What percent of collections does a collections agency get for a medical bill collection?

This depends on the collection agency, but the age of the account, the location of the debt (that regulate collection laws by the state), play a big role. The older the account the higher the percentage that goes to the collection agency

the percentage is negotiated between the agency and the client(this is a fact, part of a previous job).ive seen between 10% and some as high as 40%.

which if you have a bill from an agency, it really isn't any f your business how much they get, you should be worried abour negotiations.