What is the difference between support stockings and compression stockings?
They are not the same garment. A support stocking has no defined pressure and no defined pressure gradient, is usually sold in shoe sizes or in ready-made small, medium and large, and is intended only for people with healthy veins who get heavy, tired legs from long sitting or standing. A medical compression garment applies a certified pressure that is strongest at the ankle and falls continuously up the leg. The manufacturer medi puts it plainly: support stockings "have no defined pressure distribution" and "are not a medical product because they do not have the properties of medical aids", while medical compression stockings carry a defined pressure distribution under the German RAL quality standard and are used to treat venous and lymphatic disease such as varicose veins and lymphoedema medi.
Most people searching for "support stockings" or "flight socks" are describing what a clinician calls graduated compression. What matters is not the word on the packet but whether your leg needs a garment with a known pressure. For a lot of people it does not, and we say exactly when below.
How does graduated compression actually work?
Blood returns from the foot to the heart against gravity, pushed by the calf muscle pump and held in place by one-way valves. Graduated compression supports that system mechanically: the garment squeezes hardest at the ankle and progressively less further up, so that, as medi describes it, "the veins between the muscles are compressed, and the venous valves close better" and "the blood does not collect in the legs, which also counteracts the formation of blood clots" medi.
That falling gradient is the whole point, and it is the part a shelf support stocking cannot promise. RAL certification requires a continuously decreasing pressure curve from the ankle upwards, and the ankle reading is what a garment is classified on, because that is where pressure is highest medi. A garment gripping harder at the calf than the ankle, or unevenly because it is the wrong shape for your leg, works against the mechanism. That is why our compression service treats class, length, knit and stiffness as four separate clinical decisions.
What do the compression classes and mmHg numbers mean?
Compression is measured in millimetres of mercury (mmHg) at the ankle, and the number or class on the packet tells you how hard the garment squeezes there. Three labelling systems are in circulation, which is where much of the confusion comes from: an unregulated support category with no number, a US retail scale written as an mmHg band, and the European RAL classes. The rows below give the verified ranges, from medi for the RAL classes medi, Sigvaris for the mmHg bands and their stated uses Sigvaris, and a peer-reviewed trial report for the British Standard PMC.
| What the label says | Standard it follows | Pressure at the ankle | What it is genuinely for | How it is sized |
|---|---|---|---|---|
| Support stocking, travel sock, flight sock, no class number | None, not a medical device | Not defined and not certified | Healthy veins, and heavy or tired legs after long sitting or standing | Shoe size, or ready-made small, medium and large |
| 15-20 mmHg | US retail scale | 15 to 20 mmHg | Day-to-day relief from achy, heavy, slightly swollen legs, and support in pregnancy | Off the shelf, by shoe and calf size |
| 20-30 mmHg | US retail scale | 20 to 30 mmHg | The level most commonly prescribed by doctors: varicose veins and mild oedema | Measured on the leg |
| 30-40 mmHg | US retail scale | 30 to 40 mmHg | Moderate and severe oedema and lymphoedema, serious varicose veins, venous stasis ulcers | Measured, often made-to-measure |
| Class 1 | European RAL | 18 to 21 mmHg | The lightest medical class for venous and lymphatic disease | Measured: series size or made-to-measure |
| Class 2 | European RAL | 23 to 32 mmHg | The standard working class for venous and lymphatic disease | Measured: series size or made-to-measure |
| Class 3 | European RAL | 34 to 46 mmHg | The heaviest class in routine use, commonly flat knit | Measured, usually made-to-measure |
| Class 1, 2 and 3 | British Standard | 14 to 17, 18 to 24 and 25 to 35 mmHg | The same class names as the European scale, at lower pressures | Measured |
Read the last two rows together, because this catches people out constantly. A British Standard class 2 delivers 18 to 24 mmHg at the ankle; a European class 2 delivers 23 to 32 mmHg. The literature notes that British and European standard stockings differ in the degree of compression exerted on the limb, and that the difference is a source of concern requiring awareness among clinicians PMC. So if a doctor writes "class 2" and you order online from another market, you may not get the pressure intended. A RAL class 4 above 49 mmHg exists but is not in routine use medi.
When is a pharmacy compression stocking genuinely the right buy?
Often, and we would rather say so than sell you an appointment you do not need. If your veins are healthy, your legs simply ache after a long shift on your feet or a long flight, and any swelling has gone by the next morning, an off-the-shelf pair is a reasonable purchase. Sigvaris lists 15 to 20 mmHg as the level offering "day-to-day relief from achy, heavy, slightly swollen legs" and support during pregnancy Sigvaris. You do not need a fitting to buy that.
Flight socks are the clearest example. A Cochrane review of 12 randomised trials involving 2,918 airline passengers found compression stockings cut symptomless deep vein thrombosis from a few tens per thousand passengers to two or three per thousand on high-certainty evidence, and that wearers had less leg swelling. No deaths, pulmonary emboli or symptomatic DVTs occurred in any trial, so the effect on those outcomes could not be assessed Cochrane. A meta-analysis of air travel studies notes the stockings used were knee-length class 1 and class 2, ankle pressures of 14 to 30 mmHg PMC, which overlaps the 15 to 20 mmHg band in the rows above.
This is the same logic we apply to braces on our off-the-shelf orthotics page: if the shelf product does the job, buy the shelf product. Just buy a graduated one, check the packet states an mmHg figure, and measure your ankle and calf rather than guessing from shoe size.
When is an off-the-shelf stocking the wrong call?
When the leg has a diagnosed problem rather than a tiredness problem. Compression becomes treatment rather than comfort in lymphoedema, in venous leg ulceration or a healed ulcer, in swelling still present when you wake, after a deep vein thrombosis or with post-thrombotic syndrome, and where the leg has changed shape with deep skin folds or swollen toes and forefoot. There, class, knit and fit all have to be chosen deliberately.
Knit construction is the part shoppers never see. Circular knit is seamless, smoother and stretchier, and serves as the basic therapy for venous disease. Flat knit is stiffer, with what medi calls wall stability, and is mainly used in treating lymphoedema and lipoedema; where leg circumferences differ markedly or the shape is irregular, flat knit is often necessary, and made-to-measure "will provide the best possible fit as it is tailor-made to the patient" medi. Sigvaris places moderate and severe oedema and lymphoedema, serious varicose veins and venous stasis ulcers at 30 to 40 mmHg Sigvaris, which is not a pressure to pick off a shelf.
Diabetes changes the calculation too, not because compression is automatically unsafe but because sensation may be reduced, so a garment that is cutting in may not feel like it is. The international consensus statement on compression risks lists severe diabetic neuropathy with sensory loss, and microangiopathy carrying a risk of skin necrosis, among conditions requiring caution, with special precautions in polyneuropathy and frail, atrophic skin consensus statement. If that describes your leg, our conditions page covers what we manage.
Why can you not buy compression by shoe size?
Because the class is defined at the ankle and the gradient depends on the circumferences of your particular leg, so the garment is knitted to those circumferences, not to your foot. Two people with the same shoe size can have very different ankle and calf measurements, and a garment delivering the right pressure on one will deliver the wrong pressure on the other. That is the split medi describes: support stockings come "only as round knit series products, i.e. in a few predefined sizes", while medical compression is "available in predefined series sizes or as individual made-to-measure products" medi.
We measure at each landmark the garment is knitted to, in the morning, before the leg has had the day to swell. That matches how it is meant to be worn: medi advises wearing medical compression from morning to evening and removing it at night, the exception being thrombosis prophylaxis in hospital, where stockings are worn continuously during bed rest medi.
Compression is also not a once-off purchase. Stockings worn and washed daily "maintain their effect for about six months", after which the compression effect of the material slowly falls medi. A two-year-old garment that still slides on easily has stopped working.
Why is screening for arterial disease part of a proper fitting?
Because compression squeezes the leg, and if the arteries supplying that leg are already narrowed, added external pressure can reduce the blood getting in. This is the one genuine safety risk in compression, and the reason a proper fitting starts with arterial screening rather than a tape measure. The international consensus statement on the risks and contraindications of medical compression lists severe peripheral arterial occlusive disease as an absolute contraindication to sustained compression, defined as an ankle-brachial pressure index below 0.6, ankle pressure below 60 mmHg, toe pressure below 30 mmHg, or transcutaneous oxygen pressure below 20 mmHg consensus statement.
It also lists severe cardiac insufficiency (NYHA class IV) as an absolute contraindication, advises against routine compression stockings in NYHA class III, and adds suspected compression of an existing epifascial arterial bypass and confirmed allergy to the material. None of that is detectable by a shop assistant or a size chart. Arterial supply, skin integrity and sensation are checked before anything is fitted through our compression service, and where screening raises a question the next step is referral to your GP or a vascular surgeon, not a lighter class as a compromise.
When should you see someone about compression?
Book an assessment if you have been prescribed a class and are unsure what to buy, if you have lymphoedema, a venous ulcer, swelling present in the morning or a history of DVT, if you have diabetes or known arterial disease and compression has been suggested, or if a garment you already wear hurts, rolls, cuts in or slides down. If your legs are simply tired at the end of a long day, buy the pharmacy pair and spend the money elsewhere.
Farida Cajee-Botes is an HPCSA-registered orthotist and prosthetist (registration OS 0015148), seeing patients by appointment at the Orthocast Morningside consulting rooms in Sandton, with home and hospital visits across Centurion, Pretoria, Midrand, Sandton and Johannesburg. Book an assessment and we will start with screening and measurement rather than with a product.
This article is general information and is not a substitute for individual clinical assessment. Compression is not safe for every leg, so if you have arterial disease, heart failure, diabetes with reduced sensation, or an unexplained swollen or painful leg, speak to your doctor before starting compression of any class.
Key takeaways
- A support stocking has no defined pressure and no defined pressure gradient and is not a medical device. A medical compression garment is certified to a pressure range measured at the ankle, falling continuously up the leg.
- The European RAL classes are 18 to 21 mmHg (class 1), 23 to 32 mmHg (class 2) and 34 to 46 mmHg (class 3). The British Standard uses the same class names at lower pressures (14 to 17, 18 to 24 and 25 to 35 mmHg), so "class 2" is not one thing.
- For healthy veins, tired legs and long flights, the pharmacy pair is genuinely the right buy. Cochrane found flight socks cut symptomless DVT in airline passengers, and the air-travel trials used knee-length class 1 and 2 stockings at 14 to 30 mmHg.
- Lymphoedema, venous ulceration, swelling that is still there in the morning, post-thrombotic syndrome and an irregular limb shape need a measured, often flat-knit garment, not a shelf product.
- Screening for arterial disease is part of a proper fitting. Severe peripheral arterial disease (ankle-brachial pressure index below 0.6, ankle pressure below 60 mmHg, toe pressure below 30 mmHg, or transcutaneous oxygen pressure below 20 mmHg) is an absolute contraindication to sustained compression.
Have a question about your own situation?
Every device we provide starts with an individual assessment: at home, in hospital, or at the practice.
References
- Support stockings are not medical compression stockings (medi)
- What are the compression classes for compression stockings? (medi)
- How do medical compression stockings work? Why wearing them makes sense (medi)
- How long should compression stockings be worn? At night too? (medi)
- Flat knit vs circular knit: what's the difference? (medi USA)
- Compression levels and when to wear which one (Sigvaris)
- Risks and contraindications of medical compression treatment: a critical reappraisal. An international consensus statement (Phlebology, via PMC (National Library of Medicine))
- Compression stockings for preventing deep vein thrombosis in airline passengers (Cochrane)
- Knee-length graduated compression stockings for thromboprophylaxis in air travellers: a meta-analysis (PMC (National Library of Medicine))
- Randomised controlled trial comparing European standard class 1 to class 2 compression stockings for ulcer recurrence and patient compliance (PMC (National Library of Medicine))