Nitroblue tetrazolium blood test

Toggle: English / Spanish


The nitroblue tetrazolium test checks if certain immune system cells can change a colorless chemical called nitroblue tetrazolium (NBT) into a deep blue color.

Alternative Names

NBT test

How the Test is Performed

A blood sample is needed.

The chemical NBT is added to the white blood cells in the lab. The cells are then examined under a microscope to see if the chemical has made them turn blue.

How to Prepare for the Test

No special preparation is needed.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

This test is done to screen for chronic granulomatous disease. This disorder is passed down in families. In people who have this disease, certain immune cells do not help protect the body from infections.

People who have frequent infections in the bones, skin, joints, lungs, and other parts of the body may have this test done.

Normal Results

Normally, the white blood cells turn blue when NBT is added. This means that the cells should be able to kill bacteria and protect the person from infections.

Normal value ranges may vary slightly from one lab to another. Talk to your doctor about the meaning of your test results.

What Abnormal Results Mean

If the sample does not change color when NBT is added, the white blood cells are missing the substance needed to kill bacteria. This may be due to chronic granulomatous disease.


There is very little risk involved with having blood taken. Veins and arteries vary in size so taking blood may be harder in some people than in others.

Other slight risks from having blood drawn may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)


Glogauer M. Disorders of phagocyte function. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 169.

Riley RS, Mageau R, Ben-Ezra J. Laboratory evaluation of the cellular immune system. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 45.

Version Info

  • Last reviewed on 2/8/2015
  • Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission ( URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2013 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.