Do I need to report medical expense reimbursements?
If the expense and reimbursement both happened in 2016, then yes.
You can either subtract the reimbursement from the expenses you originally paid and enter the new expense amount, or enter it after you've finished entering all of your medical expenses. Either way, the reimbursement simply reduces your medical expense deduction by that amount.
But what if you got a 2016 reimbursement for medical expenses you paid in 2015 or a prior year? If you were able to deduct medical expenses for that prior year, report the reimbursement (or the amount of the medical deduction you got in the prior year, whichever is less) on your 2016 taxes.
If you weren't able to deduct medical expenses for that prior year, then don't report the reimbursement.
For more information, see Where do I enter my medical expenses?