DavidCPA is the resident Tax expert. But to deduct medical expenses you have to itemize your deductions on Schedule A rather than take the standard deduction. If are deducting your mortgage interest payments, then you are already filing Schedule A.
After this tax year of 2012, the percentage goes up from 7.5 of your Adjusted Gross income (AGI) to 10% of what you need to exceed to take the deductions ((for taxpayers 65 and older, it stays at 7.5% through 2016). Here is a link to an IRS tax sheet that spells it out topic 502
Each year the IRS updates a full publication on taking this deduction. Here is the most current one
irs pub med deductions with lots of detail
The key is to start now gathering all this info and use the topic list and the extensive lists in the publication to be sure you do not miss any. Each year, I rack up about $15,000 in deductions (it'd be more but my BC/BS has a $6,000 catastrophe limit that I easily hit) although I don't get to deduct all of it, it does help.
charm