You deduct medical expenses in the year that you paid them, regardless of when the services were provided. If you paid some of the expenses in 2017, you deduct them on your 2017 tax return, even if they were payments for services that you received in 2016. But any expenses that you paid in 2016 have to go on your 2016 tax return.
You can only deduct medical expenses that were not paid or reimbursed by insurance.
As xmasbaby0 said, for 2016 only the amount over 10% of your AGI (Adjusted Gross Income) is deductible. For 2017 it's the amount over 7.5% of your AGI. In TurboTax you enter your full unreimbursed medical expenses. TurboTax will subtract the 10% or 7.5% of AGI.
