B-type Natriuretic Peptide (BNP) Test
What is a B-type natriuretic peptide (BNP) test?
A B-type natriuretic peptide (BNP) test is a blood test. It measures the levels of a certain type of hormone in your blood called a B-type natriuretic peptide. This test gives your healthcare provider information about your heart.
Higher-than-normal levels of BNP in your blood can be a sign that your heart isn’t working as it should. It can mean that your heart isn’t pumping enough blood through your body. Since BNP is cleared by your kidneys, it may also mean that your kidneys are not functioning properly.
Some laboratories offer a similar test called “aminoterminal pro B-type natriuretic peptide” (or NT-proBNP). Both the BNP and NT-proBNP tests show similar information, although the absolute values of NT-proBNP are about five to 10 times higher than BNP.
Providers use a BNP or an NT-proBNP test to diagnose heart failure. If you already know you have heart failure, your provider may order this test to check the severity (seriousness) of your condition. They may also use this test to monitor how heart failure treatments are working. In some cases, your provider may also order it if they think you may be at higher risk of developing heart failure.
When is a B-type natriuretic peptide (BNP) test performed?
Symptoms of heart failure include:
- Cough that seems dry or “hacking” and gets worse when laying down.
- Difficulty breathing, shortness of breath (dyspnea) or wheezing.
- Delirium (confusion).
- Dizziness or fainting (syncope).
- Fatigue or feeling sluggish.
- Heart palpitations.
- Nausea and vomiting or loss of appetite.
- Swelling (edema) in your abdomen, legs, ankles and feet.
- Urinating (peeing) more than usual at night (nocturia).
Heart failure means your heart isn’t pumping blood as it should. It doesn’t mean that your heart has failed or stopped working entirely. If your provider has already diagnosed you with heart failure, they may order a BNP or NT-proBNP test to monitor how treatments are working.
Get emergency medical help if you have these symptoms. Heart failure is life-threatening and requires immediate treatment.
What is BNP?
BNP is one of several proteins that help regulate blood circulation throughout your body. Even though your heart makes this protein, providers sometimes call it “brain” natriuretic peptide because it was first discovered in brain tissue.
As part of your circulatory system, your heart and blood vessels pump oxygen-rich blood to your muscles, organs and other tissues. The left ventricle (one of the heart’s four chambers) pumps a great deal of blood through the heart and it goes on to flow through your body.
The left ventricle is one of the main organs that make BNP. As your heart stretches due to increasing load or experiences increased stress from injury, BNP levels rise. Your heart muscle cells respond to such stress by secreting BNP to unload your heart, which prompts your kidneys to relieve salt and water (hence the name “natriuretic”).
How does a BNP test or NT-proBNP test work?
A BNP test or NT-proBNP test detects heart failure by measuring the amount of BNP or its prohormone NT-proBNP in the bloodstream, respectively. High levels of BNP or NT-proBNP are a sign that the heart has to work too hard to pump blood.
What should I expect during a BNP test or NT-proBNP test?
You don’t need to do anything to prepare for a BNP test or NT-proBNP test. Your provider will clean your arm and insert a needle. Your provider removes some of your blood through a vein. The needle may pinch or sting. But it shouldn’t hurt.
A lab examines your blood and checks the levels of BNP or NT-proBNP. Your provider will let you know when the results are ready.
What should I expect after a BNP or NT-proBNP test?
After taking a blood sample, your provider will place a bandage on your arm. You may be a little sore in the area where the needle entered your arm. You may have a small bruise. When the results are ready, your provider will let you know and discuss the next steps.
What are the benefits of a BNP or NT-proBNP test?
Using just a small amount of blood, this test gives your provider important information about your heart health. A BNP or NT-proBNP test helps your provider diagnose heart failure and rule out other health conditions that cause similar symptoms. The results of a BNP test or NT-proBNP test also allow your provider to plan treatments and monitor how well they’re working.
What are the risks of a BNP test?
Blood tests are very common and safe. Your provider only needs a small amount of blood for this test. After the test, your body naturally replenishes your blood supply. Some people feel a little dizzy or lightheaded after a blood test.
Results and Follow-Up
When should I know the results of a BNP test?
Providers often do this test in the emergency room or hospital when you’re having symptoms of heart failure. It’s important to diagnose heart failure accurately (and rule out other possible conditions) so you can start treatment as soon as possible.
That means you’ll probably get your results right away, usually in under 15 minutes. Your provider will let you know when to expect results and explain what they mean.
What do abnormal levels of BNP mean?
For people who don’t have heart failure, normal BNP levels are less than 100 picograms per milliliter (pg/mL). BNP levels over 100 pg/mL may be a sign of heart failure.
For NT-proBNP, normal levels are less than 125 pg/mL for people under 75 years old and less than 450 pg/mL for people over age 75. NT-proBNP levels over 900 pg/mL may be a sign of heart failure.
Every person has their own range of BNP or NT-proBNP level range. Ask your provider about the specific measurements of your BNP test or NT-proBNP test.
Heart failure medications, including beta blockers, ACE inhibitors and diuretics, can lower BNP or NT-proBNP levels in the blood. If you’re taking these drugs to treat heart failure, your BNP or NT-proBNP test results may be lower than if you’re not taking them. Your levels can also be lower if you have obesity or kidney failure.
Depending on the results of the BNP test, your provider may order follow-up tests, such as an electrocardiogram (EKG or ECG). This test monitors your heart rate through sensors attached to your skin. It can help your provider diagnose or evaluate heart failure and other heart problems.
When should I call my doctor about a BNP or NT-proBNP test?
Call your provider if you have any questions about the results of the BNP blood test. Your provider will explain the results. They’ll also recommend follow-up tests or treatments.
A note from Cleveland Clinic
A B-type natriuretic peptide (BNP) test or aminoterminal pro B-type natriuretic peptide (NT-proBNP) test gives your provider essential information about your heart health. It helps them diagnose heart failure, so they can develop a treatment plan. It also helps them monitor how well treatments are working. Talk to your provider if you have any questions about the test results. If you’ve received a heart failure diagnosis, there are things you can do to live with heart failure, including lifestyle and dietary changes.
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