What Does BNP Mean on a Blood Test?

What it means

BNP stands for B-type natriuretic peptide. The heart muscle, mostly in the lower pumping chambers, releases it when the heart is under strain and its walls are stretched by extra pressure or fluid. BNP helps the body get rid of salt and water and relaxes blood vessels. Many labs measure NT-proBNP instead, an inactive piece released at the same time.

Doctors order BNP or NT-proBNP when someone has breathlessness, tiredness or ankle swelling and they want to know whether heart failure might be the reason. A low result makes heart failure less likely. A raised result does not confirm it, but it tells the doctor that a heart scan, usually an echocardiogram, is worth doing. In people already known to have heart failure, the test can be repeated to see how things are changing.

BNP and NT-proBNP are not interchangeable numbers. They come from the same source but are measured on different scales, so your result can only be compared with the range printed for that exact test.

Where you may see it

• Blood tests from a GP or family doctor for breathlessness or swollen ankles
• Emergency department results for shortness of breath
• Heart failure clinic letters, often comparing the latest result with earlier ones
• Referral letters asking for an echocardiogram