In Singapore and across Southeast Asia, people often say “water retention” when their feet and legs look puffy by the end of the day. Water retention in feet and legs is common, and the cause ranges from a hot day and a salty meal to a vein, heart, kidney or liver condition. This page explains the likely reasons so you can judge what is ordinary and what needs a doctor. It is educational and cannot diagnose you.
Call 995 for swelling with sudden breathlessness, chest pain, coughing up blood or fainting. Get urgent care the same day for swelling in one leg that is sudden, painful, warm or discoloured, or for swollen skin that is hot, red and spreading with a fever.
What is water retention?
Water retention is a non-medical term. Doctors usually say fluid retention or oedema (see our explainer on edema and oedema). It means extra fluid is sitting in the tissue instead of being carried away by the blood and lymph vessels. In the legs it often looks like puffy feet, tight shoes, sock marks that linger, and a dent that stays briefly after you press the skin.
Everyday reasons for water retention
Many cases of water retention in legs have a simple explanation. Common reasons for water retention include:
- Heat and humidity. Warm weather makes blood vessels widen, so more fluid leaks into the tissue. Tropical climates make this a regular issue.
- Standing or sitting for long periods. Gravity and a lack of calf muscle movement let fluid pool. Long flights and long desk days are classic triggers. See heat, humidity and your veins.
- Salty food. Salt makes the body hold on to water. Hawker meals, instant noodles and sauces can be high in salt.
- Pregnancy. Extra fluid and pressure from the womb on pelvic veins often cause swelling in the later months.
- Hormones. Many women notice more puffiness in the days before a period.
- Weight gain and low activity. Both can slow circulation in the legs.
- Minor injury. A twisted ankle swells on its own side only.
These causes usually ease with movement, rest and raising the legs, and swelling is typically worse in the evening and better in the morning.
What causes fluid retention in the legs: vein problems
If you are asking what causes water retention that comes back every day, weak leg veins deserve a mention. Veins have one-way valves that stop blood falling back down the leg. When valves weaken, blood pools and pressure rises, which pushes fluid into the surrounding tissue. This is called chronic venous insufficiency and is one of the most common medical causes of long-term ankle and foot swelling.
Clues include aching or heavy legs, visible varicose veins, itchy or brownish skin near the ankle, and swelling that improves after a night lying flat. A painless ultrasound scan can show whether the valves are leaking, and treatment is available. Our vein symptom check can help you decide whether to see someone.
Medicines and other medical causes
What causes fluid retention is not always about the veins or lifestyle. Other reasons include:
- Medicines. Some blood pressure tablets, anti-inflammatory painkillers, steroids, some diabetes medicines and hormone treatments can make the ankles swell. Do not stop a prescribed medicine yourself. Speak to your doctor or pharmacist.
- Heart failure. A weaker pump leads to fluid backing up, usually in both legs, often with breathlessness and tiredness.
- Kidney disease. The kidneys may not clear salt and water properly. Morning puffiness around the eyes is a clue.
- Liver disease. Fluid can build up in the legs and abdomen.
- Lymph problems. Lymphoedema is persistent swelling when lymph drainage is damaged or blocked.
- Low blood protein or an underactive thyroid.
- Infection (cellulitis). A red, hot, painful swollen patch, often with fever.
- Blood clot (DVT). Usually one leg, often painful and warm. See deep vein thrombosis.
What is fluid overload?
Fluid overload means the whole body is holding more fluid than it can clear. It often shows as swelling that creeps up the legs, weight gain of a few kilograms over days, a tight or swollen belly, breathlessness when lying flat or after small efforts, and tiredness. It is usually linked to heart, kidney or liver conditions rather than the veins alone and needs medical assessment, not self-treatment.
Clues that help narrow down the cause
| Pattern | Possible meaning |
|---|---|
| Both feet, worse by evening, better in the morning | Heat, gravity, salt or vein valve weakness |
| One leg, sudden, painful, warm | Clot, infection or injury: get checked promptly |
| Both legs with breathlessness or weight gain | Possible heart or fluid overload cause |
| Puffy eyes and legs | Possible kidney cause |
| Started after a new medicine | Possible medicine effect |
This table is a guide only.
What happens at the doctor
Expect questions about when swelling began, whether it affects one or both legs, your medicines, diet and other symptoms. The doctor will check your legs, heart and lungs, and may arrange blood tests, a urine test, a heart scan or a leg vein ultrasound. Treatment depends on the cause. For what you can safely do yourself in the meantime, see how to reduce water retention in legs and the wider guide to swollen ankles. Unfamiliar terms are in the glossary.
When to see a doctor
Call 995 if swelling comes with sudden shortness of breath, chest pain, coughing up blood or fainting.
Seek urgent care the same day if:
- One leg is suddenly swollen, painful, warm or discoloured
- The area is hot, red and spreading, or you have a fever
- You are pregnant and have sudden facial or hand swelling, a severe headache or vision changes
See a doctor soon if swelling is new, keeps returning, is getting worse, does not ease overnight, comes with weight gain over a few days, or you notice skin changes, aching or visible veins. A GP can review your medicines and refer you onward; see find a vein specialist if a vein cause is suspected.
This page is educational and does not replace personal medical advice.
Frequently asked questions
Why do my feet retain water in the evening?
Gravity pulls fluid down the body when you are upright, and heat makes vessels relax so more fluid leaks into the tissue. If it settles overnight and you feel well, it is often harmless. If it happens daily, is worsening or comes with other symptoms, have it checked.
Is water retention in the feet a sign of heart problems?
It can be, but it is not the most common reason. Heart failure causes swelling in both legs, usually with breathlessness, tiredness or trouble lying flat. Swelling alone does not mean a heart problem, and a doctor can tell the difference.
Can salt cause water retention?
A very salty meal can make the body hold more water for a time, which many people notice as puffy feet or fingers. A regular high-salt diet can also add to fluid build-up in people with heart or kidney conditions. HPB advice is to keep salt intake moderate.
What is fluid overload?
Fluid overload means the body is carrying more fluid than it can clear. It can cause swelling, weight gain over days and breathlessness. It is usually linked to heart, kidney or liver conditions and needs medical assessment.
Can varicose veins cause water retention in the legs?
Yes. Weak vein valves let blood pool in the leg, raising pressure in the veins and pushing fluid into the tissue. This is a common cause of ankle swelling that is worse later in the day.
Sources and further reading
This article is general information, not personal medical advice. Please speak to a doctor about your own symptoms. How we create our content.
