A B-type natriuretic peptide (BNP) blood test measures the levels of the BNP hormone in your blood.

BNP and another heart hormone, called atrial natriuretic peptide (ANP), work together to keep your veins and arteries widened, or dilated. This allows your blood to easily pass through and prevents clots from forming. BNP and ANP also help your kidneys more easily remove fluid and salt from your body.

When you have congestive heart failure (CHF), your heart can’t pump blood properly throughout your body because the walls of your heart chambers, known as the ventricles, become tense or too weak. This affects pressure and fluid levels in your heart and throughout your body. When this happens, your heart cells produce extra BNP to help maintain the balance of fluids in your body cells and regulate your blood pressure.

A BNP test detects a rise in BNP, which indicates heart failure. Your doctor may recommend this test if you have symptoms of heart failure, such as shortness of breath. Early diagnosis of heart failure can make sure that you get quick and effective treatment to prevent further complications of CHF.

Your doctor may order a BNP blood test if you have symptoms of heart failure, including:

  • trouble breathing (dyspnea)
  • feeling exhausted or weak for no apparent reason
  • rapid weight gain without a change in diet or activity
  • inability to concentrate or remain alert
  • abnormally high or irregular heart rate
  • coughing a lot, and producing white or pink phlegm
  • nausea or having no appetite

A BNP test can also help rule out heart failure. Other conditions can cause elevated BNP levels, including lung or kidney conditions, or being obese.

No special preparation is needed for a BNP test. You may want to have someone take you home. If you faint at the sight of blood or feel weak from fasting, your doctor may recommend that someone come with you in case you’re not able to drive or get yourself home.

A BNP test is done by drawing blood from a vein in your arm using a hypodermic needle. This process is known as venipuncture.

A machine then measures levels of BNP and another heart hormone, called N-terminal-pro BNP (NT-pro-BNP), in the blood sample.

The results from the test are usually ready in 15 to 20 minutes. Results may take up to a week to be ready if the blood is sent to a separate laboratory facility for analysis.

Your results will indicate if your BNP levels are high enough to suspect a diagnosis of heart failure. If you already have a diagnosis of heart failure, the results can also help your doctor find out if heart failure treatments are helping to treat your condition.

Generally, BNP levels below 100 picograms per milliliter (pg/ml) are considered normal. Levels above 400 pg/ml are considered high. But normal BNP levels may vary depending on your age and sex:

Normal BNP levels by age and sex

less than 45 years old35 pg/ml or below64 pg/ml or below
46–60 years old36–52 pg/ml 46–60 pg/ml
61–82 years old53–91 pg/ml 96–163 pg/ml
83 or older93 pg/ml or below167 pg/ml or below

BNP levels increase naturally as you age. Underlying conditions can raise your levels. BNP tests may be used alongside other diagnostic tests to confirm if you have heart failure or if other conditions are responsible for the increase in your BNP levels.

This test has a 98 percent success rate in diagnosing heart failure as a cause of increased BNP levels.

Exercise can cause BNP levels to rise temporarily. Stress can raise your levels of the hormone cortisol, which can also temporarily increase BNP levels.

To confirm a heart failure diagnosis, your doctor may also recommend the following tests:

Improving your heart health can help reduce the effects of heart failure and other heart conditions. Some healthy steps you can take include:

  • quit smoking
  • drink fewer alcoholic beverages or stop consuming alcohol altogether
  • lose weight
  • relieve stress through yoga or meditation
  • exercise regularly for at least 15 to 30 minutes a day
  • get seven to eight hours of sleep a night

Your doctor may recommend the following depending on the cause of your elevated BNP levels:

If high BNP levels indicate heart failure, your doctor will let you know what steps you need to take to prevent complications of this condition.

See your doctor regularly to monitor your BNP levels. Follow any instructions your doctor gives you to maintain your best heart health.