I won't go into details, but I suddenly found myself in need of medical services. Luckily there are health care providers, generally just called "healers" or "doctors" no matter the level of expertise or training, just about everywhere. I hopped in the car and within moments was standing in the lobby of one such place. "Living room" might be the more accurate term. I had used this particular healer in the past and knew her reputation was very good. The healer was able to get to me right away and fixed me right up.
There were no forms to fill out, and all she had to do was to check my medical history online (at my own personal medical page- everyone has one that any healer can access- with permission), check for any conditions that might conflict with the treatment she had in mind, and get on with it. She wrote down the name of the medicine she wanted me to use, and I took that "prescription" to a local pharmacist who sold me the medicine and told me how to use it for best effect. Had I not had that piece of paper from the healer, but only remembered the name of the medicine, that would not have changed things at all.
It cost a half an ounce of silver for the treatment, and a quarter ounce for the medicine I will need for a few days. I tipped the healer a bit more as a "thank you" for good service.
Different cases need different levels of expertise, of course. You don't need years of medical school to fix most problems. Obviously if a patient goes to a healer who doesn't feel confident about fixing their problem, they will be referred to someone who can deal with it. The first healer seen would be liable for restitution otherwise.
No one tells the doctors or pharmacists which medications they are allowed to use or sell, or in what amount. There is no centralized "licensing authority", although there are a few certifications available for healers who want them. An incompetent healer won't get certified because their certification service would lose reputation (and customers). Otherwise it is all based on reputation and individual liability. You harm patients and word will get around and you will have trouble attracting new customers no matter how nice your prices. Plus, you would be liable for paying restitution to those you harmed (or their survivors in the worst cases).