I did it recently for 2010-2019. I had Quicken records of our medical costs from 2010 to 2019, EOBs for all those years and many receipts (but not for all EOB amounts due). In some cases where I had negotiated a discount with the provider/hospital for an additional discount for immediate payment I used that lower amount that I actually paid rather than the EOB. Total was about $18k so about $2k a year.
I have a 1-2" thick file of a memo, Excel printout and EOBs and receipts in case the IRS ever asks.... but I doubt that they ever will... I think they have bigger fish to fry.