Can I use my FSA in México?
If you're traveling to Mexico and need to access medical services while there, you may be able to submit for reimbursement when you return to the USA. The medical services must be considered legal within the U.S. to qualify for reimbursement. Hold on to any receipts from medical services you had while abroad, and submit these to your FSA administrator. It's best to contact your FSA administrator about eligibility (if you can also before you leave) and if you're not entirely sure about what's covered.
If you buy prescription drugs while abroad, the IRS mentions the following: "In general, you can't include in your medical expenses the cost of a prescribed drug brought in (or ordered shipped) from another country. You can only include the cost of a drug that was imported legally. For example, you can include the cost of a prescribed drug the Food and Drug Administration announces can be legally imported by individuals."