Leg Swelling (Lower Limb Oedema): Causes, When to Worry, and What to Do

December 27, 2021 | Dr Reza Moazzeni, Cardiologist |

Last Updated: May 27, 2026

Patient resource · Heartcare Sydney

Swollen legs and ankles are usually venous, cardiac, drug-related or lymphatic. The first question to ask in leg swelling is whether one leg is swollen or both — that single observation narrows the causes of lower limb oedema more than any test.

Urgent — do not delay

Seek urgent medical assessment if you have:

Sudden swelling of one leg with calf pain, warmth or tenderness (possible deep vein thrombosis)
One leg that is red, hot and painful, with fever or feeling unwell (possible cellulitis)
Swelling in both legs with severe breathlessness, especially when lying flat
Chest pain, fainting, or coughing up blood with new leg swelling (possible pulmonary embolism)

For any of these, go to your nearest emergency department or call 000.

The diagnostic question: one leg or both?

The single most useful question in leg swelling is whether one leg is affected or both. The causes often differ, and the urgency can differ sharply.

One leg swollen — the cause is almost always local: a blood clot, an infection, a damaged vein system, blocked lymphatic drainage, or an injury.
Both legs swollen — the cause is usually systemic: the heart, the kidneys, the liver, a medication, or a problem affecting both venous or lymphatic systems together.

There is some overlap. Asymmetric chronic venous insufficiency, bilateral DVT, and pelvic or iliac vein obstruction can blur the boundary, and systemic causes sometimes appear worse on one side. The laterality question still narrows the differential more than any other single observation.

A new swelling that appeared over hours to days is treated very differently from a swelling that has built up over weeks to years. Combining laterality (one leg or both) with time course (sudden or gradual) covers most of the diagnostic work in the first few minutes of a consultation.

Diagnostic decision tree for leg swelling. Laterality (one leg or both) is the first question; acuity or pitting status narrows the differential further. Listed causes are illustrative, not exhaustive.

When one leg is swollen

Unilateral swelling is less common than bilateral and more concerning, because the causes include conditions that need treatment within hours.

Most common causes of one swollen leg

Deep vein thrombosis (DVT)

A blood clot in a deep leg vein. Often a tight, aching calf with warmth and tenderness. Risk rises with recent surgery, long-haul travel, immobility, cancer, oestrogen-containing contraception or HRT, and previous DVT. Diagnosed by duplex ultrasound; treated with anticoagulants.

Cellulitis

A bacterial skin infection. The leg becomes red, warm and tender, often with fever and feeling unwell. The border may be diffuse rather than sharp. Treated with antibiotics; severe cases need hospital admission.

Chronic venous insufficiency (CVI)

When valves in the leg veins fail and blood pools downward. Sometimes one leg is worse than the other. Skin changes, varicose veins, and end-of-day heaviness are typical. See the dedicated guide on chronic venous insufficiency (coming soon).

Post-thrombotic syndrome (PTS)

A common long-term consequence of a previous DVT, affecting roughly one in five to one in two people depending on severity and definition. Chronic swelling, skin discolouration and sometimes ulcers in the affected leg.

Lymphoedema

When the lymphatic system cannot drain fluid properly. Often follows cancer treatment (surgery, radiation) or chronic infection. The swelling can be one-sided when the cause is one-sided. See the dedicated lymphoedema guide (coming soon).

Less common

Ruptured Baker's cyst (fluid behind the knee tracking down the calf), pelvic vein compression (a mass or anatomical issue blocking venous return), and significant injury or trauma.

Post-thrombotic syndrome showing chronic hyperpigmentation, skin thickening and lipodermatosclerosis of the left leg from a previous deep vein thrombosis — **Post-thrombotic syndrome** Chronic skin changes and persistent unilateral swelling years after a deep vein thrombosis.

Traumatic lymphoedema showing marked unilateral swelling of the right leg from a previous injury and lymphatic damage — **Traumatic lymphoedema** Marked unilateral swelling from lymphatic damage after an old injury.

Acute causes: DVT, cellulitis, or ruptured Baker's cyst?

These three conditions present similarly — one swollen, painful leg appearing over hours to a day or two — but the differences matter. Distinguishing them shapes whether the priority is anticoagulation, antibiotics, or imaging.

Feature	DVT	Cellulitis	Ruptured Baker's cyst
Onset	Hours to days	Hours to a day	Sudden, often with sharp pain
Skin	May be mildly red, often pale	Red, warm, often spreading; border may be indistinct	Bruising tracking down calf
Temperature	Warm	Hot	Variable
Fever	Usually no	Often yes	No
Pain	Aching, calf tender	Tender, throbbing	Sudden pain behind knee
Test	Duplex ultrasound	Clinical, sometimes bloods	Ultrasound

For clinicians: a deeper clinical differential with case studies is available at Unilateral Leg Swelling: Differential Diagnosis and Case Studies.

When both legs are swollen

Bilateral swelling is more common than unilateral and usually points to a systemic cause — something affecting the whole body, not just the leg.

The next bedside question is whether the swelling pits.

Pitting versus non-pitting — what it tells you

Press a finger firmly into the skin over the shin bone for about five seconds. If a dent remains for a few seconds after you release, the swelling is pitting. If the indent springs back immediately, it is non-pitting.

This simple test divides bilateral leg oedema into two very different lists, though the boundary is not absolute. Early lymphoedema can still pit; later lymphoedema often becomes firmer and less pitting as fibrosis develops.

Type	What it suggests	Examples
Pitting	Excess fluid in the tissues	Heart failure, kidney disease, liver disease, medications, pregnancy, idiopathic / dependent, bilateral CVI
Non-pitting	Fat, protein-rich lymph fluid, or both	Lymphoedema, lipoedema, severe hypothyroidism (myxoedema)

Why this matters:

Pitting oedema is fluid. It generally responds to addressing the underlying cause — treating heart failure, changing a medication, treating kidney or liver disease.
Non-pitting swelling is tissue change — fat in lipoedema, protein-rich fluid and fibrosis in lymphoedema. It does not respond to diuretics, and the treatment is fundamentally different.

Bilateral pitting causes — the systemic group

The most common bilateral pitting causes are systemic. Heart failure is the one a cardiologist is most often asked to assess — it is treated separately below. The other systemic causes are summarised in the table that follows.

Heart failure

The cardiology cause

When the heart cannot pump or fill efficiently, neurohormonal systems activate — the renin-angiotensin-aldosterone system and the sympathetic nervous system both tell the kidneys to retain sodium and water. Pressure builds up behind the right side of the heart and fluid leaks into the legs.

Pattern: Bilateral, pitting, worse at end of day. Often accompanied by breathlessness on exertion, breathlessness lying flat (orthopnoea), or waking at night gasping for air (paroxysmal nocturnal dyspnoea).
Investigation: A blood test called BNP or NT-proBNP, plus an echocardiogram. The echo distinguishes HFrEF (reduced ejection fraction) from HFpEF (where the heart pumps normally but does not relax properly).
Why it matters: Heart failure is treatable. Early diagnosis changes life expectancy, not just symptoms. New bilateral leg swelling with any breathlessness deserves a cardiology assessment.

Concerned about heart-related leg swelling?

Book an assessment

Other bilateral pitting causes

Cause	Tell-tale clue	Investigation / next step
Kidney disease	Frothy urine, puffiness around the eyes, known CKD. Severe kidney disease causes oedema by retaining sodium and water, and by losing protein in the urine.	Urine albumin-to-creatinine ratio, kidney function tests — GP review
Liver disease	Abdominal swelling (ascites), known liver disease, low blood albumin. Advanced liver disease lowers albumin and raises portal venous pressure.	Liver function tests, abdominal examination — GP review
Medication-induced	New medication started in the last weeks to months. Calcium channel blockers (especially amlodipine) are the most common.	Medication review — see the drug section below
Bilateral CVI	Worse at end of day, varicose veins, brown ankle skin changes. Both leg vein systems can be incompetent, particularly in older patients or those with standing occupations.	Venous duplex ultrasound
Idiopathic, dependent or orthostatic oedema	Resolves overnight, otherwise well, often worse in warm weather or after long periods of standing or sitting.	Reassurance, elevation, compression if persistent
Pregnancy	Late pregnancy, mild and symmetrical. Sudden severe oedema with high blood pressure or visual changes can suggest pre-eclampsia.	Routine obstetric review; urgent assessment if BP elevated or symptoms suggest pre-eclampsia
Obstructive sleep apnoea	Snoring, daytime sleepiness, weight gain. OSA can contribute through several mechanisms including raised right-heart pressures and overnight fluid shifts.	Sleep study consideration — GP review

Bilateral non-pitting causes — the tissue group

Non-pitting swelling is tissue change rather than fluid — the treatment approach is fundamentally different from the pitting causes above.

Cause	Tell-tale clue	Investigation / next step
Lymphoedema	Positive Stemmer sign (cannot pinch a fold of skin at the base of the second toe), includes the dorsum of the foot, often follows cancer treatment or chronic infection. Early lymphoedema may still pit; later lymphoedema becomes firmer and fibrotic.	Largely clinical diagnosis — lymphoedema therapist referral; dedicated lymphoedema guide coming soon
Lipoedema	Almost exclusively in women. Symmetrical, painful fat deposition in the legs (and sometimes arms) that spares the feet, with a distinctive band-like fold at the ankle.	Clinical diagnosis — see our lipoedema guide
Myxoedema	Severe hypothyroidism. Tired, cold-intolerant, weight gain, puffy face and hands as well as shins.	Thyroid function tests (TSH, free T4) — GP review

Chronic venous insufficiency — a brief overview

Chronic venous insufficiency is one of the most common chronic causes of leg swelling. The valves inside the leg veins normally stop blood from flowing backwards; when they fail, blood pools in the lower leg under gravity. This raises pressure in the small vessels and leaks fluid into the tissues.

Typical features:

Heaviness and aching, worse at end of day, better with elevation
Visible varicose veins
Skin changes over time — brown discolouration, hardening of the skin around the ankle (lipodermatosclerosis), eczema, and in advanced cases venous ulcers

Lipodermatosclerosis showing skin hardening, woody texture and brown hyperpigmentation around the ankle in chronic venous insufficiency — Lipodermatosclerosis: skin hardening and brown hyperpigmentation around the ankle — a hallmark of chronic venous insufficiency.

The diagnostic test is a venous duplex ultrasound — a specific scan that looks for reflux (backward flow) in the leg veins.

For the full guide — staging, treatment options, when to consider procedures — a dedicated post on chronic venous insufficiency will be added as part of this cluster.

Dr Moazzeni discusses venous hypertension as a leading cause of lower limb oedema, with illustrative case examples.

Medications that cause leg swelling

Drug-induced oedema is common, often missed, and easily reversed once recognised. A medication change frequently resolves the problem without further investigation.

Drug class	Examples	Mechanism	Time course
Calcium channel blockers (dihydropyridines)	Amlodipine, felodipine, nifedipine	Arteriolar dilatation raises capillary pressure	Weeks to months
Other vasodilators · alpha-blockers	Prazosin, doxazosin, hydralazine, minoxidil	Arteriolar dilatation, similar mechanism to dihydropyridine CCBs	Weeks
Gabapentinoids	Gabapentin, pregabalin	Mechanism unclear; possibly endothelial	Days to weeks
NSAIDs	Ibuprofen, diclofenac, naproxen, celecoxib	Reduced kidney prostaglandins → sodium retention	Days to weeks
Thiazolidinediones	Pioglitazone	Increased sodium reabsorption; can precipitate heart failure	Weeks
Corticosteroids	Prednisone, prednisolone	Mineralocorticoid effect → sodium retention	Days to weeks
Oestrogens	Combined oral contraceptive, HRT	RAAS activation → sodium retention	Weeks

If you have developed leg oedema after starting a new medication, do not stop it on your own — speak with your GP, who can review whether the drug is contributing and consider an alternative.

A note on amlodipine specifically: Amlodipine oedema is dose-related and not relieved by diuretics. Switching to a different blood pressure class, or combining with an ACE inhibitor or ARB (which can offset the mechanism), is usually more effective.

When to see your GP, and when to see a cardiologist

Situation	Where to start
Stable bilateral swelling, no red flags, no breathlessness	Your GP
New medication started recently and now swollen	Your GP — for medication review
Possible varicose veins, skin changes around the ankle	Your GP first, then vascular referral
Bilateral pitting oedema with breathlessness or known heart disease	Cardiologist (echo, BNP, work-up)
Raised JVP, orthopnoea, paroxysmal nocturnal dyspnoea	Cardiologist
Suspected DVT, cellulitis, pulmonary embolism, or acute heart failure	Emergency department

If you are in Sydney and need a cardiology opinion, you can find more about our Westmead practice or book an appointment online. A GP referral is required for Medicare-rebated consultations.

Frequently asked questions

Why are my ankles swollen at the end of the day?

End-of-day ankle swelling that disappears overnight is usually dependent or orthostatic oedema — fluid pooling under gravity during the day, particularly after long periods of standing or sitting, or in warm weather. It is generally not serious if it is symmetrical, fully resolves overnight, and is not accompanied by breathlessness or other symptoms. Persistent or progressive swelling deserves a GP review.

How do I know if leg swelling is from my heart?

Heart-related leg swelling is almost always bilateral and pitting, and usually comes with other signs: breathlessness on exertion, difficulty lying flat, waking at night short of breath, or known heart disease. A simple blood test (BNP or NT-proBNP) and an echocardiogram are the main investigations.

Can blood pressure tablets cause swollen legs?

Yes — particularly the dihydropyridine calcium channel blockers (amlodipine is the most common). The swelling is dose-related and is caused by widening of small arteries, which raises pressure in the capillaries. Diuretics do not fix it well; switching class or adding an ACE inhibitor or ARB usually does. Speak with your GP or cardiologist before changing any medication.

Is one swollen leg always a blood clot?

No, but a new swelling in one leg should always be assessed promptly to exclude DVT, especially if there is calf pain, warmth, or recent immobility, surgery or travel. A duplex ultrasound rules it in or out.

Why do my legs swell only in summer?

Heat causes blood vessels to dilate and lowers the efficiency of venous return, which often unmasks mild dependent or venous oedema. If swelling appears in summer in an otherwise well person and resolves overnight, it is usually benign. Compression stockings, elevation and avoiding long periods of standing in the heat usually help.

Are compression stockings safe if I have heart failure?

For most patients with stable, well-controlled heart failure, graduated compression is safe and helpful. In severe or decompensated heart failure, compression can shift fluid centrally and worsen breathlessness — discuss with your cardiologist before starting. Compression should also be avoided or used cautiously in significant peripheral arterial disease (PAD). If you have reduced foot pulses, diabetes, a smoking history, or known PAD, your doctor may check an ankle-brachial index (ABI) before recommending compression.

Does drinking less water help leg swelling?

Generally no. Restricting fluid does not address the underlying cause and can worsen kidney function and cause other problems. For heart failure, fluid and salt restriction may be advised by your cardiologist, but this is individualised. For most other causes of leg swelling, normal fluid intake is appropriate.

When should I worry about leg swelling?

Any of the following warrants prompt medical assessment: sudden swelling of one leg, especially with pain or warmth; redness, heat and fever in a swollen leg; bilateral swelling with breathlessness, particularly at rest or lying flat; swelling that worsens rapidly over days; skin breakdown, ulceration, or weeping fluid; chest pain, palpitations or fainting with leg swelling.

References & further reading

Clinical references

De Maeseneer MG, et al. Editor's Choice — European Society for Vascular Surgery (ESVS) 2022 Clinical Practice Guidelines on the Management of Chronic Venous Disease of the Lower Limbs. Eur J Vasc Endovasc Surg. 2022;63(2):184-267.
Executive Committee of the International Society of Lymphology. The diagnosis and treatment of peripheral lymphedema: 2020 consensus document of the International Society of Lymphology. Lymphology. 2020;53(1):3-19.
Heidenreich PA, et al. 2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure. J Am Coll Cardiol. 2022;79(17):e263-e421.
Trayes KP, Studdiford JS, Pickle S, Tully AS. Edema: diagnosis and management. Am Fam Physician. 2013;88(2):102-110.
Therapeutic Guidelines (Australia, eTG complete) — entries on Chronic venous insufficiency, Cellulitis, Deep venous thrombosis.