FSA and HSA withdrawal rules specify what can be bought with FSA/HSA funds. Most people use their HSA/FSA money to pay for health care insurance premiums, urgent care bills, doctor copays and prescription medications. Funds can also be used for over-the-counter medications, rapid tests and masks, mobility tools and more.
If someone exercises to prevent or treat a range of medical conditions, related fees like gym memberships, classes and personal training costs can become HSA/FSA eligible, too! But for a person to pay for those things from their HSA/FSA account, a doctor or other licensed provider needs to write them a Letter of Medical Necessity detailing how exercise treats their specific medical condition, justifying the related costs as medically necessary. With that letter, they can submit it and any (new) exercise receipts to their HSA/FSA administrator for reimbursement. Purchases made before the letter was issued do not qualify for reimbursement.