Compression stockings are a cornerstone of medical therapy for various circulatory conditions. Unlike regular socks, they apply measured, graduated pressure to the legs, with the intensity defined in millimeters of mercury (mmHg). This pressure rating is the single most critical factor determining their medical purpose.

The mmHg scale indicates the amount of pressure exerted at the ankle. Pressure gradually decreases up the leg, promoting blood flow back toward the heart. This gradient is key to their function. Stockings are categorized into different compression classes based on this ankle pressure.

For mild support and symptom relief from tired, aching legs or minor swelling, 15-20 mmHg (Class 1) is often recommended. This level is also common for travel and pregnancy.

The 20-30 mmHg (Class 2) range is the standard for treating moderate medical conditions. It is frequently prescribed for varicose veins during pregnancy, moderate edema, and for preventing the progression of venous insufficiency. It is also the typical grade used for post-sclerotherapy treatment and to help prevent deep vein thrombosis (DVT) in at-risk patients.

30-40 mmHg (Class 3) stockings are for severe conditions, such as severe varicose veins, post-thrombotic syndrome, significant edema (lymphedema), and for managing active venous ulcers.

The strongest grade, 40-50 mmHg (Class 4), is reserved for the most extreme cases of lymphatic and venous disorders, like severe chronic lymphedema, and requires precise medical supervision.

Selecting the correct mmHg is not a matter of personal preference. A healthcare professional must make the diagnosis and prescription. Using pressure that is too low may be ineffective, while pressure that is too high can be harmful. Proper measurement of the ankle and calf is essential for a correct fit, as an ill-fitting stocking cannot deliver the intended therapeutic pressure gradient.

In summary, compression stockings are a powerful medical tool. Their efficacy hinges entirely on the appropriate mmHg rating prescribed for a specific condition, ensuring safe and effective treatment to improve venous return, reduce swelling, and enhance overall vascular health. Always consult a doctor or certified fitter to determine the right compression level for your individual needs.