BNP (B-type natriuretic peptide)
A hormone released by the heart muscle when it is stretched or under strain. It is used mainly to help diagnose and monitor heart failure: a low level makes heart failure unlikely, while a high level supports it and tends to track how severe the strain is.
What it measures
BNP (B-type natriuretic peptide) is a hormone made and released by the heart's muscle cells, particularly in the ventricles, when they are stretched by increased pressure or volume — in other words, when the heart is under strain. Its natural job is to help the body offload fluid and lower blood pressure. Because it rises in proportion to how hard the heart is working against a load, measuring it is one of the most useful blood tests for heart failure. Its main use is in someone who is breathless: a low BNP makes heart failure an unlikely cause of the breathlessness, helpfully pointing elsewhere (such as the lungs), while a raised level supports heart failure and, broadly, the higher it is the more severe the strain. It is also used to monitor known heart failure over time and to help judge prognosis. A closely related test, NT-proBNP, is a more stable fragment released in the same process and is used in the same way. Levels rise naturally with age and with reduced kidney function, and can rise in other cardiac stresses, so results are interpreted with the clinical picture rather than as a single number.
What a high value can mean
- Heart failure — the main use; a raised level supports it and broadly tracks severity.
- Other causes of heart strain — a heart attack, an irregular rhythm such as atrial fibrillation, valve disease, or a blood clot in the lung.
- Reduced kidney function — raises it independently, so it is read with kidney function.
- Older age — levels rise naturally with age.
What a low value can mean
- A low level makes heart failure unlikely — its most valuable use in a breathless person, pointing toward a non-cardiac cause.
- Well-treated heart failure — a falling level can reflect effective treatment.
When to discuss with a doctor
BNP is most useful when someone is breathless and the question is whether the heart is the cause: a low level makes heart failure unlikely and helps look elsewhere, while a raised level supports it and prompts a heart assessment (usually including an echocardiogram). In someone with known heart failure, it is used to help monitor the condition and guide care. Because age and kidney function raise it independently, and other cardiac problems can too, the number is always interpreted alongside symptoms and the rest of the picture rather than alone. New or worsening breathlessness, swelling of the legs, or waking at night short of breath should be assessed by a doctor. Mediora.AI can surface a raised BNP or NT-proBNP alongside kidney function and other cardiac markers so the heart-strain pattern is visible; the diagnosis and treatment of heart failure belong with your doctor.