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A BNP blood test measures B-type natriuretic peptide, a protein-like hormone released by the heart when the heart muscle is under pressure or stretch. Clinicians most often use BNP, or the related NT-proBNP test, to help evaluate symptoms that could be caused by heart failure, especially shortness of breath, leg swelling, fatigue, or trouble lying flat.
Get urgent medical help now if you have severe shortness of breath, chest pain, fainting, blue lips or fingers, confusion, or sudden worsening swelling. A BNP result is not a substitute for emergency evaluation when symptoms are serious.
Quick take
- What it measures: BNP, a natriuretic peptide released when the heart is working harder than usual.
- Main use: Helping confirm or rule out heart failure in people with symptoms, and sometimes monitoring known heart failure.
- Sample: Blood from a vein; some hospital settings may use faster point-of-care testing.
- Fasting: Usually not required.
- Common reference point: BNP below 100 pg/mL often makes heart failure less likely in a symptomatic person, but labs and clinical settings vary.
- Important limitation: A high BNP is not a diagnosis by itself. Kidney disease, lung conditions, severe infection, pulmonary embolism, age, body size, and other factors can affect results.
What does a BNP blood test measure?
BNP stands for B-type natriuretic peptide. Your heart releases BNP when its chambers are stretched, often because pressure or fluid volume is higher than usual. BNP helps the body reduce strain on the heart by promoting salt and water excretion and widening blood vessels. MedlinePlus describes BNP and NT-proBNP tests as blood tests mainly used to help confirm or rule out heart failure in people who have symptoms. MedlinePlus
The test is most useful when the clinical question is specific: Are symptoms such as shortness of breath likely to be from heart failure, or should another cause be considered? The 2022 AHA/ACC/HFSA heart failure guideline states that measuring BNP or NT-proBNP is useful in patients presenting with dyspnea to support a diagnosis or exclusion of heart failure. AHA/ACC/HFSA guideline
Why a clinician may order BNP
A BNP blood test may be ordered when symptoms suggest possible heart failure, when a clinician needs help distinguishing heart-related shortness of breath from lung, kidney, liver, anemia, or other causes, or when someone with known heart failure has worsening symptoms. The American Heart Association lists natriuretic peptides, including BNP and NT-proBNP, among blood biomarkers used in heart failure evaluation, alongside tests such as electrolytes, albumin, creatinine, chest X-ray, EKG, and echocardiogram. American Heart Association
| Situation | How BNP can help | What usually happens next |
|---|---|---|
| New shortness of breath | A low BNP can make heart failure less likely; a high BNP can support further cardiac evaluation. | Exam, oxygen level, EKG, chest imaging, kidney tests, and often echocardiography. |
| Leg, ankle, or abdominal swelling | May show whether the heart is under strain, especially when swelling occurs with breathlessness or fatigue. | Evaluation for heart, kidney, liver, vein, medication, and fluid-balance causes. |
| Known heart failure with worsening symptoms | May help assess whether cardiac strain has increased. | Medication review, weight/fluid assessment, kidney and electrolyte tests, and follow-up care plan. |
| Monitoring after treatment changes | Trends may provide context, but serial BNP testing is not interpreted in isolation. | Clinician compares symptoms, exam, kidney function, and imaging or other tests as needed. |
How to prepare for a BNP blood test
Most people do not need to fast before BNP or NT-proBNP testing. MedlinePlus states that no special preparations are needed for natriuretic peptide tests. MedlinePlus
Before the blood draw, tell the ordering clinician or testing service about prescription medicines, over-the-counter medicines, supplements, pregnancy status, kidney disease, and known heart or lung conditions. Do not stop heart, blood pressure, diuretic, or other prescribed medicines unless the clinician who prescribed them tells you to.
Biotin note: High-dose biotin supplements can interfere with some lab tests. The FDA has warned that biotin may cause incorrect results in certain tests, and some BNP testing providers advise stopping biotin for a period before collection. Ask the ordering clinician or lab what applies to your specific assay and supplement dose. FDA
How to read BNP blood test results
BNP results are commonly reported in picograms per milliliter (pg/mL). A widely used general reference point is that BNP below 100 pg/mL makes heart failure less likely in a symptomatic person, while a result above 100 pg/mL is considered elevated and needs clinical interpretation. MedlinePlus notes that normal value ranges may vary slightly among laboratories and that clinicians should interpret results with symptoms, history, and other test findings. MedlinePlus Medical Encyclopedia
| BNP result pattern | General meaning | Important cautions |
|---|---|---|
| Below 100 pg/mL | Heart failure is less likely as the cause of symptoms in many settings. | Obesity can lower BNP, and no single result rules out every heart condition. |
| 100 pg/mL or higher | BNP is elevated and may support concern for heart failure or heart strain. | Other conditions can raise BNP; more evaluation is usually needed. |
| Markedly elevated | Higher values often suggest greater cardiac stress or more severe illness. | Severity cannot be judged from BNP alone; kidney function, age, symptoms, and imaging matter. |
Conditions other than heart failure can raise BNP or NT-proBNP. MedlinePlus lists kidney failure, other types of heart disease, pulmonary embolism, pulmonary hypertension, severe infection, and lung problems as possible causes of high BNP. MedlinePlus Medical Encyclopedia
Why symptoms matter
BNP is most meaningful when matched to the reason it was ordered. Shortness of breath while lying flat, unusual fatigue, swelling in the ankles, feet, legs, abdomen, or neck veins, and rapid weight gain can occur in heart failure, according to the National Heart, Lung, and Blood Institute. NHLBI
Why BNP is not a stand-alone diagnosis
A clinician may use BNP as one part of a workup. An echocardiogram, for example, uses sound waves to show the heart’s structure and pumping function and can help evaluate heart failure and valve problems. American Heart Association
BNP vs. NT-proBNP: what is the difference?
BNP and NT-proBNP are related markers released during the same biological process, but they are not numerically interchangeable. The AHA/ACC/HFSA guideline notes that either BNP or NT-proBNP may be used in patient care settings, but their absolute values and cut points should not be used interchangeably. AHA/ACC/HFSA guideline
| Feature | BNP | NT-proBNP |
|---|---|---|
| What it reflects | Heart wall stretch and cardiac strain | Heart wall stretch and cardiac strain |
| Common use | Diagnosis support, exclusion support, risk context, sometimes monitoring | Similar clinical uses |
| Numeric cutoffs | Often lower numbers; BNP below 100 pg/mL is a common rule-out reference point | Different cutoffs; values are often higher and age-sensitive |
| Can results be compared directly? | No. Do not convert or compare BNP and NT-proBNP as if they were the same test. | |
What can affect BNP results?
Several factors can make BNP higher or lower than expected. Higher values may occur with heart failure, kidney dysfunction, pulmonary hypertension, pulmonary embolism, severe infection, acute coronary syndromes, and some structural heart conditions. Lower-than-expected natriuretic peptide levels can occur in people with obesity, which may reduce diagnostic sensitivity. The heart failure guideline specifically notes that obesity is associated with lower BNP and NT-proBNP levels. AHA/ACC/HFSA guideline
Age also matters: BNP and NT-proBNP levels tend to rise with age, and kidney function can strongly influence natriuretic peptide concentrations. That is why your report’s reference interval and your clinical context matter more than a single internet cutoff.
Can you order a BNP blood test yourself?
BNP is available through some direct-to-consumer lab services, usually as an in-person blood draw rather than a home finger-prick test. Because BNP is often ordered for symptoms that can be urgent, self-ordering is best viewed as a convenience for planned evaluation or follow-up—not as a way to manage severe or rapidly worsening symptoms without medical care.
When comparing self-pay options, look at the effective total cost: the listed test price plus any provider-charged physician/order fee, lab processing fee, draw fee, or required service fee. Also compare collection locations, state restrictions, turnaround time, whether the order is reviewed by a licensed clinician, and whether abnormal results trigger follow-up instructions.
| Provider example | Listed BNP test price shown on provider page | Provider fee noted on provider page | Effective cost to the patient from shown information | Collection / ordering notes |
|---|---|---|---|---|
| HealthLabs | $99 | No additional mandatory fee shown in the cited page content | $99 before optional add-ons or changes at checkout | Provider page describes online ordering, local lab collection, and most results in 1–3 business days. |
| Walk-In Lab | $109 | $6 physician fee charged by Walk-In Lab’s ordering workflow | $115 before optional add-ons or promotions | Provider page lists no fasting and typical 1–2 day results, with a biotin hold instruction. |
| Request A Test | $129 for one listed lab option | No additional mandatory fee shown in the cited page content | $129 for the listed option before optional add-ons or changes at checkout | Provider page lists blood specimen collection and typical 2 business day results for one lab option. |
| Private MD Labs | $148 | Provider page states prescription and lab fees are included | $148 before optional add-ons or promotions | Provider page describes doctor order creation, lab collection, and 4,000 nearby lab locations. |
These examples are not a ranking. Prices, promotions, available labs, and state access can change at checkout. If you are comparing options for planned testing, review the final cart total and collection instructions before paying. You can also use CTX Stat’s tool when you want a side-by-side view of lab ordering options.
What to ask after you get your BNP result
- Is this BNP result interpreted using my lab’s reference range?
- Was BNP or NT-proBNP measured, and are we comparing the same test as before?
- Could kidney function, body weight, age, infection, lung disease, or medicines be affecting the result?
- Do I need an echocardiogram, EKG, chest imaging, kidney tests, or follow-up with cardiology?
- If I already have heart failure, does this result change my treatment plan or follow-up timing?
FAQs about the BNP blood test
What does a BNP blood test measure?
It measures B-type natriuretic peptide, a substance released by the heart when the heart muscle is stretched or under strain. It is mainly used to help evaluate possible heart failure in people with symptoms.
Do I need to fast before a BNP blood test?
Usually no. BNP and NT-proBNP testing generally does not require fasting. Follow any instructions from the ordering clinician or lab, especially if you take high-dose biotin supplements.
What is a normal BNP level?
A BNP below 100 pg/mL is commonly used as a level that makes heart failure less likely in many symptomatic adults. However, reference ranges vary, and some people need more evaluation even with a lower result.
What does a high BNP result mean?
A high BNP means the heart may be under strain, and heart failure is one possible cause. It can also be elevated with kidney failure, pulmonary embolism, pulmonary hypertension, severe infection, and other heart or lung conditions.
Can obesity affect BNP?
Yes. Obesity is associated with lower BNP and NT-proBNP levels, which can make interpretation more difficult. Clinicians may continue evaluating for heart failure if symptoms and exam findings are concerning.
Is BNP the same as NT-proBNP?
No. They are related natriuretic peptide tests used for similar purposes, but the numbers and cutoffs are different. Do not compare a BNP result with an NT-proBNP result as if they were the same measurement.
How quickly are BNP results available?
In hospitals, BNP can sometimes be available rapidly because it is often used in urgent shortness-of-breath evaluations. Outpatient direct-order providers commonly list turnaround times of about 1–3 business days, but timing depends on the lab and collection logistics.
Should I order BNP if I feel short of breath?
If shortness of breath is severe, sudden, worsening, or accompanied by chest pain, fainting, confusion, blue lips, or severe weakness, seek urgent care rather than waiting for an outpatient lab result. For non-urgent or follow-up situations, a clinician can help decide whether BNP, NT-proBNP, or other testing is appropriate.
Sources
- MedlinePlus: Natriuretic Peptide Tests (BNP, NT-proBNP)
- MedlinePlus Medical Encyclopedia: Brain natriuretic peptide test
- 2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure
- American Heart Association: Diagnosing Heart Failure
- NHLBI: Heart Failure Symptoms
- FDA: Testing for Biotin Interference in In Vitro Diagnostic Devices
