For 2018, you can only claim medical expenses for a
one year period that must end in 2018. So you may be able to claim some 2017
expenses on your 2018 return, but not from previous years.
You can go back to your previous years returns and
add the expenses from those years, through the CRA or through
ReFILE: https://turbotax.community.intuit.ca/replies/2647992
