Health Encyclopedia

BNP (Blood)

Does this test have other names?

B-type natriuretic peptide

What is this test?

This test looks for the protein BNP in your blood. BNP is made inside the pumping chambers of your heart when pressure builds up from heart failure. The test is an important tool for doctors to diagnose heart failure quickly.

Heart failure occurs when your heart is not pumping blood well. This causes cells inside your heart to release BNP, which opens up blood vessels in your body to take pressure off your heart. A BNP blood test correctly indicates heart failure about 90 percent of the time.

The BNP test can help your doctor diagnose heart failure, plan treatment, evaluate how well the treatment is working, and determine when it is safe for you to leave the hospital. The BNP test can show how serious your heart failure is now and how severe your heart failure will be in the future. A BNP test is quite accurate and it only takes about 15 minutes to get the results. 

Why do I need this test?

You may need this test if your doctor suspects that you have heart failure.

The main symptom of heart failure is difficulty breathing, or dyspnea. If you go to your doctor's office or the emergency room with trouble breathing, your doctor will want to know the cause as quickly as possible. Many conditions can cause breathing difficulties, but if you also have a blood test that is positive for BNP, heart failure is likely causing your symptoms.

You may also need this test so that your doctor can see how well the your heart failure therapy is working. 

What other tests might I have along with this test?

You may have a blood test called ANF. ANF is a protein similar to BNP, but it is made in a different part of the heart. You may also have other blood tests, a chest X-ray, an electrocardiogram, or an echocardiogram, which is an ultrasound of the heart. 

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

BNP is measured in picograms per milliliter (pg/mL) or nanograms per liter (ng/L). Less than 100 pg/mL is considered normal. In general, the more serious your heart failure, the higher your levels of BNP will be.

According to some experts on heart failure:

  • BNP under 100 pg/mL means that you have a 96 percent chance that your symptoms aren't caused by heart failure.

  • BNP above 100 pg/mL means you have a 90 percent chance that your symptoms are caused by heart failure.

  • BNP above 700 pg/mL may mean serious heart failure that should be treated in the hospital.

  • If your BNP has gone below 500 pg/mL after treatment, it may mean that you are ready to leave the hospital. 

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore. 

What might affect my test results?

Other things besides heart failure can cause your BNP to rise, including:

  • Kidney failure or being on dialysis

  • Long-term, or chronic, heart failure

  • Nesiritide (Natrecor), a synthetic form of BNP used to treat heart failure

How do I get ready for this test?

You don't need t prepare for this test.