioids in their system.)
If you suspect, but aren’t certain, that a person has overdosed on opioids, you should still give them a dose of Narcan. This is because opioid overdose may, in some cases, be fatal if it isn’t treated. In this situation, it’s best to go ahead and give Narcan to this person just in case.
If you have more questions about giving Narcan to someone, talk with your doctor or pharmacist.