Denise Revel had a history of developing blood clots, so in 2011, when her leg grew painfully swollen and hot to the touch, she knew what to do. She headed for the emergency room.
She recovered from the clot but could not pay the medical bill. Working as a fitness instructor, she had no health insurance. “I’ve always been financially challenged,” said Ms. Revel, 62, who lives with her daughter in Stockbridge, Ga. “I was a single parent raising two children.”