> diabetes patients test their own blood. If they need more insulin, why does a doctor have to prescribe it

In many states (California is one) you can by certain brands of insulin OTC. The limitation is more a decision of the manufacturer than it is codified into law. Pharmaceutical companies are well known for milking their patents as long as they can and then lobbying hard for OTC status as soon as the end date on their patent is coming up. This gives them the opportunity to continue to push their brand and squashes any competitors who are still behind the counter.

You need look no further than allergy medications for an example. Claritin and Allegra were the biggest brand names in prescription allergy medications just a few years ago. But as Claritin's patent protection period was ending, its makers pushed hard to go OTC. And they did. The result is that Claritin dominates the OTC allergy medication category while Allegra is no longer covered by insurance plans because an OTC alternative is available. It's easy to guess what this did to Allegra's market share.

> There are lots of conditions where it is easy for the individual to maintain their own medications

Maintain is the key word here. OTC availability is only half the story. Your comment makes the assumption that someone knows that they're developing some sort of condition, say diabetes, in the same way they know they're coming down with a cold. How do you know you're becoming diabetic without a doctor's examination and follow up? Are you just going to know think one day that "Hey, maybe I'll google why I feel tired all the time and have been bruising easily lately..."

I know that the medical system is under a lot of fire these days and it's everyone's favorite axe to grind, but some good reasons that prescription control is necessary is to (1) control easily abused substances (this means narcotics as well as antibiotics, though the litigious culture here in the US is quickly rendering traditional antibiotics useless) and, probably most importantly, (2) maintain communication with your healthcare provider. Doctors use prescriptions in order to monitor your compliance and require (at minimum) annual visits so they can check up on you, even if it is only for 5 or 10 minutes. Maybe that decrease in energy is a side effect, or even that occasional but not cold related cough. Your doctor will recognize this and will be able to suggest changes. You probably had no idea a cough was a related side effect. Even if you did, did you keep up on any of the literature for the class of drugs you're taking in the past year? I doubt it. You have better things to do with your time.

> Doctors know a lot, but all doctors don't know everything about every medical condition.

You're right about that. But that's why we have a system of specialists. Even a less than average doctor will refer you up and down that chain until you're dead, out of money, fixed, or have found a way to live with it. It's like throwing a reverse exception where it gets passed from the most general to the most specific handler. Or a search tree where the root is the most general case and the leaf nodes the most specific. Of course it could be more efficient: science could be more advanced, doctors could be smarter, insurance companies more willing to pay, and patients less litigious. But the way doctors handle medical cases has evolved this way because it can solve the most common cases the fastest. And the rare cases, the exceptions? Well, they're rare and the exceptions.

The reason you see so many cases of patients out diagnosing doctors on TV is exactly because they're the rare, man-bites-dog kind of story. How many lottery losers do you see on the nightly news? Safely landing planes? How about stories about cars not piling up in bad weather? My advice to you (though you don't want it) is to stop watching TV. Or at least, stop watching TV and then using what little information is conveyed to make generalizations about the world and how society should be run.

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What became obvious to me from reading your comments is that you don't know what you don't know and that you assume that what you don't know is trivial. There is an unprecedented wealth of information at our fingertips. That's a cliche. But no number of articles read on Wikipedia, no number of Google searches, or stays at a Holiday Inn Express can replace the actual practice of medicine.