Can I deduct medical, dental, and vision expenses?
You can if you itemize and the total expenses for you, your spouse, and your dependents exceed 10% of your adjusted gross income (7.5% if you're 65 or older as of December 31, 2016). The deduction is limited to the expenses above and beyond this amount.
For example, if you're 48 years old with an AGI of $50,000 and you incurred $5,900 in medical and dental expenses last year, you could deduct $900 (the amount in excess of 10% of your AGI, or $5,000), assuming you're itemizing.
You won't be able to deduct your expenses on your federal return if you're taking the standard deduction, which about 2/3 of all taxpayers do.
However, don't let that stop you from entering all your medical-, dental-, and vision-related expenses anyway. Some states will still let you deduct these expenses even if you weren't able to deduct them on your federal return.