What are BNP and NT-proBNP?
B-type natriuretic peptide (BNP) and its inactive fragment NT-proBNP are hormones released by the ventricular walls of the heart when they are stretched or under increased pressure — as happens in heart failure, when the heart cannot pump blood efficiently and fluid backs up. Both tests indicate the same process; different labs use different assays. They are the most important blood tests for: diagnosing heart failure in a patient with shortness of breath, assessing severity, monitoring treatment response, and predicting prognosis.
Normal range and interpretation
| Test | Normal | Grey Zone | Heart Failure Likely |
|---|---|---|---|
| BNP | < 100 pg/mL | 100 – 400 pg/mL | > 400 pg/mL |
| NT-proBNP (<75 yrs) | < 125 pg/mL | 125 – 900 pg/mL | > 900 pg/mL |
| NT-proBNP (≥75 yrs) | < 125 pg/mL | — | > 1,800 pg/mL |
HIGH BNP / NT-proBNP — Heart Failure or Cardiac Stress
Very high BNP or NT-proBNP strongly indicates heart failure. In patients with shortness of breath, a high BNP is more than 90% accurate at confirming a cardiac cause. Very high values (>1,000 pg/mL BNP or >5,000 pg/mL NT-proBNP) indicate severe heart failure and poor short-term prognosis without treatment. BNP/NT-proBNP also rises in: acute coronary syndrome, pulmonary embolism, atrial fibrillation, severe kidney disease (reduced clearance) and critical illness.
LOW / NORMAL BNP / NT-proBNP — Heart Failure Unlikely
A normal BNP or NT-proBNP in a patient with shortness of breath is very reassuring that heart failure is NOT the cause. The negative predictive value exceeds 95%. This helps redirect investigation toward lung causes (asthma, COPD, pneumonia, pulmonary embolism) or non-cardiac causes.
Using BNP to monitor heart failure treatment
In a patient already diagnosed with heart failure, serial BNP or NT-proBNP measurements track response to treatment. A falling BNP as medications (ACE inhibitors, ARBs, beta-blockers, diuretics, SGLT2 inhibitors) are optimised indicates improving cardiac function. A rising BNP during apparent stability warns of decompensation before hospitalisation becomes necessary.
Questions to ask your doctor
- Is my shortness of breath from my heart or my lungs?
- What is my BNP trend over time?
- Do I need an echocardiogram?
- How well is my heart failure treatment working?
- What medications protect my heart and reduce my BNP?