Compression Garments: How to Choose the Right Level

How Graduated Compression Works

Medical compression garments are built to apply their highest pressure at the ankle, then gradually ease up the leg. That gradient is the entire point: it mechanically assists blood moving upward toward the heart instead of pooling or refluxing back down into the foot, and it supports the lymphatic vessels that drain excess fluid from the tissue. ^[1] The result, for many people, is less venous hypertension, less fluid buildup, and less end-of-day heaviness, which is why compression comes up so often alongside other everyday causes of fluid retention and swelling.

The evidence behind this is strongest for chronic venous insufficiency, where compression is a well-supported first-line, non-surgical treatment, including for healing venous ulcers. ^[1] It's more mixed for preventing deep vein thrombosis in some settings, and the benefit for otherwise-uncomplicated varicose veins is more modest than marketing sometimes implies. ^[1] In other words, graduated compression is a real, mechanism-backed tool, just not an equally powerful one for every use case. For how compression stacks up against dry brushing, massage and a daily supplement, see our Lymph Tonic vs dry brushing, massage and compression comparison.

The mmHg Compression Class System

Compression strength is measured in millimeters of mercury (mmHg), the same unit used for blood pressure, and garments are grouped into classes by how much pressure they apply at the ankle. ^[2] Roughly:

• Mild (8-15 or 15-20 mmHg). Sold over the counter for everyday tired or achy legs, minor swelling, long flights, or standing shifts at work. No prescription needed. ^[3]
• Moderate (20-30 mmHg). Often the first level a clinician recommends for varicose veins, mild-to-moderate edema, DVT prevention in higher-risk situations, or pregnancy-related swelling. Available over the counter in most places, though it's frequently used under medical guidance. ^[3]
• Firm (30-40 mmHg). Considered medical-grade and typically requires a prescription. Used for more significant chronic venous insufficiency, healing venous ulcers, post-sclerotherapy recovery, and as ongoing maintenance for lymphedema. ^[2]
• Extra-firm (40-50+ mmHg). Reserved for severe venous disease, post-thrombotic syndrome, and more advanced lymphedema, almost always prescribed and fitted by a specialist. ^[2]

Higher isn't automatically better. A class that's stronger than what a person's condition and skin can tolerate can be uncomfortable enough that it simply doesn't get worn; one review pointed to non-adherence rates as high as 30-65% for graduated compression stockings, mostly tied to difficulty putting them on and discomfort from a mismatched fit or class. ^[1]

Getting Properly Measured and Fitted

Compression only works the way it's designed to if the pressure gradient is intact along the whole limb, and that depends on getting sized correctly. Legs should be measured first thing in the morning, before the day's normal swelling has set in, at specific points: the ankle at its narrowest, the calf at its widest, and, for thigh-high or custom garments, additional points further up the leg. ^[4] For knee-high styles, the heel of the garment should sit at your actual heel and the top should land about two finger-widths below the back of the knee; thigh-high styles follow the same logic up to just below the gluteal fold. ^[4]

Fit isn't a minor detail here. In one controlled study on lymphedema, a properly adjusted compression stocking produced a meaningful reduction in limb volume, while a poorly adjusted one on the same type of patient showed essentially no benefit at all. ^[5] A garment that's too loose loses its gradient and does little; one that's too tight, especially at the top, can act like a tourniquet and restrict circulation instead of assisting it. Off-the-shelf sizing also doesn't conform evenly to every limb shape, which is part of why custom-measured, made-to-order garments exist for lymphedema and more complex venous cases, usually fitted by a trained therapist or manufacturer representative. ^{[6] [7]}

When to Involve a Doctor or Certified Fitter

Not every use case calls for the same level of oversight. Someone reaching for mild compression before a long flight or a day of standing generally doesn't need a prescription or a formal fitting. The calculus changes for anything more clinical:

• Post-surgical recovery. After vascular procedures, sclerotherapy, or lymph node surgery, compression class and fit are usually specified by the surgical team as part of recovery.
• Lymphedema. This typically calls for a certified lymphedema therapist, custom or made-to-measure garments, and ongoing reassessment as limb volume changes, which we cover in more depth in our guide to lymphedema causes and treatment.
• Diagnosed venous disease. Chronic venous insufficiency, healing ulcers, or a history of DVT usually warrant a specific prescribed class rather than an over-the-counter guess.
• Everyday leg fatigue or travel. Mild-to-moderate, well-fitted, off-the-shelf compression is generally considered low-risk for this use case. ^[3]

Formal consensus guidance treats significantly reduced arterial flow, measured through tests like the ankle-brachial index, as a genuine contraindication rather than a minor caution, and recommends dialing compression down or avoiding it altogether once arterial supply is compromised. ^[8] If a garment ever causes numbness, worsening pain, cold or discolored toes, or skin breakdown, that's a signal to stop and get it reassessed rather than push through it.