Both ankles swelling is usually a slower, less alarming story than one leg — but “less urgent” is not “unimportant”. Symmetrical swelling is how the heart, the kidneys, the liver and a long list of medicines first announce themselves.
Swelling in both legs that needs prompt attention
- With breathlessness, especially lying flat or waking you at night — call 911 for sudden breathlessness or chest pain
- Coming on over days rather than months, or getting rapidly worse
- With significant weight gain over a short period
- With a break in the skin, weeping, or spreading redness
- With reduced urine output, or new confusion
The pattern that tells you most
Does it clear overnight? Swelling that is obvious by evening and largely gone by morning is behaving like a gravity-and-venous problem. Swelling that is still there when you get up has usually moved past that, and points toward a systemic cause or an established lymphatic component.
How far up does it go? Ankles only is different from ankles and shins, which is different again from swelling that reaches the thighs or the abdomen. The higher it climbs, the more it suggests a whole-body fluid problem rather than a local one.
The common causes, roughly in order
Gravity and time on your feet
Long periods standing or sitting — a shift on your feet, a long flight, a desk day without moving. Both ankles, worse by evening, gone by morning, no other findings. Extremely common and benign.
Chronic venous insufficiency
Leaky vein valves on both sides. Soft, pitting, worse standing, better elevated, often with visible veins, itching, or brown staining above the ankles. More →
Medicines
One of the most common causes and the easiest to miss. Several widely prescribed classes can cause or worsen ankle swelling — some blood pressure medicines, some diabetes medicines, steroids, certain hormone treatments and several anti-inflammatories among them. The timing is the clue: swelling that started within weeks of a new prescription or a dose change. More →
Heart
When the heart cannot clear returning blood efficiently, pressure backs up and fluid collects in the lowest parts of the body. Usually both legs, often creeping upward, and typically with breathlessness — on exertion, lying flat, or waking you at night — and sometimes rapid weight gain.
Kidneys
Kidney disease causes salt and water retention, and protein loss into the urine lowers the blood protein that holds fluid in the vessels. Swelling can be more generalized, including puffiness around the eyes in the morning, and urine may look frothy.
Liver
Advanced liver disease reduces albumin production and raises pressure in the abdominal veins. Leg swelling often comes with abdominal swelling.
Thyroid
An underactive thyroid can produce a firmer, non-pitting swelling, usually alongside fatigue, cold intolerance and dry skin.
Other
Pregnancy, obesity, heat, high salt intake, low blood protein from poor nutrition, and lymphatic problems affecting both sides.
The most useful thing you can do before the appointment
Bring your complete medicine list with doses, and note roughly when the swelling started. A medication cause is frequently found this way and is frequently fixable — but only if someone can line up the two timelines. Do not stop anything on your own; some of these medicines are preventing considerably more serious problems than a puffy ankle.
What an assessment involves
- History: how long, how high it reaches, whether it clears overnight, what medicines, what else you have.
- Examination of both legs, plus heart and lungs.
- Blood tests where the picture suggests it — kidney, liver, thyroid, and heart markers.
- Urine testing for protein.
- An arterial check before any compression is considered.
- Ultrasound, echocardiogram or referral depending on where the findings point.
What helps while it is being worked out
- Elevation above heart level for periods through the day — the height matters more than the duration, and a footstool barely counts.
- Movement. Walking and ankle circles use the calf pump; standing still is the worst option.
- Avoid prolonged standing where you can, and break up long sitting.
- Do not start compression until someone has checked your arterial circulation. Why →
- Do not take someone else’s water tablets. Diuretics are appropriate for some causes and unhelpful or harmful for others.
Common questions
Is swelling in both legs less serious than one?
Less time-critical, generally — a clot is far less likely when both legs are affected equally. But the causes on the both-legs list include heart, kidney and liver disease, so it is a different kind of serious rather than a lesser one. Persistent or worsening swelling in both legs deserves a proper look.
Why is it worse in hot weather?
Heat dilates blood vessels, which increases the fluid pushed out into the tissue, and people tend to be less active and more dehydrated. Seasonal worsening on its own is common and not alarming — but it should not be used to explain away swelling that is also getting worse year on year.
Should I cut down salt?
Reducing very high salt intake often helps, and is sensible generally. Large unsupervised changes to salt or fluid intake can interact with heart, kidney and blood pressure medicines, so if you are on any of those it is worth raising rather than experimenting.
My swelling does not pit. Does that change things?
It shifts the likely causes — non-pitting swelling points more toward lymphatic involvement or thyroid disease than toward simple fluid overload. It does not make it milder. More on what pitting does and does not tell you →
Where to go next
Sources
- NHS. Oedema.
- Society for Vascular Surgery. Chronic Venous Insufficiency.
- NHS. Lymphoedema.
Written by Tom Biernacki, DPM, FACFAS. Published 21 September 2026. General education, not medical advice.