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BNP (B-Type Natriuretic Peptide)

A hormone your heart releases when it is stretched. It helps clinicians judge whether symptoms like shortness of breath could be from heart failure.

AI-verified against cited sources. Awaiting expert reviewAlso called BNPLOINC 30934-4

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What it is

BNP (B-type natriuretic peptide) is a hormone made mostly in the heart's lower pumping chambers. The heart releases more of it when the walls are stretched by extra fluid or pressure. BNP tells your kidneys to get rid of salt and water and helps blood vessels relax, which eases the load on the heart. The test is mainly used when someone has symptoms such as shortness of breath or swelling. It works best as a rule-out test: a low result makes heart failure unlikely, while a higher one needs other tests to explain it.

Why it matters

In an emergency room study of 1,586 people with sudden shortness of breath, a BNP cutoff of 100 pg/mL was right 83.4% of the time in sorting heart failure from other causes, and a result under 50 pg/mL made heart failure very unlikely. BNP is not a diagnosis on its own. Many things other than heart failure change it, including age, sex, body weight, kidney function and heart rhythm, so it is read together with symptoms and tests such as an echocardiogram.

If it’s low

A low BNP makes heart failure unlikely as the cause of symptoms such as shortness of breath. Low results are also common in people with obesity or diabetes, where BNP can read lower than the true level of heart strain. If your symptoms continue, your clinician may still look for other causes.

Common causes

  • A heart that is not under extra strain
  • Obesity, where BNP tends to read lower
  • Diabetes, which is linked to lower natriuretic peptide levels
  • Younger age and male sex, when levels run lower on average

What can help

  • If symptoms persist, talk with your clinician even when your BNP is low

If it’s high

A higher BNP means the heart may be under strain. When you also have symptoms, that most often points toward heart failure, but BNP also rises with age, in women, and with several other conditions. In general, the higher the number, the more strain it reflects. Your clinician will read it together with your symptoms and other tests.

Common causes

  • Older age and female sex, when levels run higher on average
  • Chronic kidney disease or kidney failure
  • Atrial fibrillation or other abnormal heart rhythms
  • Heart valve disease or heart muscle disease
  • A blood clot in the lung or high blood pressure in the lungs
  • Severe infection, shock or a recent heart attack
  • Heart failure

What can help

  • Ask your clinician what is driving the result, since BNP alone cannot show the cause
  • Ask whether an echocardiogram or kidney tests would help
  • If you already have heart failure, follow the care plan from your clinician and tell them about new swelling, weight gain from fluid or shortness of breath

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: up to 100 pg/mL. Source: University of Washington Medicine, Department of Laboratory Medicine and Pathology, Cleveland Clinic, Pathology Tests Explained (Royal College of Pathologists of Australasia), New England Journal of Medicine, Journal of the American College of Cardiology, Circulation.

Pathology Tests Explained BNP decision cut-offs for people with symptoms (RCPA)

  • Under 100: heart failure unlikely as the cause of symptomsbelow 100 pg/mL
  • 100 to 500: unclear on its own, needs other tests100 to under 500 pg/mL
  • Above 500: heart failure considered likely500 and above pg/mL

2021 ESC heart failure BNP thresholds (non-acute 35 pg/mL, acute 100 pg/mL), as quoted in published papers

  • Under 35: below both thresholdsbelow 35 pg/mL
  • 35 to under 100: above the non-acute threshold, below the acute-setting threshold35 to under 100 pg/mL
  • 100 or higher: above both thresholds100 and above pg/mL

What can affect your result

  • Age: levels rise with age
  • Sex: levels are higher in women
  • Body weight: levels are lower with obesity
  • Kidney function, atrial fibrillation and lung conditions
  • Heart failure medicines that block neprilysin
  • Acute versus ongoing illness: thresholds differ by setting
  • Assay and sample type (EDTA plasma, bedside device or lab analyzer)
  • Obesity can lower BNP, so a low result may under-read heart strain. European heart failure experts suggest using cutoffs about 50% lower in people with obesity.
  • Older age, female sex, kidney disease, atrial fibrillation and some lung conditions can raise BNP without heart failure.
  • Sacubitril/valsartan, a heart failure medicine that blocks an enzyme (neprilysin) that breaks down BNP, can make BNP results behave unpredictably. NT-proBNP is often followed instead.
  • BNP breaks down quickly in a tube. Labs use EDTA plasma and separate it promptly; UW Medicine asks for centrifuging within 2 hours.
  • Assays differ, and bedside devices differ from lab analyzers, so compare results only with the same lab. BNP and NT-proBNP are not interchangeable.

BNP clears from the blood quickly (half-life about 20 minutes), so it can change within hours to days as heart strain changes.

When to talk to a clinician

Call 911 or your local emergency number for sudden or worsening shortness of breath, chest pain, fainting or confusion, whatever your BNP result is. Talk with your clinician soon if your BNP is above 500 pg/mL, or above 100 pg/mL with symptoms such as breathlessness, leg or belly swelling, or unusual tiredness. A low result does not rule out heart disease if your symptoms continue.

Questions you could ask

  • If I take a heart failure medicine, does that change whether you use BNP or NT-proBNP?
  • Which test and lab should I stick with so my results can be compared over time?
  • What do you think is behind my BNP, and which tests would help sort that out?
  • Would an echocardiogram or a kidney test be useful?
  • Should we recheck it, and when?
  • Given my symptoms and my weight, is a low BNP reassuring, or should we look further?

Questions people ask

What is the difference between BNP and NT-proBNP?

The heart releases both in equal amounts, but NT-proBNP stays in the blood longer and is more stable, so some labs prefer it. The numbers and cutoffs differ, so the two tests cannot be compared directly. Your lab uses one or the other.

Can I have a normal BNP and still have a heart problem?

Yes. BNP can read lower than expected if you carry extra weight, and some heart conditions raise it little or not at all. A normal result mainly makes heart failure unlikely as the cause of symptoms, so if you still have symptoms your clinician may suggest other tests.

How do I convert BNP between units?

pg/mL and ng/L are the same number, so 100 pg/mL is 100 ng/L. To convert pmol/L to pg/mL, multiply by 3.46. For example, 10 pmol/L is about 35 pg/mL. To go the other way, divide pg/mL by 3.46.

Show the science and sources

Units

  • 1 pg/mL = 1 pg/mL
  • 1 pg/mL = 1 ng/L
  • 1 pg/mL = 0.2887 pmol/L

Open the BNP unit converter

For clinicians and researchers

BNP is the 32-amino-acid active peptide released from ventricular myocardium together with NT-proBNP in a 1:1 ratio, in response to wall stretch from pressure or volume load. BNP has a half-life of about 20 minutes, versus 60-120 minutes for NT-proBNP, which is why NT-proBNP is preferred in some settings. Commercial BNP immunoassays can also detect proBNP, and neprilysin degrades mature BNP but not proBNP, which helps explain why measured BNP after sacubitril/valsartan changes inconsistently across studies. Reported decision points: 100 pg/mL in acute dyspnea (accuracy 83.4%, negative predictive value 96% below 50 pg/mL in the Breathing Not Properly study); the 2021 ESC guideline uses 35 pg/mL in non-acute and 100 pg/mL in acute presentations (as quoted in published papers); obese patients need cutoffs about 50% lower (Heart Failure Association of the ESC, 2019). In Framingham participants without heart failure, adjusted mean BNP in lean, overweight and obese men was 21.4, 15.5 and 12.7 pg/mL, and 21.1, 16.3 and 13.1 in women. In a healthy Olmsted County subset, BNP rose with age, was higher in women and varied by assay, which led to age-, sex- and assay-specific reference ranges. Reference intervals are not harmonized between labs or assays, and the PTEx cut-offs are described as international clinical decision cutoffs. Molecular weight 3464 g/mol gives 1 pmol/L = 3.464 pg/mL.

LOINC 30934-4 (primary), 42637-9, 47092-2. Specimen: plasma.

Sources

  1. B-Type Natriuretic Peptide (BNAP), UW Medicine Laboratory Test Guide, University of Washington Medicine, Department of Laboratory Medicine and Pathology
  2. B-Type Natriuretic Peptide (BNP) Test: Normal Levels & Purpose, Cleveland Clinic (2025)
  3. BNP and NT-proBNP tests, Pathology Tests Explained (Royal College of Pathologists of Australasia) (2026)
  4. Rapid measurement of B-type natriuretic peptide in the emergency diagnosis of heart failure, New England Journal of Medicine (2002)
  5. Plasma brain natriuretic peptide concentration: impact of age and gender, Journal of the American College of Cardiology (2002)
  6. Impact of obesity on plasma natriuretic peptide levels, Circulation (2004)
  7. Diagnostic Performance of Guideline-Recommended B-Type Natriuretic Peptide Thresholds for Detecting Elevated Left Ventricular End-Diastolic Pressure, Diagnostics (Basel) (2026)
  8. Guideline for the Use of Natriuretic Peptides in the Early Diagnosis and Management of Heart Failure in Primary Care (Eurasian Society of Heart Failure and Turkish Association of Family Medicine), Balkan Medical Journal (2025)
  9. Heart Failure Association of the European Society of Cardiology practical guidance on the use of natriuretic peptide concentrations, European Journal of Heart Failure (2019)
  10. Responses of B-type natriuretic peptide (BNP), mature BNP and proBNP to sacubitril/valsartan differs between responders and non-responders, Open Heart (2025)
  11. Nesiritide (PubChem CID 71308561), PubChem, National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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