Medical Grade 20 mmHg to 30 mmHg and 30 mmHg to 40 mmHg Compression stockings of 20 mmHg or higher need to be prescribed by a physician. They are used for the treatment of various medical conditions, and should be used under the supervision of a doctor. The prescription for them needs to be renewed on an annual basis.

In 2026, you generally do not need a legal prescription to purchase 20–30 mmHg (millimeters of mercury) compression socks; they are available over-the-counter (OTC) at medical supply stores, pharmacies, and online retailers. However, this level of pressure is classified as "Firm Medical Grade" and is often the threshold where medical supervision is strongly advised. While you can buy them freely, many pharmacies will ask if a doctor has recommended them, as 20–30 mmHg is used to treat more significant conditions like chronic venous insufficiency, moderate edema, or post-sclerotherapy recovery. If you have underlying conditions like peripheral artery disease (PAD) or advanced diabetes, wearing firm compression without medical advice can be dangerous. For most travelers looking to prevent "economy class syndrome" (DVT) during long flights, a lower 15–20 mmHg "moderate" compression is usually sufficient. If you are stepping up to the 20–30 mmHg level, a consultation with a physician is the safest next step to ensure the pressure is appropriate for your specific circulatory health.