What Is a BNP Test? Normal, High, and Levels

BNP Blood Test Overview

The NT-proBNP blood test measures brain natriuretic peptide to detect heart failure.
The NT-proBNP blood test measures brain natriuretic peptide to detect heart failure.

If your doctor orders a BNP test, you are probably showing symptoms of heart failure. The test measures a hormone called “brain natriuretic peptide.”

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. That’s why higher levels may be a sign of heart failure.

Emergency departments can get your BNP test results in about 15 minutes.

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.

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. BNP blood tests lead to an accurate diagnosis of heart failure about 90% of the time.

BNP levels can also help your doctor determine your outlook after heart failure. Generally, a higher level means a worse outcome. As levels drop, however, you’ll start to feel better and breathe easier, and your outlook will get better, too.

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

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.

Make sure your doctor knows about all 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.

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 to 400 pg/mL requires a doctor’s evaluation

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

BNP Levels by Ages Chart
ConditionAgesBNP Level (pg/mL)
NormalAnyLess than 300
Possible heart failureUnder age 50More than 450
Possible heart failureBetween ages 50 to 75More than 900
Possible heart failureOver age 75More than 1,800

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. Ask your doctor what your specific results mean for you.

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.

High 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.

If you have high BNP but the doctor rules out heart failure, the levels may point to other conditions such as:

How to Bring BNP Levels Back to Normal

When levels are above the normal range, doctors usually lower them with medication. Your doctor may prescribe ACE inhibitors, beta blockers, or diuretics to help.

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

Conditions that can lower BNP levels include:

Other Tests for Heart Failure

The BNP test is only one way to monitor heart failure. 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.

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.

References
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Medscape: “Brain-Type Natriuretic Peptide (BNP).”

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.”