What should you know about a BNP blood test?

BNP stands for B-type natriuretic peptide. The related NT-proBNP test measures a different fragment released at the same time. Both can help a clinician judge whether breathlessness, ankle swelling, unusual tiredness or other symptoms might be linked to pressure or stretching in the heart.

A raised result can signal strain on the heart, but it does not diagnose heart failure by itself. Levels can also be influenced by kidney problems, heart rhythm conditions, valve disease, age, body weight and some acute illnesses. A lower result can make heart failure less likely, although medicines and other factors may affect the reading.

Your clinician interprets the result using the laboratory's reference range, your symptoms, examination, medical history and often an electrocardiogram or echocardiogram. BNP and NT-proBNP are different tests, so their numbers should not be compared directly.

The sample is usually taken from a vein in your arm and sent to a laboratory. Ask whether you need to fast; preparation depends on the other blood tests ordered at the same visit. Tell the clinician about heart, kidney or liver conditions and provide a current list of prescription medicines, supplements and non-prescription medicines.

When the result is available, arrange a review rather than interpreting it in isolation. If it is raised, the next step may include heart imaging or specialist assessment. Continue prescribed treatment unless the clinician who manages it advises a change.

Seek emergency help for severe or rapidly worsening breathlessness, chest pain or pressure, fainting, sudden confusion, blue or grey lips, or coughing up pink frothy fluid. Do not wait for a BNP result when these symptoms are present.

Contact a healthcare professional promptly if breathlessness is new or worsening, swelling is increasing, you are waking repeatedly short of breath, or you have a sudden increase in weight with reduced urine. These symptoms need clinical assessment because several heart and non-heart conditions can cause them.

You could ask: Was my test BNP or NT-proBNP? What reference range does this laboratory use? How do my symptoms and kidney function affect the interpretation? Do I need an electrocardiogram, echocardiogram or another assessment? When should I seek help if my symptoms change?