Version July 2025
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Why do the lungs fill with fluid when a person has heart failure? —
When you have heart failure, your heart does not pump as well as it should. It does not squeeze or fill as well as it should. As a result, your heart struggles to keep blood moving, but it lags behind. The organs in your body might not get as much blood as they used to, especially when you exercise. Also, fluid builds up in the body.
Fluid can build up in the feet and ankles. That's why people with heart failure sometimes get swollen ankles (figure 1).
Fluid can also build up in the lungs, which can be life-threatening. That's why people with heart failure sometimes have trouble breathing. Fluid in the lungs is the number 1 reason people with heart failure need to go to the hospital. But it is often avoidable.
To keep heart failure from getting worse, and to keep yourself breathing as well as possible, it is very important to keep your body from holding onto extra fluid. That's why it is so important to take your heart failure medicines and look for warning signs of extra fluid.
Why are medicines for heart failure so important? —
Medicines to treat heart failure can help you feel better and live longer. They can help keep fluid out of your lungs and help you breathe better. Missing even 1 dose can make a big difference in how you feel.
One type of heart failure medicine is called a "diuretic" (sometimes called a water pill). It helps the body get rid of extra salt and fluid. That way, fluid is less likely to build up in the ankles, belly, or (most importantly) lungs.
Some people skip their diuretic because they do not like having to go urinate so often. But urinating a lot means the medicine is working, and means your lungs are less likely to fill with fluid.
Ask your doctor or nurse which of your medicines is a diuretic. The most commonly used diuretic for heart failure is furosemide (brand name: Lasix).
What are the symptoms of fluid in the lungs? —
When heart failure is getting worse and you have fluid building up in your lungs, you might have these symptoms:
●Weight gain
●Increased swelling in the feet, ankles, legs, or other body parts
●Increased tiredness or trouble breathing
If you have 1 or more of these symptoms, take action. Your body is telling you things are starting to go wrong.
You and your doctor or nurse should write up a heart failure "action plan" (figure 2 and figure 3). This tells you what to do if you have signs your heart failure is getting worse.
Take your action plan seriously. Keep it on the refrigerator or someplace where you can easily find it. If you follow your action plan closely, you might be able to avoid going to the hospital, and you will know when to call an ambulance to bring you to the hospital.
Why must I weigh myself every day? —
Water is heavy, so your weight will go up if your body is holding onto extra fluid. If you weigh yourself every day, you will know right away when fluid starts to build up. Weight gain can be an early sign your heart failure is getting worse. If you have a weight change, you can take steps to keep the problem from getting worse.
Here's what you should do:
●Weigh yourself every morning after you urinate and before you eat or drink.
●Use the same scale and wear about the same amount of clothing (or wear nothing) every time you weigh yourself.
●Keep a chart near the scale, and write down your weight every day.
●Each time you write down your weight, check if the number has gone up from the day before and the week before. If so, follow your action plan.
For most people, gaining 2 to 3 pounds in 1 day is cause for concern that your body is holding onto extra fluid. Gaining 5 pounds in 1 week is also a bad sign.
Why must I check for swelling every day? —
Swelling is another sign your body is holding onto extra fluid and that your heart failure is getting worse. If any part of your body looks more swollen than usual, don't ignore it, even if you feel normal.
Patient education: Heart failure (The Basics)
Patient education: Heart failure with preserved ejection fraction (The Basics)
Patient education: Heart failure with reduced ejection fraction (The Basics)
Patient education: Medicines for heart failure with reduced ejection fraction (The Basics)
Patient education: Heart failure action plan (The Basics)
Patient education: Swelling (The Basics)
Patient education: Exercise and heart failure (The Basics)
Patient education: Heart failure (Beyond the Basics)
Patient education: Edema (swelling) (Beyond the Basics)
