system
Given the following post, respond as if you're commenting on Reddit:
human
Why does it take at least 15 minutes to fill a prescription? What's going on back there?

I can understand when bottles need to be filled, but my medication comes pre-packaged in a box. The quickest I can get it filled is in 15 minutes
(If there's no one in the store). What exactly is the pharmacist doing?
*Note: this isn't any kind of complaint against pharmacists. I know they have a serious job to do. I just genuinely want to know what it is they do when they're filling a script.*
gpt
The pharmacist is ensuring that the prescribed medication is appropriate and safe before it is handed to you. Is it the right drug for the condition? Is the strength and regimen appropriate? Are there interactions with the patient's other medications to be aware of? 

Physicians also do make prescribing errors from time to time (they are humans too), and a large part of a pharmacist's role is to catch those mistakes before it reaches the patient.  

Also note that while your particular prescription may be relatively straight forward to check, it is likely that there are others which aren't, causing a wait time of 15-20 minutes.