Compression therapy is the use of graduated-pressure garments to support healthy blood flow in the legs. A graduated compression stocking applies its strongest pressure at the ankle and decreases gradually up the leg, which helps the veins and calf muscles move blood back toward the heart against gravity. It is one of the most established treatments in venous care, used both on its own and alongside procedures like sclerotherapy.

The pressure is measured in millimeters of mercury, written as mmHg, and expressed as a range: 15-20 mmHg, 20-30 mmHg, and so on. The range describes the pressure at the ankle, where compression is highest. A higher number means firmer compression, not a better garment; the right level depends on your symptoms and, above 20-30 mmHg, on a clinician's assessment.

How graduated compression works

Veins in the leg carry blood upward through a series of one-way valves. When those valves weaken, blood pools in the lower leg, which produces the aching, heaviness, and swelling that many people notice by the end of the day. Graduated compression narrows the vein slightly and supports the valves, so each contraction of the calf muscle moves blood more efficiently. Because the pressure decreases as it moves up the leg, the flow is encouraged in one direction rather than being restricted.

This is what separates medical compression from a snug athletic sock. The compression is calibrated and consistent across the length of the garment, and it is knit to hold that calibration through repeated wear and washing.

Compression levels

• 8-15 mmHg - the lightest level, for general leg comfort and mild end-of-day fatigue.
• 15-20 mmHg - light, entry-level compression. Relieves tired, aching, heavy legs, eases mild to moderate spider and varicose veins and mild swelling, and supports travel and long periods of sitting or standing.
• 20-30 mmHg - the most commonly prescribed level. Manages moderate varicose veins, moderate leg swelling, and early chronic venous insufficiency, and supports recovery after vein procedures.
• 30-40 mmHg - firm compression for more advanced venous insufficiency, significant swelling, and post-thrombotic symptoms. Typically prescribed.
• 40-50 mmHg - the firmest level, used for severe venous disease under clinical supervision.

Levels at or above 20-30 mmHg are generally recommended by a clinician, who will also confirm that compression is appropriate for you. Compression is not suitable for everyone. Reduced arterial circulation, in particular, needs to be ruled out before firm compression is worn.

Who compression is for

People wear compression for a wide range of reasons. Some have been diagnosed with varicose veins or chronic venous insufficiency and are managing symptoms long term. Others are recovering from a vein procedure and wearing compression for a defined period. Many wear it because their work keeps them on their feet or seated for long stretches, or because they are pregnant, or because they fly frequently and want to reduce swelling and clot risk on long flights.

Choosing a garment

Once you know your compression level, three things shape the choice: style, fabric, and fit. Knee highs are the most commonly worn style, since most venous symptoms occur below the knee. Thigh highs and pantyhose extend coverage when swelling continues above the knee. Fabric ranges from ultra-sheer hosiery that looks like everyday nylons to soft opaque knits and ribbed styles designed to look like regular socks.

Fit is the part that decides whether compression works. A garment sized from accurate ankle and calf measurements delivers the pressure it was calibrated for; one that is too large loses that pressure, and one that is too small becomes uncomfortable enough to go unworn. Every product page on this site carries its own size chart, and our measuring guide walks through taking the measurements at home.

Wearing and caring for compression

• Put them on in the morning - before swelling accumulates, ideally before getting out of bed.
• Wear them daily - consistency is what produces results; occasional wear does little.
• Wash after each wear - body oils and residue break down elastic fibers over time.
• Replace every three to six months - compression garments lose calibrated pressure with use, even when they still look intact.
• Use a donning aid if application is difficult - firmer compression is much easier to apply with the right tool.

This page is general education, not medical advice. If you have symptoms you have not discussed with a clinician, or you are unsure which compression level is right for you, speak with your doctor or a certified fitter before ordering.