You can estimate it based upon your method above.
But be sure to retain all of your support should the IRS ever request additional support.
As long as the expenses are all deductible medical expenses, you should be fine.
Here is some additional information on deductible medical expenses for your reference.
Article outlining medical expenses
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
