A brain natriuretic peptide (BNP) test measures the amount of the BNP hormone in your blood. BNP is made by your heart and shows how well your heart is working. Normally, only a low amount of BNP is found in your blood. But if your heart has to work harder than usual over a long period of time, such as from heart failure, the heart releases more BNP, increasing the blood level of BNP. The BNP level may drop when treatment for heart failure is working.
Why It Is Done
The brain natriuretic peptide (BNP) test is used to:
- Check for heart failure. A doctor may think you have heart failure if you are having problems such as trouble breathing and swelling (edema) in the arms or legs.
- Find out how severe heart failure is.
- Check the response to treatment for heart failure.
How To Prepare
You may be asked to not eat or drink anything except water for 8 to 12 hours before having a BNP test.
Your doctor may tell you to stop taking certain heart medicines before this test. Follow your doctor's instructions exactly.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).
How It Is Done
The health professional drawing your blood will:
- Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
- Clean the needle site with alcohol.
- Put the needle into the vein. More than one needle stick may be needed.
- Attach a tube to the needle to fill it with blood.
- Remove the band from your arm when enough blood is collected.
- Apply a gauze pad or cotton ball over the needle site as the needle is removed.
- Apply pressure to the site and then a bandage.
How It Feels
You may feel nothing at all from the needle puncture, or you may feel a brief sting or pinch as the needle goes through the skin. Some people feel a stinging pain while the needle is in the vein. But many people do not feel any pain (or have only minor discomfort) once the needle is positioned in the vein. The amount of pain you feel depends on the skill of the health professional drawing the blood, the condition of your veins, and your sensitivity to pain.
There is very little risk of complications from having blood drawn from a vein.
- You may develop a small bruise at the puncture site. You can reduce the risk of bruising by keeping pressure on the site for several minutes after the needle is withdrawn.
- In rare cases, the vein may become inflamed after the blood sample is taken. This condition is called phlebitis and is usually treated with a warm compress applied several times daily.
- Continued bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can also make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicines, tell your health professional before your blood is drawn.
Normal BNP values are higher in women than in men. BNP values normally increase with age but may stay within a normal range unless heart failure is present.
The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
The amount of a related substance, called N-terminal pro brain-natriuretic peptide (NT-proBNP), may be measured instead of BNP. The results from the NT-proBNP test are different than those from the BNP test but provide similar information. Normal values for NT-proBNP are less than 400 pg/mL or less than 400 ng/L.1
A high value of BNP in the blood:
- Means an increased amount of fluid or high pressure inside the heart.
- May be used to help determine the severity of heart failure.
- May mean a higher chance of death in people with heart failure.
- May show early heart failure in people on kidney dialysis.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- Having lung disease, such as emphysema or chronic obstructive pulmonary disease (COPD).
- Having kidney disease, kidney dialysis, or a heart attack.
What To Think About
- The BNP level may get lower if treatment for heart failure is working. But the BNP level may stay above the normal BNP level even when a heart failure treatment is working well. Your doctor will use your physical exam and other tests, along with your BNP level, to make sure your treatment is working.
Other Works Consulted
Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.
Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
Wilson Tang WH, et al. (2007). National Academy of Clinical Biochemistry laboratory medicine practice guidelines: Clinical utilization of cardiac biomarker testing in heart failure. Circulation, 116(5): e99-e109.
Yancy CW, et al. (2013). 2013 ACCF/AHA Guideline for the management of heart failure: A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Journal of the American College of Cardiology, 62(16): e147-e239.
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Specialist Medical ReviewerStephen Fort, MD, MRCP, FRCPC - Interventional Cardiology
Current as ofAugust 7, 2015