Medical expenses are an itemized deduction, which means you have to have specific expenses in order to deduct them. There is no standard amount you can deduct.
What you might be referring to is the threshold for being able to deduct these expenses. You can only deduct medical expenses that are in excess of 10% (7.5% if 65 or older) of your adjusted gross income.
Example: Your AGI is $50,000 and you have $7,000 in medical expenses for 2016. This means your threshold is $5,000 (10% of $50,000) and you can only deduct the amount over this threshold ($2,000). This $2,000 would be an itemized deduction for you.
But, you still need to be able to itemize your deductions in order to benefit from medical expenses - i.e you need to have more total itemized deductions than the standard deduction.
For 2016, the standard deduction amounts are: $6,300 (single), $12600 (married filing jointly), or $9,300 (head of household). Every taxpayer starts off with these amounts in deductions as a "base" deduction from income that the IRS allows. So, you will need to have total itemized deductions (things like medical expenses, mortgage interest, property taxes, charitable donations) greater than these amounts before you start to see additional tax benefit from itemizing your deductions.
