If I claimed medical expenses last year(s) but it was under the 3% threshold of income, can I claim it this year to get to that 3% threshold of income this year?

As per our TurboTax article How to Deduct Your Medical Expenses CRA allows you to use any 12-month period of expenses that is most advantageous to your situation, provided it ends in the tax year. You cannot claim a medical expense this year that you have claimed in the previous returns. You have to use the same start and end date for all members of the family. This allows you to claim those medical expenses you couldn’t claim last year, as long as the last date ends in the tax year.

Thank you for using TurboTax.