Expensive mistakes on medical bills are hard for most of us to detect, because the bills are written in a mysterious language that we don't speak.
But eight out of 10 medical bills have mistakes on them, according to Medical Billing Advocates of America.
What if you could hire somebody to translate your bills and then do battle for you?
Turns out, you can. And it might not even cost you anything.
Artist Cynthia Kulp thought being diagnosed with breast cancer was the worst thing that could happen to her. But, then, the hospital where she received her breast cancer treatment overcharged her.
"To have to fight a hospital going through cancer treatment, overcharging me, they have to be the lowest of the low," Kulp said.
Before her lumpectomy, she said, the hospital told her the operation would cost $5,000. Instead, she got a bill for $12,700, right in the middle of her course of chemotherapy.
"You can barely function, you can barely get out of bed," she said. "How can you fight hospitals?"
So she hired Holly Wallack, a medical billing advocate, to help. Wallack found all kinds of errors on Kulp's bill, such as:
Mismatches. These are drugs that appeared on the medical bill, even though they weren't listed in the medical records.
Double charges. The hospital charged Kulp for two "first" hours in the recovery room. So Wallack asked, "How many 'first' hours do you get? Last I heard, there was only one, then he was very happy to take that charge off."
Inflated charges. The hospital billed $192 for a postoperative support bra that Wallack found on the Internet for $19 -- a tenth of the cost.
"That was one morning in one operating room in one hospital in one little town in the country," she said. "If you extrapolate that out to what's going on every day, it's mind boggling."
Here are a few other billing mistakes to watch out for:
Billing for things that ought to be included. That's like paying for the value meal and also being charged separately for the sides.
Misplaced decimals. ABC News saw one bill that read $874 for an $87.40 medication, for example.
Fat fingers. These are extra line items caused by clerical clumsiness. A medication might be listed seven times in a row, even though it's only supposed to be given four times a day.
"Our medical situation in the U.S. is seriously broken, and it needs to be fixed," Wallack said. "And I don't know how to fix it. I'm fixing it one bill at a time."
Wallack negotiated Kulp's bill from $12,700 down to $5,800, a $7,000 savings. "It was like a miracle that we found her," Kulp said.
There was another miracle, too. Despite having one of the most aggressive, devastating forms of the disease, Kulp fought off the breast cancer and won.
Medical billing advocates like Wallack either charge an hourly fee, ranging from $60 to $175, or they work on a contingency basis, earning a commission of 15 percent to 35 percent of the amount they save you.
If you do it that way, you don't pay a dime unless they lower your bill, which makes them highly motivated to do just that.
It's a little tricky to find a medical billing advocate, because they go by many names such as claims assistance professional, medical claims professional or health care claims advocate.