What Compression Stockings Actually Do and Who Genuinely Needs Them

Veins in the legs work against gravity. Every time blood finishes its circuit through the lower limbs, it has to travel upward back to the heart, and the valves inside the veins are what keep it from pooling on the way. When those valves weaken or the vein walls lose their tone, blood collects in the lower leg, causing swelling, heaviness, and over time, the bulging cords of varicose veins.

Compression stockings apply graduated external pressure, tightest at the ankle and progressively lighter toward the knee or thigh. That pressure narrows the diameter of the superficial veins, which does two things: it pushes blood into the deeper venous system, where flow is stronger, and it reduces the diameter each valve has to close across, making an already-weakened valve more effective. The result is faster venous return and less pooling. The stocking is not treating anything. It is compensating for a mechanical problem while it is on.

The people for whom compression stockings are a clinical tool, not a wellness accessory, fall into a few clear groups.

People with chronic venous insufficiency, where the valves are persistently damaged, use compression as ongoing management. Without it, the pressure of pooled blood gradually damages the skin and soft tissue of the lower leg, eventually causing discolouration, thickening, and in severe cases, venous ulcers that are difficult to heal. The Indian Association of Vascular and Endovascular Surgeons includes graduated compression as a first-line recommendation in this condition.

People recovering from deep vein thrombosis wear compression to reduce the risk of post-thrombotic syndrome, a chronic swelling and pain that develops when the clot damages the vein wall. The timing and pressure class in this case come from the treating physician, not a pharmacy shelf.

People at elevated DVT risk during long-haul travel, particularly those with a prior clot, known clotting disorders, recent surgery, or active cancer, are the ones for whom flight socks have an evidence base. For a healthy person on a four-hour flight, the absolute risk of DVT is low enough that compression adds little. Walking the aisle and staying hydrated does roughly the same job.

People who stand for long shifts, nurses, surgeons, retail workers, often find compression reduces end-of-day swelling and fatigue. This is real, though it is comfort and prevention rather than treatment of a diagnosed condition.

Compression stockings are graded in millimetres of mercury, the same unit as blood pressure. The classes matter because the wrong pressure for the wrong person is not neutral.

Class 1 (15 to 20 mmHg) is what most pharmacy and travel stockings sit at. Adequate for mild swelling, tired legs, and low-risk travel. Class 2 (20 to 30 mmHg) is the standard clinical prescription for chronic venous insufficiency and post-DVT management. Class 3 (30 to 40 mmHg) and above are used in severe cases and are fitted by a specialist. Applying Class 3 pressure to legs with arterial disease, where blood supply to the limb is already reduced, can cause tissue damage. This is why a GP or vascular specialist checks ankle-brachial pressure index before prescribing high-class compression to anyone with diabetes, peripheral artery disease, or significant cardiovascular history.

Compression is not universally safe. Anyone with peripheral arterial disease should not use compression above Class 1 without medical clearance, because the external pressure compounds the existing shortfall in blood delivery to the limb. People with significant heart failure need medical guidance before use, since returning more blood volume to the central circulation can stress a heart that is already struggling. Diabetic neuropathy, which reduces sensation in the feet, means a poorly fitted stocking can cause pressure sores without the person noticing. A qualified professional should assess fit in this group. If you are in any of these categories, this is a conversation for your doctor before you buy anything.

Compression stockings do not reverse varicose veins. They do not repair damaged valves. They do not reduce the visible appearance of veins. They do not prevent varicose veins from developing in someone genetically predisposed, though they may slow progression in an already-affected leg. A stocking taken off at the end of the day returns the leg to exactly the state it would have been in without it, which is why, for clinical conditions, they are worn daily rather than occasionally. The people who wear them once before a flight and conclude they do nothing are usually right: for a healthy person with no risk factors, they often don't.