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NT-proBNP (N-Terminal pro-B-Type Natriuretic Peptide)

A protein fragment your heart releases when it is under strain. It helps clinicians judge whether symptoms like breathlessness could come from heart failure.

AI-verified against cited sources. Awaiting expert reviewAlso called NT-proBNP, NTproBNP, NT-BNPLOINC 33762-6

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What it is

NT-proBNP is made when the lower chambers of your heart are stretched by extra fluid or pressure. The heart releases it in equal amounts with BNP, a hormone that helps your body get rid of salt and water. NT-proBNP itself is inactive, but it stays in the blood longer than BNP, so many labs measure it. The test is mostly 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 result needs other tests to explain it.

Why it matters

A low NT-proBNP makes heart failure unlikely as the cause of symptoms, which can spare people more testing. A higher result is a signal to look more closely, often with an echocardiogram (a heart ultrasound). Many things other than heart failure change it, including age, sex, weight, kidney function and heart rhythm, so it is read together with symptoms and other tests. For people who already have heart failure, a falling level over time has been linked to better outcomes and a rising level to a worsening course.

If it’s low

A low NT-proBNP makes heart failure unlikely as the cause of symptoms such as shortness of breath. Carrying extra weight can lower the number, so a low result may under-read heart strain in people with obesity. If your symptoms continue, your clinician may still look for other causes.

Common causes

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

What can help

  • If symptoms continue, talk with your clinician even when your result is low

If it’s high

A higher NT-proBNP means the heart may be under strain. When you also have symptoms, it can be a sign of heart failure, but the number also rises with age, in women, and with kidney disease or an irregular heart rhythm. 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, since levels rise with age even in healthy people
  • Female sex, when levels run higher on average
  • Chronic kidney disease, because the kidneys help clear NT-proBNP
  • Atrial fibrillation or other heart rhythm problems
  • Heart valve disease or heart muscle disease
  • A blood clot in the lung or high blood pressure in the lungs
  • Heart failure

What can help

  • Ask your clinician what is behind the result, since NT-proBNP alone cannot show the cause
  • Ask whether an echocardiogram or kidney tests would help
  • If you already have heart failure, follow your care plan and tell your clinician about new swelling, fast weight gain from fluid or worse breathlessness

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.

The usual range depends on age. Choose an age to see the one that applies.

See NT-proBNP by age and sex, with the U.S. survey numbers where they exist.

ESC/AHA outpatient (non-acute) rule-out threshold for heart failure, as quoted in published papers

  • Under 125: below the usual outpatient rule-out cutoff for heart failurebelow 125 pg/mL
  • 125 or higher: at or above the outpatient cutoff, usually looked into with other tests125 and above pg/mL

ICON-RELOADED emergency-department cutoffs for acute heart failure, ages under 50

  • Under 300: below the emergency-department rule-out cutoff for acute heart failurebelow 300 pg/mL
  • 300 to under 450: between the rule-out cutoff and the age-based cutoff (grey zone)300 to under 450 pg/mL
  • 450 or higher: at or above the age-based emergency-department cutoff for acute heart failure450 and above pg/mL

ICON-RELOADED emergency-department cutoffs for acute heart failure, ages 50 to 74

  • Under 300: below the emergency-department rule-out cutoff for acute heart failurebelow 300 pg/mL
  • 300 to under 900: between the rule-out cutoff and the age-based cutoff (grey zone)300 to under 900 pg/mL
  • 900 or higher: at or above the age-based emergency-department cutoff for acute heart failure900 and above pg/mL

ICON-RELOADED emergency-department cutoffs for acute heart failure, ages 75 and older

  • Under 300: below the emergency-department rule-out cutoff for acute heart failurebelow 300 pg/mL
  • 300 to under 1,800: between the rule-out cutoff and the age-based cutoff (grey zone)300 to under 1,800 pg/mL
  • 1,800 or higher: at or above the age-based emergency-department cutoff for acute heart failure1,800 and above pg/mL

UK NICE (NG106) referral thresholds, as quoted in a 2025 consensus report (ng/L equals pg/mL)

  • Under 400: heart failure less likely, consider other causesbelow 400 pg/mL
  • 400 to 2,000 (inclusive): specialist assessment and echocardiogram within 6 weeks400 to under 2,000 pg/mL
  • Above 2,000: specialist assessment and echocardiogram within 2 weeks2,000 and above pg/mL

What can affect your result

  • Age: levels rise with age, and healthy adults over 70 often sit above the outpatient cutoff of 125 pg/mL
  • Sex: levels are higher in women, although guidelines do not set separate cutoffs
  • Body weight: levels are lower with obesity
  • Kidney function, atrial fibrillation and lung conditions
  • Setting: cutoffs differ between a hospital emergency visit and outpatient testing
  • Assay and lab: results from different assays are not interchangeable
  • Heart failure medicines such as sacubitril/valsartan do not distort NT-proBNP the way they can distort BNP
  • Obesity lowers NT-proBNP, so a low result can under-read heart strain. European heart failure experts suggest cutoffs about 50% lower in people with obesity.
  • Older age, female sex, kidney disease and atrial fibrillation raise NT-proBNP without heart failure. Kidney disease matters more for NT-proBNP than for BNP because the kidneys help clear it.
  • Sacubitril/valsartan, a heart failure medicine, does not raise NT-proBNP the way it can affect BNP, which is one reason clinicians often follow NT-proBNP in people taking it.
  • Assays differ. In one comparison the Roche assay read about 9% to 25% lower than the Abbott assay, so compare results only from the same lab and assay.
  • Very high-dose biotin supplements can make some immunoassays read falsely low, and tolerance differs between assays, so tell the lab if you take biotin.

NT-proBNP has a half-life of about 1 to 2 hours, so it can change within days as fluid load and heart strain change.

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 result is. Talk with your clinician soon if your result is above your lab's range and you have breathlessness, leg or belly swelling or unusual tiredness. In UK guidance, a level above 2,000 ng/L leads to a specialist referral within 2 weeks, and 400 to 2,000 ng/L within 6 weeks. A low result does not rule out heart disease if your symptoms continue.

Questions you could ask

  • Which cutoff does my lab use, and does it apply to my age and situation?
  • What do you think is driving my result: my heart, my kidneys, my heart rhythm or my age?
  • Would an echocardiogram or other tests help?
  • Should we recheck this, and which assay and lab should I use so the results can be compared?
  • Could my weight make this result read lower than my heart strain?
  • If my symptoms continue, what else should we look into?

Questions people ask

What is the difference between NT-proBNP and BNP?

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.

Why is my NT-proBNP flagged high when I feel fine?

NT-proBNP rises with age, is higher in women, and goes up with kidney disease or an irregular heart rhythm such as atrial fibrillation. In one large study, roughly half or more of healthy people aged 70 and older were above the standard outpatient cutoff of 125 pg/mL. A flag is a reason to talk with your clinician, not a diagnosis.

How do I convert NT-proBNP between units?

pg/mL and ng/L are the same number, so 125 pg/mL is 125 ng/L. To convert pmol/L to pg/mL, multiply by 8.457, so 125 pg/mL is about 14.8 pmol/L. To go the other way, divide by 8.457.

Show the science and sources

Units

  • 1 pg/mL = 1 pg/mL
  • 1 pg/mL = 1 ng/L
  • 1 pg/mL = 0.1182 pmol/L

Open the NT-proBNP unit converter

Is a change real?

NT-proBNP naturally varies about 34.3% from test to test in the same healthy person. Between two results from the same lab, a rise of 182% or more, or a fall of 65% or more, is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Biological Variation of Natriuretic Peptides and Other Cardiovascular Disease-Related Biomarkers: A Systematic Review and Meta-analysis (Fernandez-Calle P et al.).

For clinicians and researchers

NT-proBNP is the inactive 76-amino-acid N-terminal fragment cleaved from proBNP, released from ventricular myocardium with active BNP in a 1:1 ratio in response to wall stretch from pressure or volume load. It has a longer half-life than BNP (60 to 120 minutes versus about 20 minutes), is more dependent on renal clearance, and is not a neprilysin substrate, so levels do not rise on sacubitril/valsartan as BNP can. Decision points: ESC and AHA recommend 125 pg/mL to rule out chronic heart failure in non-acute settings, and the ESC uses 300 pg/mL in acute dyspnea. For acute heart failure, ICON-RELOADED (1,461 emergency patients, 19% with acute heart failure) found age-stratified cutoffs of 450, 900 and 1,800 pg/mL had positive predictive values of 53.6%, 58.4% and 62.0%, while a rule-out cutoff of 300 pg/mL had sensitivity 93.9% and negative predictive value 98.0%. NICE uses 400 and 2,000 ng/L for referral timing. Obese patients need cutoffs about 50% lower (HFA 2019). In the AugUR population study, 49% to 69% of cardiovascular-healthy adults aged 70 and older (depending on age group and how strictly healthy was defined) exceeded 125 pg/mL, and 97.5th percentiles were roughly 540 to 940 pg/mL, so the single outpatient cutoff has low specificity in older age. Assays are not harmonized: Roche read about 9% to 25% lower than Abbott in one comparison, with the gap largest at low concentrations. Molecular weight (average mass of residues 27 to 102 of UniProt P16860) is about 8,457 g/mol, so 1 pmol/L = 8.457 pg/mL.

LOINC 33762-6 (primary), 83107-3, 33763-4, 83108-1. Specimen: serum-or-plasma.

Sources

  1. B-Type Natriuretic Peptide (BNP) Test, Cleveland Clinic
  2. NT-ProBNP (test NTBPRD), UW Medicine Laboratory Test Guide, UW Medicine Laboratory Medicine
  3. N-Terminal Pro-B-Type Natriuretic Peptide in the Emergency Department: The ICON-RELOADED Study, Journal of the American College of Cardiology (2018)
  4. Guideline for the Use of Natriuretic Peptides in the Early Diagnosis and Management of Heart Failure in Primary Care (Joint Consensus Report by the Eurasian Society of Heart Failure and the Turkish Association of Family Medicine), Balkan Medical Journal (2025)
  5. NT-proBNP in the very old population: reference values and heart failure specificity from the AugUR-study, Clinical Research in Cardiology (2026)
  6. Heart Failure Association of the European Society of Cardiology practical guidance on the use of natriuretic peptide concentrations, European Journal of Heart Failure (2019)
  7. Performance of the Abbott Architect Immuno-Chemiluminometric NT-proBNP Assay, Diagnostics (2022)
  8. Cardiac biomarkers response under angiotensin receptor-neprilysin inhibitor: a sub-analysis of the NATRIUM-HF study, ESC Heart Failure (2026)
  9. NPPB, Natriuretic peptides B, Homo sapiens (P16860), UniProt

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

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