Former US surgeon general Jerome Adams was stuck with an eye-watering medical bill of nearly $5,000 after being treated for a simple case of dehydration following an overnight stay at an Arizona hospital last January.

Now he's calling for reforms to the country's market-based health care system, including greater transparency around costs and an independent arbitration process -- while using his bully pulpit to speak out for the 100 million Americans saddled with medical debt.

Although the rate of uninsured Americans has been declining in recent years, The Commonwealth Fund estimates that 43 percent of working-age adults are "underinsured," which limits their access to care and leaves many just one major catastrophe away from financial ruin.

"I was out at the Society of Critical Care Medicine meeting in Phoenix, Arizona, and like literally thousands of tourists visiting that area, I decided that I would go and hike up Camelback Mountain," the 49-year-old, now at Purdue University, told AFP.

He took along a bottle of water, more than enough, he thought, for a 60-degree Fahrenheit (16 degrees Celsius) day.

But by the time he was heading out for dinner, he started feeling dizzy and lightheaded -- and his fellow doctors advised him it was best to get it checked out, especially as a middle-aged Black man at higher risk of cardiovascular complications.

"We called an ambulance because I was out of town. I got IV fluids on the way. And by the time I got there, it was pretty clear that it was dehydration," he said in an interview from Indianapolis.

He took medics' advice and stayed overnight, and two months later received a bill for $4,800 despite being insured. Threats of being sent to collections agencies soon followed.

Adams said he was well aware his situation was all too common in a country where nearly 66 percent of all bankruptcies are directly tied to medical expenses.

But as a Black physician who walked a tightrope to advocate for racial justice in health care -- both as Donald Trump's surgeon general and before that as head of Indiana's health department under Mike Pence -- Adams said he could be a champion for others.

"My complaint isn't about me personally, because I will be okay -- but I do have a voice," he insisted. He has kept busy posting to his nearly 90,000 X followers about other cases, such as a mother of premature quadruplets handed a bill of $4 million.

  Market reforms 

 While progressives like Vermont Senator Bernie Sanders have proposed eliminating private health insurance altogether, Adams says that's not realistic given that too many players profit from the status quo.

Rather, he advocates for a set of reforms that work to regulate the free market, just as the Affordable Care Act, better known as Obamacare, did in the 2010s.

First, more transparency: "You can't have a market without transparency and accountability -- and right now, if I went to a car dealer, they would have to tell me how much the car costs."

Second, he says, there needs to be an arbitration process where the hospitals that provide the care -- the Mayo Clinic in his particular case -- aren't given full reign, creating situations where patients have no recourse to contest their mega bills. Mayo did not provide a requested comment to AFP.

Third, while Obamacare helped bring coverage to tens of millions of Americans, it partly did so by incentivizing employers to provide workers with plans that cost them less -- but also pay out much less, said Adams.

People in these plans -- including Adams himself -- can make contributions to tax-free spending accounts to offset some of their risk. But if a health incident occurs early on in the year, they may not have enough stashed away -- and in such cases, legislation should be passed requiring insurers to foot a larger portion, he said.

Ultimately, he said, all Americans should have access to preventative and emergency care without financial barriers holding them back.

For Adams, who grew up with severe asthma and saw repeated trips to the hospital as a child because his parents couldn't afford his medications, the policies he's advocated for during his career have always been personal too.

"There's a lot of trade-offs that we have here," he said of American health care. "But we've got to ask ourselves, at what point even in a capitalistic system is enough, enough?"