A BNP (brain natriuretic peptide) test is a blood test that measures levels of a protein called BNP that is made by your heart and blood vessels. BNP levels go up when the heart cannot pump the way it should, and a result greater than 100 pg/mL is abnormal. The higher the number, the more likely heart failure is present and the more severe it is. A normal BNP level makes heart failure less likely, freeing doctors to hunt for other conditions that may be causing shortness of breath or fluid retention.

The normal range for BNP is less than 100 pg/mL. A BNP between 100-400 pg/mL may be considered a “gray zone,” and a diagnosis depends on a careful physical examination and additional testing to determine the cause. A BNP greater than 400 pg/mL indicates that heart failure is likely. However, other conditions can also cause high BNP levels, such as kidney failure, pulmonary embolism, pulmonary hypertension, severe infection (sepsis), and lung problems.

It is important to note that BNP levels alone cannot diagnose heart failure, and a diagnosis requires a careful physical examination and additional testing. If you have signs of heart failure, such as shortness of breath and swelling of your legs or abdomen, you may need a BNP test to help make sure the problems are due to your heart and not your lungs, kidneys, or liver. If you have a BNP level greater than 100 pg/mL, you should seek medical attention, as it may indicate worsening heart failure.