Sometimes, it might seem like your doctor is relying on years of education and experience.
Other times, you might be convinced he's making it up as he goes.
In reality, most doctors follow the guidelines issued by the major medical associations -- and that means some of the biggest decisions he makes about you and your health are based on badly biased information.
Treatment guidelines are routinely written by "experts" with a direct financial stake in the outcome -- and now, a new study finds a massive chain of conflicts in the guidelines written for diabetes treatments and cholesterol control.
Since these just so happen to be two of the most medicated (not to mention over-medicated) conditions in the country, is anyone really surprised?
There have been 288 "experts" on the 14 cholesterol and diabetes panels that have met in the United States and Canada over the past decade, and researchers say 52 percent of them had conflicts of interest such as financial ties to the drug industry.
Even worse, they found those conflicts among 11 percent of the panelists who claimed they were free and clear.
And of course, you can't really stack a deck without putting some of your best cards on top -- so half of all chairs of the guideline-writing committees had conflicts.
The panels were convened by organizations including private ones like the American Diabetes Association and American Heart Association as well as government groups such as the U.S. Preventive Services Task Force.
But when you break it down, only 16 percent of the members of government-sponsored panels had conflicts, versus 69 percent of those convened by nongovernmental groups.
What's more, five of the groups in the study didn't even require conflict disclosures -- and the U.S. Preventive Services Task Force won't reveal its own without a Freedom of Information Act request.
That's one of those things that make it look like you're hiding something... even if you're not.
This isn't limited to cholesterol and diabetes panels -- not by a longshot.
Earlier this year, researchers examined 17 critical guidelines from the American Heart Association and American College of Cardiology that were issued between 2003 and 2008, and found that 56 percent of the 498 people who helped write them had conflicts of interest... including 81 percent of those who led the groups.
Put it all together, and it's pretty clear why you can't leave your doctor's office without yet another prescription: The deck was stacked against you long before you even walked through the door.