I have not submitted my medical expenses to my HSA account for reimbursement for my 2018 medical expenses. I plan to submit them later in 2019. I expect that I will then receive a 1099-SA for 2019 showing the HSA distributions. Will these distributions be subtracted from my 2019 itemized medical deductions on my 2019 taxes? In which case for 2018, I should include the full amount of my medical expenses for my itemized medical deductions and not subtract the HSA distributions that I have not yet submitted? Is that correct? Or should I subtract them for my 2018 itemized medical deductions on my taxes. I am taking itemized deductions this year.
If you plan to get reimbursed in 2019, don't report them as deductible expenses on your 2018 return.
If you do report them as a deduction, then the reimbursement may become taxable income (a reimbursement of a previous deduction.) It's better to avoid that whole mess and not deduct the expenses now if you know you will get a tax-free reimbursement from an HSA or an insurance company.
Will I receive a 1099-SA in 2019 for the 2018 expenses I submit in 2019? And if I do not deduct medical expenses this year, as you suggest, then in 2019 I will not have to subtract the 1099-SA from medical expenses I may deduct for 2019, correct?
The 1099-SA is issued for withdrawals by calendar year.
Any medical expense is deducted when paid to the provider, not when incurred, whether you pay with cash, or a credit card or loan in your name that you will pay back over time. (For example, if you pay for a $5000 surgery with a credit card to the provider and then pay $100 a month to the credit card issuer, that counts as a $5000 payment of a medical expense. If you pay the provider directly $100 a month, that counts as a series of $100 medical expenses. I can explain why if needed.)
You can never deduct a medical expense that was paid for with tax-free money, and if you deduct an expense and are later reimbursed tax-free, the reimbursement may become taxable, depending on the overall situation.
Now, Turbotax assumes you can't keep track of this yourself, and asks for all medical expenses you paid during the year, and then asks separately about tax-free reimbursements. You would get the exact same result if you only listed non-reimbursed expenses in the first place, but Turbotax wants to do the math for you.
In this case, if you paid the provider in 2018, and reimburse yourself in 2019 from an HSA, then it is technically a 2018 medical expense deduction, and then a 2019 taxable reimbursement. (Or may be a taxable reimbursemen, but that requires a complicated analysis that is is simpler to avoid.) As long as you can keep track yourself and don't need Turbotax to do the math for you, simply ignore the expense on your 2018 return and ignore the reimbursement on your 2019 return.