Heart Failure Symptoms and Causes: Warning Signs, Diagnosis, and Treatment

Heart Failure Symptoms: What to Know

This section keeps the useful search intent from the older Heart Failure Symptoms: What to Know article and brings it into this main guide.

The most important point is simple. Heart failure can look different from one person to another. The symptoms can also look like lung disease, kidney disease, anemia, infection, thyroid disease, or medicine side effects.

Do not try to diagnose heart failure from one symptom. A doctor may need your history, an exam, blood tests, an ECG, and an echocardiogram.

If you already have heart failure, watch for changes from your normal. A small change can matter more than a single number.

Signs Heart Failure May Be Getting Worse

People with diagnosed heart failure should know their personal action plan.

Contact your care team when you notice a clear change such as:

• more breathlessness during normal activity
• new breathlessness at rest
• needing more pillows to sleep
• waking breathless at night
• more swelling in the feet, legs, hands, or belly
• a sudden weight change
• a tighter waistband, shoes, or rings
• more cough or wheeze
• less urine
• new dizziness
• more tiredness or weakness
• poor appetite or nausea
• new palpitations
• a clear drop in walking or daily activity

The American Heart Association notes that some people are told to report a gain of more than two or three pounds in one day, or more than five pounds in one week. Your own threshold may be different. Follow your personal plan.

For broader heart education, visit the Heart and Cardiovascular Health Hub.

Main Heart Failure Symptoms Explained

1. Shortness of Breath

Shortness of breath may happen during walking, climbing stairs, chores, bending, or rest. It may happen because fluid backs up in the lungs or because the heart cannot meet the body's needs.

Lung disease, anemia, infection, low fitness, and other problems can cause the same symptom. Sudden or severe breathlessness needs urgent assessment.

2. Trouble Breathing When Lying Flat

Some people breathe worse when they lie flat. This is called orthopnea. They may need extra pillows or may sleep in a chair.

New or worsening trouble breathing while flat should be reported to a healthcare professional.

3. Waking Breathless at Night

Some people wake from sleep with strong breathlessness and need to sit or stand. This is sometimes called paroxysmal nocturnal dyspnea.

Sleep apnea, asthma, reflux, lung disease, and panic can also cause night symptoms. A medical review can help find the cause.

4. Swelling in the Feet, Ankles, Legs, or Belly

Fluid retention can cause swelling in the feet, ankles, legs, hands, or abdomen.

Heart failure is not the only cause. Kidney disease, liver disease, vein problems, pregnancy, and some medicines can also cause swelling.

5. Sudden Weight Change

Fast weight gain can be a sign of extra fluid. Weight loss can occur with poor appetite, muscle loss, or advanced illness.

A trend matters more than one isolated reading.

6. Fatigue and Weakness

Heart failure can make normal tasks feel harder. Shopping, stairs, walking, or carrying groceries may take more effort.

Fatigue can also come from anemia, poor sleep, kidney disease, depression, infection, or medicine effects.

7. Cough or Wheeze

A dry cough or wheeze can happen, especially at night or when lying down. Pink or frothy mucus with strong breathing trouble is an emergency sign.

8. Fast or Irregular Heartbeat

You may feel racing, pounding, fluttering, or skipped beats.

Seek urgent care if palpitations come with chest pain, fainting, severe dizziness, or severe breathlessness.

9. Poor Appetite, Nausea, or Early Fullness

Fluid in the belly and changes in blood flow can make a person feel full early. Nausea and low appetite can also happen.

Long lasting poor intake needs review because it can lead to weakness and weight loss.

10. Trouble Thinking or New Confusion

Low blood flow, low oxygen, low sodium, kidney problems, infection, or medicine effects can cause confusion.

Sudden confusion is an emergency.

11. Lower Exercise Ability

A person may walk less far, need more breaks, avoid stairs, or stop normal hobbies.

Watch for change from your own normal level.

What Does Heart Failure Mean in 2026?

Heart failure is a clinical syndrome. It happens when a heart problem leads to symptoms, signs, or both.

The heart may be weak. It may be stiff. A valve may be damaged. The rhythm may be abnormal. Pressure inside the heart may be too high.

The 2026 Second Universal Definition of Heart Failure keeps the four stage path from risk to advanced disease. It also gives more focus to early detection and Stage B, often called pre heart failure.

The 2026 definition also moves away from using rigid ejection fraction cut points as the only way to define heart failure. It groups people into heart failure with reduced ejection fraction, preserved ejection fraction, and improved ejection fraction. Treatment guidelines and clinical trials may still use numeric values, so your clinician may still discuss exact percentages.

What Causes Heart Failure?

Heart failure causes vary. Heart failure often starts because another condition damages or overworks the heart.

• coronary artery disease
• a previous heart attack
• long-term high blood pressure
• heart valve disease
• cardiomyopathy
• abnormal heart rhythms
• myocarditis
• congenital heart disease
• diabetes
• chronic kidney disease
• sleep apnea
• thyroid disease
• heavy alcohol use
• stimulant drugs
• some cancer treatments
• pregnancy related cardiomyopathy
• amyloidosis and other infiltrative disease

Finding the cause matters because some treatment is aimed at the cause itself.

High blood pressure is one important risk. Read How to Lower Blood Pressure Safely for more detail.

Heart Failure Stages and Types

Stage A

A person is at risk but does not have symptoms or known structural heart disease.

Stage B

This is pre heart failure. There may be heart structure changes, abnormal function, or biomarkers, but no current heart failure symptoms.

Stage C

There is current or past heart failure symptoms with structural or functional heart disease.

Stage D

This is advanced heart failure. Symptoms may be severe even with full treatment.

Heart Failure With Reduced Ejection Fraction

Ejection fraction is the share of blood pushed out of the left ventricle with each beat. Reduced ejection fraction means pumping strength is lower.

Heart Failure With Preserved Ejection Fraction

The heart may pump out a normal-looking share of blood but still fill poorly or work under high pressure.

Heart Failure With Improved Ejection Fraction

Some people start with reduced heart function and improve with treatment. Improvement does not always mean the disease is gone. Do not stop medicine unless the care team tells you to do so.

How Is Heart Failure Diagnosed?

Heart failure diagnosis is not made from symptoms alone.

Medical History and Exam

A clinician may ask about breathlessness, swelling, sleep position, weight change, exercise ability, heart disease, family history, alcohol, medicines, and drug exposure.

BNP or NT proBNP Blood Test

A BNP blood test or NT proBNP test can support the diagnosis. These markers can rise when the heart is under strain.

Age, kidney function, body size, rhythm problems, and other health issues can change the result. One number does not diagnose heart failure by itself.

ECG

An ECG checks the heart's electrical activity. It can show rhythm problems or clues to old heart damage.

Echocardiogram

An echocardiogram uses sound waves to look at heart size, movement, valves, filling, and pumping.

Other Tests

Some people may need a chest X ray, blood count, kidney tests, liver tests, thyroid tests, iron tests, cardiac MRI, rhythm monitoring, stress testing, coronary artery testing, sleep testing, or genetic testing.

For more on medical testing, visit the Medical Tests and Screenings Hub.

How Is Heart Failure Treated?

Heart failure treatment depends on the cause, symptoms, blood pressure, kidney function, heart rhythm, pregnancy status, and other health problems.

Treatment may include:

• guideline-directed medicine
• diuretics for extra fluid
• blood pressure treatment
• diabetes and kidney care
• treatment for abnormal rhythm
• valve or coronary procedures
• pacemakers or defibrillators for selected people
• cardiac rehabilitation
• iron treatment in selected people
• sleep apnea treatment when needed
• advanced heart failure care, including mechanical support or transplant evaluation for selected people
• palliative care to support symptoms and quality of life at any stage when useful

Heart Failure Medicines

Heart failure medicines are chosen for the type of heart failure and the person's full health picture.

Core Medicines for Reduced Ejection Fraction

The 2022 AHA, ACC, and HFSA treatment guideline remains a key United States treatment guide. For many people with reduced ejection fraction, four medicine groups form the base of treatment:

• an ARNI, or an ACE inhibitor or ARB when appropriate
• an evidence based beta blocker
• a mineralocorticoid receptor antagonist
• an SGLT2 inhibitor

Diuretics

Diuretics help remove extra sodium and water. They can reduce swelling and lung congestion.

Too much can lead to low blood pressure, dehydration, kidney problems, or changes in sodium and potassium.

Preserved Ejection Fraction

Treatment may include diuretics for congestion, SGLT2 inhibitors when appropriate, and strong care for blood pressure, atrial fibrillation, diabetes, obesity, kidney disease, sleep apnea, and coronary disease.

Never start, stop, double, or share prescription heart medicine based on an online article.

Daily Weight and Symptom Tracking

Daily weight monitoring can help some people spot fluid buildup early.

Your care team may ask you to track:

• weight
• blood pressure
• heart rate
• swelling
• breathlessness
• sleep position
• fluid intake
• diuretic use
• walking or exercise ability

How to Weigh Yourself

• use the same scale
• weigh at about the same time each day
• morning is often used
• wear similar clothing
• weigh after using the toilet and before breakfast when practical
• write the result down

Use the action level given by your own care team.

Sodium, Fluid, and Potassium Safety

Sodium

Too much sodium can make fluid retention worse in some people.

Common sources include processed meat, canned soup, sauces, packaged snacks, ready meals, cheese, and restaurant food.

There is no single sodium target that fits every person with heart failure. Use the amount your care team gives you.

Fluid

Not everyone with heart failure needs the same fluid limit. Some people need one. Others do not.

Do not force extra water to flush out swelling. Do not restrict fluid without medical advice.

Potassium

Heart failure medicine can raise or lower potassium. Kidney function also matters.

Do not use potassium supplements or potassium-based salt substitutes unless a clinician says they are safe for you.

Exercise and Cardiac Rehabilitation

Many people with stable heart failure can benefit from movement.

Cardiac rehabilitation can help some people build fitness in a safer, guided way.

Ask your care team:

• Is exercise safe for me now?
• Should I join cardiac rehabilitation?
• What type of exercise is best?
• How hard should I exercise?
• What symptoms should make me stop?

Stop activity and seek help for chest pain, fainting, severe breathlessness, severe dizziness, or a dangerous new heartbeat feeling.

Over the Counter Medicine and Supplement Safety

Some common products can make heart failure harder to control.

Ask a doctor or pharmacist before using:

• ibuprofen, naproxen, and other NSAIDs
• cold and sinus decongestants
• high sodium effervescent products
• herbal water pills
• licorice root
• potassium supplements
• potassium salt substitutes
• stimulant weight loss products
• energy supplements

Do not stop a prescribed medicine because you read about a side effect online. Contact the prescriber.

Pregnancy and Heart Failure

Pregnancy changes blood volume and heart workload.

Heart failure can happen in people with known heart disease. It can also occur with pregnancy-related cardiomyopathy.

Seek urgent care for severe or fast worsening breathlessness, chest pain, fainting, rapid swelling, or palpitations with severe symptoms.

Not every heart failure medicine is safe during pregnancy or breastfeeding. Specialist care is important.

For related women's health guidance, visit the Women's Health Hub.

Can Heart Failure Be Prevented?

Not every case can be prevented. But risk can often be lowered.

• control high blood pressure
• treat coronary artery disease
• manage high cholesterol
• manage diabetes
• protect kidney health
• do not smoke
• avoid stimulant drugs
• limit or avoid alcohol when advised
• stay active
• treat sleep apnea when present
• take medicine as prescribed
• keep follow up visits

For a wider prevention guide, read Heart Health 101.

Common Heart Failure Myths

Myth: Heart Failure Means the Heart Has Stopped

No. Heart failure is not cardiac arrest.

Myth: Swollen Ankles Always Mean Heart Failure

No. Many other conditions can cause swelling.

Myth: A Normal Ejection Fraction Rules Out Heart Failure

No. A person can have heart failure with preserved ejection fraction.

Myth: Everyone Needs the Same Fluid Limit

No. Fluid advice is personal.

Myth: Everyone Needs the Same Sodium Limit

No. Use the target given by your care team.

Myth: More Water Flushes Out Heart Failure Swelling

No. Extra fluid can make congestion worse in some people.

Myth: Feeling Better Means Medicine Can Stop

No. Treatment may be the reason you feel better.