Symptom Guide

Swollen Feet & Ankles

Name: Swollen Feet & Ankles: Causes & Blood Tests | HealthReview
Creator: Suman Konda
Published: 2026-07-05

Swelling (oedema) in the feet and ankles can range from harmless to a sign of heart, kidney or liver disease. The right blood tests can identify the cause quickly.¹

Written by Suman Konda, PharmD, Clinical Pharmacist · Editorial policy · Not medical advice

Last updated: 01 August 2026 · How we check our content

Blood tests ordered for swollen feet

Test	Normal Range	Why it's done
Albumin	3.5–5.0 g/dL	Low albumin = fluid leaks into tissues (oedema)
Creatinine / eGFR	eGFR >60 mL/min	Kidney disease causing fluid retention
BNP / NT-proBNP	BNP <100 pg/mL	Heart failure marker: swelling from poor heart pump
TSH	0.4–4.0 mIU/L	Hypothyroidism causes non-pitting oedema (myxoedema)
LFT (Albumin, Bilirubin)	Albumin >3.5 g/dL	Liver cirrhosis causing protein loss and fluid retention
CBC	Hb Men >13.5 g/dL	Anaemia: can cause leg oedema
Urine protein	Negative	Nephrotic syndrome: kidneys losing protein
D-Dimer	<0.5 mg/L	DVT (deep vein thrombosis): clot causing one-sided swelling

What causes swollen feet and ankles?

Heart failure

When the heart is not pumping effectively, blood backs up in the veins, causing fluid to leak into the surrounding tissues. This causes bilateral (both legs) pitting oedema: swelling that leaves a dent when pressed. Swelling is worse in the evening and after standing. BNP or NT-proBNP is the key blood test, elevated levels indicate the heart is under strain. A chest X-ray and echocardiogram (heart ultrasound) are usually arranged.

Kidney disease / Nephrotic syndrome

Kidneys damaged by diabetes, hypertension or glomerulonephritis may lose protein into the urine (proteinuria). Low blood protein (low albumin) means less oncotic pressure to hold fluid in blood vessels: fluid leaks into tissues. Swelling is often first noticed around the eyes in the morning. Urine protein and albumin are the key tests. eGFR tells you how much kidney function is left.

Liver disease / Cirrhosis

The liver makes albumin. When the liver is severely damaged (cirrhosis), albumin production falls, causing protein-losing oedema. Liver cirrhosis also raises pressure in the portal vein (portal hypertension), causing fluid to accumulate in the abdomen (ascites) and legs. LFT will show low albumin, raised bilirubin, and raised INR.

Hypothyroidism (underactive thyroid)

Low thyroid hormone causes a unique type of swelling called myxoedema: a non-pitting oedema caused by mucopolysaccharide deposits under the skin. Unlike pitting oedema, pressing the skin does not leave a dent. TSH will be elevated. This resolves with thyroid hormone replacement (levothyroxine).

Deep Vein Thrombosis (DVT)

A blood clot in the deep veins, usually the calf or thigh: causes one-sided swelling, pain, warmth and redness. DVT is a medical emergency because clots can break off and travel to the lungs (pulmonary embolism). D-Dimer is the initial blood test, if elevated, a Doppler ultrasound of the leg veins confirms the diagnosis.

Venous insufficiency and other benign causes

Chronic venous insufficiency (leaky leg vein valves) is a common cause of bilateral ankle swelling, especially in people who stand for long periods or are overweight. Pregnancy, certain medications (calcium channel blockers, steroids, NSAIDs), and prolonged sitting during travel (economy class syndrome) also commonly cause foot oedema. Blood tests are usually normal.

Pitting vs non-pitting oedema

Type	What it is	Common causes
Pitting oedema	Leaves a dent when pressed for 5 seconds	Heart failure, kidney disease, liver disease, DVT, pregnancy
Non-pitting oedema	No dent: skin bounces back	Hypothyroidism (myxoedema), lymphoedema

Questions to ask your doctor

Is my swelling one-sided or both sides? (One-sided suggests DVT)
What is my albumin level?
Do I need an echocardiogram (heart ultrasound)?
Is any of my medication causing or worsening swelling?
Do I need compression stockings?

References

Sources cited on this page. PubMed links open the original abstract.

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. PMID 16513004 · doi:10.3122/jabfm.19.2.148

Unilateral versus bilateral swelling – why the distinction matters

The most clinically important initial assessment in a patient with swollen feet or ankles is whether the swelling affects one leg or both. This single observation substantially narrows the differential diagnosis. Bilateral (both legs) symmetrical swelling almost always has a systemic cause: heart failure, liver failure, kidney disease, hypoalbuminaemia, or venous insufficiency affecting both legs equally. Unilateral (one leg) swelling demands urgent consideration of deep vein thrombosis (DVT) – a clot in the leg's deep veins – as well as cellulitis, Baker's cyst rupture, ruptured muscle, or unilateral venous obstruction from lymph nodes or pelvic mass.

In the UK, any unilateral leg swelling without an obvious explanation (such as recent immobilisation, long-haul flight, or trauma) should prompt a Wells DVT probability score followed by a D-dimer blood test and/or compression Doppler ultrasound. A missed DVT carries a risk of pulmonary embolism (PE), which is potentially fatal.

Why heart failure causes ankle and foot swelling

In heart failure, the heart's reduced pumping capacity raises the pressure in the venous system. Elevated venous pressure in the legs means fluid is forced out of capillaries into surrounding tissue more rapidly than it can be reabsorbed – producing pitting oedema. Gravity explains why this begins in the ankles and feet in ambulant patients and shifts to the sacrum in bed-bound patients. Associated features that point towards heart failure include breathlessness (especially lying flat – orthopnoea), a productive cough or frothy sputum, enlarged liver, raised jugular venous pressure (JVP), and a third heart sound.

Medications as a common overlooked cause

Drug-induced oedema is frequently overlooked. The most common culprits are:

Calcium channel blockers (amlodipine, nifedipine, felodipine) – cause peripheral arteriolar dilation, which shifts fluid into the legs. Ankle oedema affects up to 30% of patients on amlodipine at standard doses and is not a sign of heart failure.
NSAIDs – cause sodium and water retention via prostaglandin inhibition in the kidney.
Pregabalin/gabapentin – oedema is a recognised side effect, particularly at higher doses.
Steroids – mineralocorticoid activity causes sodium retention.
Thiazolidinediones (pioglitazone) – significant fluid retention in people with diabetes.

If drug-induced oedema is suspected, the medication should be changed or stopped before escalating investigation or starting diuretics.