Oedema: prevention, diagnosis and when to see a doctor
Swollen ankles after a long flight are rarely a worry, but swelling can also be the first sign of a blood clot, heart failure or a medicine side effect. Our editorial team explains how to tell the difference and when to get help.
What oedema is
Oedema is the medical term for swelling caused by excess fluid in the body's tissues. It most often appears in the feet, ankles and lower legs, where gravity encourages fluid to collect, but it can also affect the hands, face, abdomen or, in serious cases, the lungs.
Fluid constantly moves between blood vessels and tissues. The balance depends on pressure inside the vessels, the amount of protein in the blood (mainly albumin, which holds water in), the permeability of vessel walls and the lymphatic system, which drains fluid away. Oedema develops when one or more of these is disturbed.
A simple bedside sign is "pitting": pressing a thumb firmly into a swollen area for several seconds and seeing whether a dent remains. Pitting oedema suggests free fluid, while non-pitting swelling can point to lymphatic problems or thyroid disease.
A review by Trayes and colleagues in American Family Physician sets out a practical approach: determine whether swelling is in one limb or both, whether it came on suddenly or gradually, and whether there are signs of an underlying disease of the heart, kidneys, liver or veins.
Common causes, including in active people
Many causes of swelling are harmless and temporary. Standing or sitting for long periods, hot weather, long-haul flights, a salty meal and the premenstrual phase of the cycle can all produce mild, symmetrical ankle swelling that resolves overnight.
| Category | Examples | Typical pattern |
|---|---|---|
| Everyday and benign | Heat, prolonged standing, flights, high salt, menstrual cycle | Both legs, mild, better with rest |
| Medicines | Some blood pressure drugs, NSAIDs, steroids, hormones | Both legs, starts after a new drug |
| Vein problems | Chronic venous insufficiency, varicose veins | Worse by evening, skin changes |
| Blood clot | Deep vein thrombosis | One leg, sudden, painful, warm |
| Organ disease | Heart failure, kidney or liver disease | Both legs, often with other symptoms |
| Injury | Sprains, muscle tears, fractures | Localised, linked to trauma |
Medicines are an often overlooked cause. Calcium-channel blockers such as amlodipine commonly cause ankle swelling, as Sica has reviewed. Anti-inflammatory painkillers, used widely by athletes, encourage the kidneys to retain salt and water.
In gym culture, anabolic steroids and other hormones frequently cause fluid retention, partly through effects on sodium handling and oestrogen. Insulin misuse can also cause oedema, but the far greater danger is severe hypoglycaemia, which can be fatal. Creatine increases water inside muscle cells; this is not the same as oedema and does not cause pitting swelling.
When swelling is an emergency
Most swelling can wait for a routine appointment, but some patterns need urgent help. Recognising them is the single most important message of this article.
- Call 999 if swelling of the face, lips, tongue or throat comes on suddenly, especially with difficulty breathing or swallowing; this may be anaphylaxis or angioedema.
- Call 999 if leg swelling is accompanied by chest pain, sudden breathlessness or coughing up blood, which can indicate a pulmonary embolism.
- Seek same-day care (NHS 111 or urgent GP) for one swollen, painful, warm or red calf, which may be a deep vein thrombosis.
- Seek same-day care for swelling with breathlessness when lying flat or waking breathless at night, suggestive of heart failure.
- Seek prompt advice for swelling in pregnancy with headache, visual disturbance or upper abdominal pain, which may signal pre-eclampsia.
NICE guidance on venous thromboembolism (NG158) describes how clinicians assess suspected clots using clinical scoring, D-dimer blood tests and ultrasound. Athletes are not immune: long-haul travel to competitions, leg injuries, immobilisation in a cast and dehydration all raise the risk.
Endurance athletes should also know about exercise-associated hyponatraemia, in which overdrinking causes low blood sodium. Swollen hands and feet, headache and confusion after a long race are warning signs that require urgent assessment.
How doctors investigate oedema
Diagnosis starts with history and examination. The clinician will ask when swelling began, whether it affects one or both sides, what makes it better or worse, and what medicines, supplements and substances you use. Ely and colleagues proposed a structured approach to unexplained leg swelling that remains widely referenced.
Blood tests commonly include kidney function, liver function and albumin, thyroid function and a full blood count. A urine test checks for protein, which can indicate kidney disease. If heart failure is suspected, a blood test for natriuretic peptide (NT-proBNP) helps decide whether an echocardiogram is needed, in line with NICE guidance on chronic heart failure (NG106).
Imaging depends on the suspected cause. Doppler ultrasound is used for clots and vein problems; echocardiography for the heart; and, more rarely, lymphatic imaging when lymphoedema is suspected.
For athletes, mentioning recent training load, travel, injuries, dietary changes and any performance-enhancing substances is vital. Clinicians need the full picture to reach the right answer.
Prevention and self-care
For mild, benign swelling, simple measures often help. Move regularly during long periods of sitting or standing, flex the calves on flights, and raise the legs above heart level when resting.
Reducing salt intake can make a noticeable difference. The NHS recommends that adults eat no more than 6 g of salt a day, and much of it comes from processed foods rather than the salt shaker. Athletes who use high-sodium electrolyte products should factor them into their total.
Compression stockings can help venous swelling, but they are not suitable for everyone, particularly people with poor arterial circulation. Ask a pharmacist or GP before using them for anything more than short-term travel.
Do not take diuretics ("water pills") without a prescription to reduce swelling or to look leaner. Misused diuretics can cause dangerous dehydration and electrolyte disturbances, including heart rhythm problems, and they are prohibited in sport.
Editorial conclusions
Oedema is a sign, not a diagnosis. Mild, symmetrical swelling after heat, travel or long days on your feet is common and usually harmless.
Swelling in one leg, swelling with breathlessness or chest pain, and sudden facial swelling require urgent medical attention.
Medicines, including painkillers and blood pressure tablets, and performance-enhancing substances are frequent and often overlooked causes.
For further reading, see our articles on deep vein thrombosis in athletes, NT-proBNP testing and the risks of diuretic misuse.
References
- Trayes KP, Studdiford JS, Pickle S, Tully AS. Edema: diagnosis and management. Am Fam Physician. 2013;88(2):102–110.
- Ely JW, Osheroff JA, Chambliss ML, Ebell MH. Approach to leg edema of unclear etiology. J Am Board Fam Med. 2006;19(2):148–160.
- Sica DA. Calcium channel blocker-related peripheral edema: can it be resolved? J Clin Hypertens. 2003;5(4):291–294.
- National Institute for Health and Care Excellence. Venous thromboembolic diseases: diagnosis, management and thrombophilia testing. NICE guideline NG158. London: NICE; 2020.
- National Institute for Health and Care Excellence. Chronic heart failure in adults: diagnosis and management. NICE guideline NG106. London: NICE; 2018.
- Pope HG Jr, Wood RI, Rogol A, et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev. 2014;35(3):341–375.
