It's complicated. From google:

* You must pay the premiums with after-tax money.

* Your total qualified, unreimbursed medical and dental expenses (including premiums and costs like co-pays, deductibles, prescription medications, etc.) must exceed 7.5% of your Adjusted Gross Income (AGI).

* You can only deduct the amount of expenses that exceeds this 7.5% threshold.

* You must choose to itemize deductions instead of taking the standard deduction.

Most taxpayers use the standard deduction as it is often larger than their total itemized deductions.