When Barbara Retkowski went to a Cape Coral, Florida, health clinic in August to treat a blood condition, she figured the center would bill her insurance company. Instead, it demanded payment upfront.Earlier in the year, another clinic insisted she pay her entire remaining insurance deductible for the year -- more than $1,000 -- before the doctor would even see her.“I was surprised and frustrated,” Retkowski, a 59-year-old retiree, said in an interview. “I had to pull money out of my savings.”The practice of upfront payment for non-emergency care has been spreading in the U.S. as deductibles rise