B-Type Natriuretic Peptide (BNP) Test: Normal, High, and Levels

B-Type Natriuretic Peptide (BNP) Test

BNP blood test overview

If your doctor orders a BNP test, you are probably showing symptoms of heart failure. The test measures a hormone called “brain natriuretic peptide” (BNP), which is released by the heart when it is under strain. BNP levels serve as an important marker for heart failure, helping doctors diagnose the condition and assess its severity.

During heart failure, pressure builds up in the chambers of your heart and creates BNP. When the heart works harder and doesn’t pump blood well, it releases this hormone in large amounts. BNP widens your blood vessels to help improve circulation. BNP levels rise in direct proportion to the severity of heart failure, and that’s why higher BNP levels are often an indicator of worsening heart function.

Most emergency departments can get your BNP test results in about 15 minutes. This rapid result allows for faster decision-making, particularly in cases where heart failure or other serious cardiac conditions are suspected.

Here is information you can use to get a clearer understanding of heart failure and the value of this test. It will help you understand what the results mean and how you can use them to help improve your health. Regular testing and close monitoring of BNP levels are essential to managing heart failure effectively, and this helps health care providers make timely adjustments and prevent complications.

What is the purpose of the BNP blood test?

When you have symptoms of heart failure, such as fatigue and shortness of breath, a BNP test can help your doctor determine whether it’s heart failure or pneumonia. The BNP test is particularly useful in distinguishing heart failure from other potential causes of these symptoms. BNP blood tests lead to an accurate diagnosis of heart failure about 90% of the time, making it a critical tool in the diagnostic process. BNP levels can also help your doctor determine your outlook after heart failure. Generally, a higher level means a worse outcome. As BNP levels drop, however, you’ll start to feel better and breathe easier, and your outlook will get better, too. This improvement in BNP levels correlates with a better prognosis, as the heart begins to stabilize and recover. After diagnosis, additional BNP tests can:

• Show how well your treatment is working
• Let doctors know when it is safe for you to leave the hospital

Doctors will continue to monitor BNP levels over time to track your progress and adjust your treatment plan as necessary. For example, if BNP levels remain elevated despite treatment, this may indicate that the heart health is not improving or that additional interventions are needed. On the other hand, a significant drop in BNP levels may signal that the heart is recovering and that a less aggressive treatment approach can be considered.

Preparing for the BNP lab test

You don’t need to fast or do anything to prepare for the test. You can get it at any time of day, as BNP levels are not significantly affected by the timing of the test.

Make sure your doctor knows about all the medications, vitamins, herbs, and supplements you take. That includes ones that don’t need a prescription. These can affect how your doctor interprets your BNP readings. Some medications, such as ACE inhibitors, diuretics, or beta-blockers, can affect BNP levels by either raising or lowering them, depending on their effect on the heart and fluid balance.

It is also helpful to notify your doctor if you have any existing medical conditions, such as kidney disease, liver disease, or thyroid disorders, as these can also affect BNP test results. BNP levels can be elevated in conditions that place stress on the heart, such as heart failure or kidney problems. Understanding your complete health history is key to evaluating the results.

What are normal and high BNP levels?

BNP tests, also called a B-type natriuretic peptide test, measure BNP by picograms (pg) per milliliter (mL) or nanograms per liter. The range includes:

• Normal: Less than 100 pg/mL
• High: More than 400 pg/mL
• Between 100 and 400 pg/mL requires a doctor’s evaluation, as this range can be indicative of a range of conditions, including heart failure, but could also be caused by other health issues.

Another test that measures BNP, called the NT-proBNP, has these ranges that vary by age:

Condition Ages BNP Level (pg/mL) Normal Any Less than 300 Possible heart failure Under the age of 50 More than 450 Possible heart failure Between ages 50 and 75 More than 900 Possible heart failure Over the age of 75 More than 1,800

It’s important to note that BNP tests results can also vary by sex, body mass index, health history, and other factors. Levels tend to get higher as you age. BNP is also usually higher in women than men. People who are obese tend to have lower levels.

Elevated BNP levels can result from conditions such as kidney disease, liver disease, and pulmonary disorders, which may require additional diagnostic tests to identify the underlying cause. As such, it is important to interpret BNP levels in conjunction with other diagnostic information and under the guidance of a health care professional. Ask your doctor what your specific results mean for you, as they will consider all factors, including your age, sex, weight, and overall health, to help determine the most accurate diagnosis and treatment plan for your condition.

What do high or low BNP levels mean?

Low BNP levels mean you likely don’t have heart failure. Your doctor can rule that diagnosis out and look at other reasons why you may have symptoms such as shortness of breath. Low BNP levels help exclude heart failure, as low levels typically indicate that the heart is not under significant stress. This can help narrow down the causes of your symptoms, guiding your health care provider toward the correct diagnosis. High BNP levels mean that your doctor may make a diagnosis of heart failure. Also, levels are higher when heart failure is worse, and they go down when the heart is stable. Monitoring BNP levels over time can provide valuable insights into how well the heart is responding to therapy. If you have high BNP levels but the doctor rules out heart failure, the levels may point to other conditions such as:

• Kidney failure or dialysis use
• Severe lung disease
• Pneumonia
• COPD (chronic obstructive pulmonary disease)
• Coronary artery disease
• Afib (atrial fibrillation)
• Pre-existing heart failure
• Nesiritide use, a synthetic form of BNP used to treat heart failure

By monitoring BNP levels, doctors can assess the severity of heart failure or other related conditions, track treatment progress, and guide clinical decisions. Elevated BNP levels can be indicative of a wide range of issues, so accompanying tests are crucial in making an accurate diagnosis.

How to bring BNP levels back to normal

When BNP levels are above the normal range, doctors usually lower them with medication. Your doctor may prescribe ACE inhibitors, beta-blockers, or diuretics to help. Achieving and maintaining a BNP normal range is often important for managing heart failure and other cardiovascular conditions. Regular monitoring of BNP levels can help track progress and ensure optimal heart function over time.

Other factors that you may or may not be able to control could also keep BNP levels up, such as:

• High blood pressure
• An overactive thyroid
• High levels of the stress hormone cortisol
• Certain rare tumors
• Brain hemorrhages
• A liver disease called cirrhosis
• A severe inflammatory reaction to an infection called sepsis
• Chemotherapy

Conditions that can lower BNP levels include:

• Obesity
• A quick buildup of fluid in the lungs called flash pulmonary edema
• A rare form of heart failure called pericardial constriction

Other tests for heart failure

The BNP test is only one way to monitor heart failure. It measures BNP (B-type natriuretic peptide), a hormone produced by the heart in response to increased stress. Another blood test, called ANP, measures atrial natriuretic peptide, which is a hormone-like BNP. The larger, more powerful chambers in the lower portion of your heart produce BNP. The upper chambers produce ANP. Both BNP and ANP are involved in regulating blood pressure, fluid balance, and heart function, with their levels rising in response to heart strain or dysfunction. These peptides help the body counteract the effects of fluid retention and excessive blood pressure, making them valuable indicators of stress on the heart.

Doctors may confirm your results with other blood tests, a chest X-ray, an electrocardiogram, or an echocardiogram. These tests can provide more details about the condition of your heart. By combining the BNP test with imaging and other diagnostic tools, doctors can obtain a clearer picture of your heart’s health and take appropriate action to manage heart failure.

Frequently asked questions

• How can I lower my BNP levels? To lower BNP levels, it is crucial to address the underlying causes, such as heart failure, and improve cardiac function through prescribed medications like ACE inhibitors, beta-blockers, and diuretics. Controlling other risk factors, such as hypertension and diabetes, is also important. Adopting a heart-healthy diet, engaging in regular physical activity, managing stress, and limiting alcohol intake can contribute to lowering BNP levels and improving overall heart health.
• What is the significance of low BNP levels? Low BNP levels typically indicate that heart failure or significant cardiac dysfunction is unlikely, as BNP is released in response to cardiac stress. However, factors such as obesity, age, and certain medications can also reduce BNP levels, so low levels do not exclude other potential conditions. BNP levels should always be interpreted in conjunction with other clinical findings and diagnostic information.
• How often should BNP levels be monitored? BNP levels are typically monitored every few months in stable patients with heart failure or other cardiovascular conditions; the frequency may increase if the patient experiences changes in symptoms or treatment. For individuals with acute heart failure or those adjusting medications, more frequent monitoring may be necessary to assess therapeutic response and guide clinical decisions. Regular follow-up with a health care provider is essential for proper management.
• Can medications affect BNP levels? Yes, medications can affect BNP levels. Drugs that reduce the heart’s workload, such as ACE inhibitors, beta-blockers, and diuretics, often lower BNP levels by improving heart function. On the other hand, medications that increase heart strain, like those causing fluid retention, high blood pressure, certain corticosteroids, NSAIDs, and some antihypertensives, can raise BNP levels. Angiotensin receptor blockers (ARBs) can also elevate BNP levels, so it is important to interpret BNP results within the context of the patient’s treatment regimen.
• What other conditions can cause elevated BNP levels? Elevated BNP levels can be seen in conditions other than heart failure, such as chronic obstructive pulmonary disease (COPD), acute myocardial infarction, acute kidney injury, chronic kidney disease, sepsis, and pulmonary embolism. Additionally, conditions such as severe hypertension, liver cirrhosis, and acute respiratory distress syndrome (ARDS) may also cause increased BNP levels due to increased cardiac stress or other underlying mechanisms.
• What does a BNP test measure and how is it performed? A BNP test measures the level of brain natriuretic peptide (BNP) in the blood, a hormone released by the heart in response to increased pressure and strain, often due to heart failure. The test is typically performed by drawing a blood sample from a vein, usually in the arm, and the results are used to assess heart function, help diagnose conditions such as heart failure, and guide treatment decisions.
• What is considered a normal BNP range for adults? The normal BNP level for adults is typically less than 100 pg/mL, although this can vary slightly depending on the laboratory and specific testing methods used. Higher levels may indicate heart failure or other cardiac conditions, with levels greater than 400 pg/mL often suggesting acute heart failure. It is important to consider other clinical symptoms and diagnostic tests when interpreting BNP levels.
• How do BNP test results help diagnose heart conditions? BNP test results help diagnose heart conditions by providing a biomarker of heart strain, particularly in diagnosing heart failure. Elevated BNP levels suggest that the heart is under pressure, often indicating heart failure, whereas normal or low BNP levels can rule out the condition. The test is especially useful for differentiating between heart failure and other causes of similar symptoms, such as lung disease.
• What factors can affect BNP test results? Factors that can affect BNP test results include age, gender, kidney function, and the presence of comorbidities such as obesity or chronic lung disease. Medications such as beta-blockers, ACE inhibitors, and diuretics may also lower BNP levels, while conditions such as acute myocardial infarction, sepsis, or liver cirrhosis can lead to elevated BNP levels. These factors should be considered when interpreting BNP levels in clinical practice.
• How often should BNP tests be conducted for heart monitoring? The frequency of BNP tests for heart monitoring depends on the patient's condition and treatment response. For stable heart failure patients, BNP may be monitored every three to six months, while those with acute or worsening symptoms may require more frequent testing to assess treatment effectiveness and adjust management. Regular monitoring is essential to guide clinical decisions and evaluate prognosis.
• What does it mean if your BNP levels are outside the normal range? If your BNP levels are above the normal range, it could indicate heart failure or other conditions that cause cardiac strain, such as acute coronary syndrome, severe hypertension, or lung disease. Low BNP levels, while generally normal, could sometimes occur in conditions where the heart is not significantly stressed, or they might suggest other health issues unrelated to heart function.
• Can BNP tests detect conditions other than heart failure? Yes, BNP tests can help detect conditions other than heart failure, as elevated BNP levels can also be seen in conditions such as acute myocardial infarction, pulmonary embolism, chronic kidney disease, and sepsis. However, while BNP is a useful marker for heart failure, its levels can be influenced by various other factors. So, it is important to consider other diagnostic tests and clinical findings when assessing these conditions.
• How is BNP level interpreted in the context of other health tests? BNP levels are best interpreted in conjunction with other diagnostic tests, such as chest X-rays, echocardiograms, and kidney function tests, to form a comprehensive assessment. Elevated BNP levels can indicate heart failure but may also be influenced by lung disease, kidney dysfunction, or other factors, making it important to consider the full clinical context, including patient symptoms and medical history, for an accurate diagnosis.
• What is the significance of high or low BNP levels in diagnosis? High BNP levels are often a key indicator of heart failure, with higher levels correlating to the severity of the condition, but they can also be elevated in other conditions, such as acute coronary syndrome, pulmonary embolism, or kidney disease. Low BNP levels, on the other hand, generally suggest that heart failure is unlikely, but they do not rule out other cardiac or non-cardiac conditions, requiring further clinical evaluation. BNP is a valuable diagnostic tool when interpreted with other clinical findings.
• Are there any preparations required before taking a BNP test? No special preparations are typically required before a BNP test, as it is a simple blood test that can be performed at any time of day. However, it’s important to inform your health care provider about any medications you are taking, as certain drugs, such as diuretics or ACE inhibitors, can affect BNP levels. In some cases, fasting may be requested if additional tests are being conducted at the same time.

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American College of Cardiology: "Pathophysiology and Diagnosis of Constrictive Pericarditis."

Cleveland Clinic: "NT-proB-type Natriuretic Peptide (BNP)."

University of Rochester Medical Center: "BNP (Blood)."

Harvard Men’s Health Watch: "BNP: An important new cardiac test."

American Family Physician: "The Role of BNP Testing in Heart Failure."

Mayo Clinic: "Pulmonary edema."

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