Medical expenses can be claimed as an itemized deduction for U.S. federal income tax purposes to the extent they exceed 7.5% of your adjusted gross income.  You can claim medical expenses for yourself, your spouse, and your dependents.  You deduct the medical expenses in the year you paid for them, regardless of when the medical services were provided.  But you do not necessarily have to be able to claim an exemption on your current year tax return in order to claim medical expenses you paid for a spouse or dependent.  The test is whether the person was your spouse or qualified as your dependent at the time the medical services were provided, or at the time you paid for them.  The following are some examples.

Medical Expenses of a Spouse

If you paid for the medical expenses of your present spouse, who received the medical treatment before you were married, you can deduct those medical expenses because you paid them while you were married.  You can deduct these expenses even if you file separate returns instead of filing jointly.

If you paid medical expenses this year, for your spouse who died last year, you can claim a deduction for those expenses this year, because you were married at the time the medical services were provided.  You can deduct the medical expenses paid for your deceased spouse even if you remarried in the current year and file a joint return with your new spouse.