What causes swollen ankles and feet? 

Swollen ankles and feet are the result of fluid building up in your body’s tissues.

It is known medically as ‘peripheral oedema’ – but you may hear healthcare professionals referring to it as ‘fluid retention’ and ‘water retention’ too.

This article unpicks the causes, when to seek medical help and what to do to help ease the swelling.

Why are my ankles and feet swollen?

There are many causes of swollen ankles and feet, ranging from lifestyle factors and incidents that cause mild and often harmless swelling, to persistent or sudden swelling that can be a sign you have a serious heart or other medical condition.

Lifestyle

Lifestyle is the most common reason for swollen ankles and feet. This includes eating too much salty food like ultra-processed foods, such as snack bars and ready-made meals, and being inactive, such as:

• Sitting in a chair all day, if you find moving around difficult.
• Standing for many hours, maybe because of your job.
• Travelling for long periods, such as on a long-haul flight.

Puffiness and swelling in the ankles and feet is caused by an accumulation of extra fluid in the tissues.

A high-salt diet can cause this because the excess salt makes the body hold onto water, which increases the total amount of fluid in your body.

This fluid then leaks out of the blood vessels and builds up in the surrounding tissue, particularly in the lower part of the body.

When you are inactive, fluid collects in your legs, ankles and feet due to the natural forces of gravity pulling it down.

And because you’re not moving, the muscles in your calves and feet that help pump blood back to your heart are not activated either, and your lymphatic system stops working properly too. Both of these lead to fluid accumulating in your legs, ankles and feet.

Other one-off lifestyle causes of swelling include injuries, like sprains, insect bites and infections.

Medicines

Certain medicines including blood pressure drugs, hormone therapies, contraceptives, antidepressants and steroids can trigger swelling too. Your doctor can adjust your medicines if this is an issue.

Medical conditions

But if swelling in your ankles and feet is persistent, or sudden and severe, it can be a sign you have a heart condition, like heart failure, or a problem with your kidneys, liver or circulatory system.

Read more about heart failure in the next section.

How does heart failure cause swollen ankles and feet?

Heart failure is linked to swollen ankles and feet because the heart muscle is too weak or stiff to pump blood around your body properly.

It can be one of the first signs of heart failure and can be an ongoing symptom of the condition.

If you’ve been diagnosed with heart failure, your doctor may ask you to monitor swelling in your ankles and feet as an indicator of how well your heart is pumping, or how well any medication you’ve been prescribed is working.

The reason your ankles and feet swell with heart failure is because blood backs up in the veins of the legs and feet when your heart is not working properly. This increases blood pressure in your blood vessels that forces fluid into the surrounding tissues, leading to swelling.

The build-up of fluid in the tissues is made worse because in response the body tries to increase the volume of blood in the blood vessels by holding salt and water in the blood. But instead of helping this leads to more fluid building up in the tissues.

This is why heart failure can also affect the kidneys whose job it is to balance the amount of fluid and salt in your body.

Eating a high-salt diet and being inactive when you have heart failure can worsen the swelling in your ankles and feet – so it’s important to have a healthy lifestyle.

If you have been diagnosed with heart failure and notice new or worsening swelling in your legs, ankles or feet, contact your medical team as your medicines or treatment plan may need adjusting.

What other health conditions can cause swollen ankles and feet?

Swelling in the legs, ankles and feet could be a sign you have a problem with your kidneys or liver, which both help regulate fluid in your body.

It can also indicate a circulatory problem such as a blood clot in a vein in your leg – known as a deep vein thrombosis (DVT). This can be a medical emergency if accompanied by breathlessness and chest pain and you need to call 999.

Another cause is lymphoedema, when a blockage or damage to the lymphatic system prevents lymph fluid from draining properly.

Pregnancy also sees the body hold more fluid, and the growing womb adds pressure to the circulatory system, reducing blood flow in the legs which can lead to fluid buildup in the feet and ankles.

When are swollen ankles and feet dangerous?

Although mild swelling is often harmless, you should seek urgent medical care if you experience any of the following:

• Sudden or severe swelling in one leg, especially if painful, red, or warm, this may indicate a DVT.
• Swelling in both legs with breathlessness, chest pain, or fatigue as this could be heart failure or another heart issue.
• Rapid weight gain or swelling that worsens within days.
• Tight, shiny, or discoloured skin, or the development of ulcers.
• Persistent swelling that does not improve with rest or leg elevation.
• Yellow skin or dark urine, as this may suggest you have a liver or kidney problem.

What can I do to get rid of swollen ankles and feet?

Treating the underlying cause of your swollen ankles and feet is key whether it’s a serious medical condition like heart failure, or lifestyle related such as eating a diet high in salt or not being physically active.

If you have heart failure your medical team will prescribe medicines to help your heart pump more effectively, as well as medicines to help remove fluid from your tissues called diuretics – often referred to a ‘water pills’.

• Read more about medicines for heart conditions.

Being more active – even if it’s simply sneaking 10 minutes of movement here and there into your day – is important to help prevent swelling in your legs, ankles and feet, as is having a low-salt diet.

There are also a few simple things you can do yourself to help reduce swelling and discomfort if your ankles and feet are swollen. Here are 5 helpful tips:

1. Elevate your legs: lie or sit down and raise your legs above the level of your heart using pillows or a footstool to help fluid drain away from your legs.
2. Massage your legs: gently massaging upwards from the ankles can help stimulate circulation and move excess fluid.
3. Exercise gently: walking or light stretching improves circulation and helps move fluid that’s trapped in your tissues.
4. Wear loose, comfortable clothing and shoes: avoid anything that sits tightly on your body as it could restrict blood flow, and choose supportive shoes with soft soles and low heels.
5. Use compression socks: these can help push fluid upwards towards your heart, but speak to your GP before getting medical-grade versions as these need to be professionally fitted.

Swollen ankles and feet are common and often temporary, particularly after sitting or standing for long periods, when travelling or in warm weather.

However, persistent or sudden swelling especially when accompanied by shortness of breath, fatigue, or pain may point to a heart, kidney, liver or circulatory problem that requires prompt medical attention by urgently seeing your GP or calling 111 or 999.

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