After getting to grips with the various sizes, heights, colours and styles of compression garments out there, there’s still the crucial matter of compression ratings to deal with. After all, it is the compression action of these socks and stockings that separates them from normal, everyday garments.
Socks and stockings for compression therapy generally come in four or sometimes five compression levels, which indicates exactly how much pressure will be applied to the leg.
Strength of Compression
Compression clothing uses millimetres of Mercury (mmHg) when it comes to measuring the levels of compression (pressure). 1mm of mercury = 1/760 of an atmosphere of pressure. In science, the pressure is measured in Pascals (1 mmHg = 133.322367415 pascals); however, in medicine the standardised unit of compression level is measured in mmHg.
Compression Classes
While mmHg is a standardised unit of measure for the strength of compression, when it comes to classes of compression, there is no universal classification. There are two most common classifications (AFNOR and RAL) as well as the BSI classification.
The AFNOR standard comes from a French body for standardisation and normalisation (Association Française de Normalisation) and has the following break down of classes:
- Class 1: 10-15 mmHg (Very light compression)
- Class 2: 15-20 mmHg (Light compression)
- Class 3: 20-36 mmHg (Moderate compression)
- Class 4: 36+ mmHg (Strong compression)
The RAL standard comes from a German body and is generally used EU-wide:
- Class 1: 18-21 mmHg (Light compression)
- Class 2: 23-32 mmHg (Moderate compression)
- Class 3: 34-46 mmHg (Strong compression)
- Class 4: 47+ mmHg (Very strong compression)
The BSI standard comes from the British Standards Institute:
- Level 1: 14 - 17 mmHg (Light Compression for Active Use)
- Level 2: 18 - 24 mmHg (Moderate Compression for Active Use)
- Level 3: 25 - 35 mmHg (High Compression for Active Use & Recovery)
The following table contains most of the important information you’ll need to know, with regard to compression ratings and their respective uses:
| 8-15 mmHg (Mild Support) | 15-20 mmHg (Medium Support) | 20-30 mmHg (Firm Compression) | 30-40 mmHg (Extra Firm Compression) |
| Used for the gentle relief/prevention of achy and tired legs. | Used to treat and prevent spider veins and varicose veins of moderate severity. | Prescribed for the treatment of more advanced varicose and spider veins (sometimes during pregnancy). | Effective in the treatment of the most severe varicose veins and spider veins. |
| Effective when used during long periods of standing or sitting. | Good for treating tiredness, aches and minor swelling in the legs, ankles and feet. | Effective in the treatment of edema or lymphatic edema at a moderate to severe level. | Prescribed for the treatment of more severe cases of edema or lymphatic edema. |
| Can help prevent and relieve leg, ankle and feet-swelling of a minor nature. | Known to help prevent DVT (Deep Vein Thrombosis) while flying long distances. | Offers relief from superficial thrombophlebitis and can be useful in managing ulcers. | Used post-sclerotherapy treatment and post-surgery to prevent spider/varicose veins from reappearing. |
| Can help prevent spider veins and varicose veins forming during pregnancy. | Can help prevent spider veins and varicose veins forming during pregnancy. | Used as a preventative treatment against dangerous blood pressure crashes when standing up (hypotension) | Can be used to manage venous ulcers and post-thrombotic syndrome manifestations. |
| Good for keeping legs energized and healthy. | Used to help prevent spider veins and varicose veins following sclerotherapy treatment. | Used to help prevent spider veins and varicose veins following sclerotherapy treatment. |
Also effective in the prevention of deep vein thrombosis (DVT) in multiple settings. |
Over-the-Counter or Prescription Compression Socks?
Generally speaking, the lightest level of compression (under 15 mmHg) is recommended for individuals who are mostly in a good state of health, though are looking to relieve the discomfort of leg-fatigue attributed to standing all day, sitting all day or as a common consequence of pregnancy.
For airline pilots, flight attendants and passengers taking longer journeys, compression at a more moderate level (15 to 20 mmHg) is considered appropriate as an additional preventative measure against DVT.
Any compression levels higher than 20mmHg are generally referred to as medical-grade compression garments. The biggest difference in this instance being that they are almost always only available by way of prescription. These are the compression socks that are generally prescribed for the treatment of varicose veins, the prevention of blood clots following surgical procedures and for the treatment of edema. Medical-grade compression stockings usually fit more loosely at the top and tighter at the bottom, in order to ensure that the advanced pressure they place on the limb does not result in its circulation being dangerously restricted.
Buying Online
While medical-grade compression socks are generally only available on prescription, this doesn’t mean it isn’t relatively easy to buy them online with no prescription required. However, doctors and medical professionals in general comprehensively advise against doing so, given the way in which it is difficult to assess in advance the quality or safety of the products you are buying.
If you are a suitable candidate for medical-grade pressure socks that are necessary and important for your health and wellbeing, your doctor will recommend and prescribe them. If they refuse to do so, this is because you are not a suitable candidate and therefore should not be using medical-grade compression garments. Should you go ahead and do so, you could be putting your health or even your life at risk.
