What are natriuretic peptide tests (BNP, NT-proBNP)?

Natriuretic peptides are proteins that your heart and blood vessels make. Natriuretic peptide tests measure the amount of these proteins in a sample of your blood. They are mainly used to help confirm or rule out heart failure in people who have symptoms.

Heart failure is also called congestive heart failure. If you have this condition, your heart has trouble pumping enough oxygen-rich blood to meet your body's needs.

Two types of natriuretic peptides can be measured to check for possible heart failure. Your health care provider will decide which of these peptides to test:

• Brain natriuretic peptide (BNP) is a protein that's a type of hormone. A hormone is a chemical messenger in your bloodstream that controls the actions of certain cells or organs. BNP has "brain" in its name because that's where researchers first discovered it. Your heart makes and releases BNP into your bloodstream when it's working harder than normal to pump blood.

  The BNP tells your blood vessels to open wider and your kidneys to get rid of water and salt through urine (pee). This helps reduce the workload on your heart by lowering blood pressure and reducing the amount of blood your heart has to pump.

• N-terminal pro b-type natriuretic peptide (NT-proBNP) is a protein that's an "ingredient" for making the BNP hormone. Like BNP, your heart makes larger amounts of NT-proBNP when it has to work harder to pump blood.

It's normal to have some BNP and NT-proBNP in your bloodstream. But higher than normal levels for your age and sex may be a sign of heart failure.

Other names: brain natriuretic peptide, NT-pro B-type natriuretic peptide test, B-type natriuretic peptide, N terminal proBNP

What are they used for?

A BNP test or an NT-proBNP test is mainly used to help diagnose or rule out heart failure in a person who is having symptoms. Shortness of breath is the most common symptom of heart failure, but other conditions can cause the same type of breathing problems.

If a person with shortness of breath has normal BNP or NT-proBNP levels, heart failure can usually be ruled out. If high BNP or NT-proBNP levels are found, other tests will usually be done to confirm that heart failure is causing the symptoms.

For people who have already been diagnosed with heart failure, the test may be used to:

• Find out how serious their heart condition is
• Predict the chances that their condition will get worse
• Check if an increase in symptoms means that heart failure has gotten worse

In certain cases, the test may also be used to monitor the heart health of people who:

• Have had a heart attack
• Have a heart condition that suddenly reduces the flow of blood to the heart, such as unstable angina

Why do I need a natriuretic peptide test?

You may need a BNP test or an NT-proBNP test if you have symptoms that could mean you have heart failure. These include:

• Feeling short of breath
• Swelling in your abdomen (belly), feet, legs, and/or veins in your neck
• Fatigue and/or general weakness
• Coughing
• Inability to sleep lying flat
• Needing to urinate (pee) a lot, especially at night
• Loss of appetite and nausea

If you have already been diagnosed with heart failure, your provider may order one of these tests to learn more about your condition.

What happens during a natriuretic peptide test?

For a BNP test or an NT-proBNP test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

If you're being tested in a hospital, you may have a fingerstick test. Your finger will be pricked with a small needle and a few drops of blood will be gathered for testing. This method provides quicker results than using blood from a vein.

Will I need to do anything to prepare for the test?

You don't need any special preparations for a BNP test or an NT-proBNP test.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

The meaning of your test results will depend on your age, sex, medical history, family history, and the results of other tests. Ask your provider to explain what the results of your BNP or NT-proBNP test say about your health and how this information may affect your treatment.

A BNP or NT-proBNP test alone can't diagnose the cause of your symptoms. But in general, if you have symptoms that could be caused by heart failure:

• Normal results on a BNP or NT-proBNP usually mean that you're unlikely to have heart failure. Your provider may order other tests to find out what's causing your symptoms.

  If you have obesity, your weight may affect the accuracy of your test results, making your levels lower than they really are. If your provider suspects heart failure, you may have other heart health tests even if your BNP or NT-proBNP levels are normal.

• Higher than normal levels of BNP or NT-proBNP mean that you could have heart failure. Your provider will probably order other heart health tests to help make a final diagnosis.

In most cases, the higher the level of your test results, the more serious your heart failure may be. But other health conditions can increase BNP and NT-proBNP levels. That's why your medical history is important for understanding whether high test results mean you have heart failure.

Other conditions that can cause high levels of BNP and NT-proBNP include:

• Kidney failure
• Other types of heart disease, including conditions that affect your heart valves or heart muscle
• Certain lung disorders, including a blood clot in your lung (pulmonary embolism) and high blood pressure in your lungs (pulmonary hypertension)

If you have questions about your results, talk with your provider.

Learn more about laboratory tests, reference ranges, and understanding results