I am not sure since FSA is pre-tax and already deducted, if have to subtract the FSA amount from my total medical expense, which is much higher than the FSA amount. And medical expenses are divided into categories, so I am not sure where/how I am supposed to subtract it if needed. Thank you.
Yes, you can deduct the amounts that you paid for medical expenses that are beyond the amounts paid for by your FSA.
You can't deduct medical expenses that were paid with a health savings account (HSA), medical savings account (MSA), flexible spending account (FSA) or health reimbursement account (HRA). These are all pre-tax accounts, and you can't deduct medical expenses that were paid with a pre-tax account.
Subtract the amounts paid from your FSA from your total medical expenses and deduct the remainder. How you categorize the expense that you deduct isn't really important, as long as you aren't double deducting.
[Edit 01/25/18 11:11 AM]
Yes, you can deduct the amounts that you paid for medical expenses that are beyond the amounts paid for by your FSA.
You can't deduct medical expenses that were paid with a health savings account (HSA), medical savings account (MSA), flexible spending account (FSA) or health reimbursement account (HRA). These are all pre-tax accounts, and you can't deduct medical expenses that were paid with a pre-tax account.
Subtract the amounts paid from your FSA from your total medical expenses and deduct the remainder. How you categorize the expense that you deduct isn't really important, as long as you aren't double deducting.
[Edit 01/25/18 11:11 AM]
@hj86 , please see my edited answer for an FSA rather than an HSA.