Threshold
Medical expenses are deductible only to the extent they exceed 7.5% of adjusted gross income. For most middle-income filers, this threshold blocks the deduction entirely. For self-employed taxpayers, the above-the-line self-employed health insurance deduction is far more valuable for premiums.
Qualifying expenses
Doctors, dentists, chiropractors, eyeglasses, contact lenses, hearing aids, prescription drugs (over-the-counter only with a prescription), insulin, hospital care, qualified long-term care services, transportation primarily for and essential to medical care, and home modifications recommended by a physician.
Mileage
Medical-related mileage is deductible at the IRS medical rate (21¢ per mile for 2024). Plus parking and tolls. Track mileage to and from doctor visits, pharmacy trips, and any travel essential to medical care.
HSA, FSA, HRA exclusions
Expenses paid by an HSA, FSA, HRA, or other tax-favored account are not separately deductible — they are already excluded from income (HSA, FSA) or paid by the employer (HRA). Only your true out-of-pocket spend qualifies for the Schedule A deduction.
Long-term care insurance
Qualified long-term care insurance premiums are deductible up to age-based dollar caps that increase each year. Self-employed individuals may instead use the self-employed health insurance deduction for these premiums (subject to the same age-based caps).
Where this fits in the larger Schedule C picture
Schedule C has more than two dozen named expense lines plus an "Other expenses" catch-all. For most small businesses, four or five lines drive the bulk of the deduction total — vehicle, home office, depreciation, contract labor or wages, and supplies — and the remaining lines individually contribute small amounts that nevertheless add up. Treating each named line as a recurring decision rather than an afterthought, and revisiting the categories each January, often surfaces $2,000–$5,000 in additional legitimate deductions that a less disciplined process would have missed entirely.
Documentation that survives an exam
An IRS examination of this deduction will request three things: proof of payment (bank or card statement), proof of the underlying transaction (invoice or receipt), and proof of business purpose (a contemporaneous note or calendar entry). The first two are usually trivial to produce; the third is where most filers fall short. Capturing business purpose at the moment of the expense — a one-line note in your bookkeeping software or a category and memo on the receipt-capture app — converts a generic charge into a documented deduction that will withstand scrutiny three to six years later when memory has faded.