The deduction for medical expenses is limited to the amount in excess of 10% of your adjusted gross income (7.5% if you (or your spouse) are over 65 years old. So, for example, if your adjusted gross income is $40,000 and you have $5,000 in medical expenses you would be entitled to an itemized deduction of $1,000 (40,000 x 10% = 4,000 5,000-4,000=1,000).