Tuberculin Skin Test – Indications, Procedures, Results

Last updated: February 8, 2026 Medically reviewed by: RxHarun Orthopedic Specialist Doctor Reading time: 4 min read

PPD skin test

Purified protein derivative standard; TB skin test; Tuberculin skin test; Mantoux test

The PPD skin test is a method used to diagnose silent (latent) tuberculosis (TB) infection. PPD stands for purified protein derivative.

How the Test is Performed

You will need 2 visits to your doctor’s office for this test.

At the first visit, the health care provider will clean an area of your skin, usually the inside of your forearm. You will get a small shot (injection) that contains PPD. The needle is gently placed under the top layer of skin, causing a bump (welt) to form. This bump usually goes away in a few hours as the material is absorbed.

After 48 to 72 hours, you must return to your provider’s office. Your provider will check the area to see if you have had a strong reaction to the test.

How to Prepare for the Test

There is no special preparation for this test.

Tell your provider if you have ever had a positive PPD skin test. If so, you should not have a repeat PPD test, except under unusual circumstances.

Tell your provider if you have a medical condition or if you take certain medicines, such as steroids, which can affect your immune system. These situations may lead to inaccurate test results.

Tell your provider if you have received the BCG vaccine and if so, when you received it. (This vaccine is only given outside of the United States).

How the Test will Feel

You will feel a brief sting as the needle is inserted just below the skin surface.

Why the Test is Performed

This test is done to find out if you have ever come in contact with the bacteria that causes TB.

TB is an easily spread (contagious) disease. It most often affects the lungs. The bacteria can remain inactive (dormant) in the lungs for many years. This situation is called latent TB.

Most people in the United States who are infected with the bacteria do not have signs or symptoms of active TB.

You are most likely to need this test if you:

May have been around someone with TB
Work in health care
Have a weakened immune system, due to certain medicines or disease (such as cancer or HIV and AIDS)

Normal Results

A negative reaction usually means you have never been infected with the bacteria that cause TB.

With a negative reaction, the skin where you received the PPD test is not swollen, or the swelling is very small. This measurement is different for children, people with HIV, and other high-risk groups.

The PPD skin test is not a perfect screening test. A few people infected with the bacteria that cause TB may not have a reaction. Also, diseases or medicines that weaken the immune system may cause a false-negative result.

What Abnormal Results Mean

An abnormal (positive) result means you have been infected with the bacteria that cause TB. You may need treatment to lower the risk of the disease coming back (reactivation of the disease). A positive skin test does not mean that a person has active TB. More tests must be done to check whether there is active disease.

A small reaction (5 mm of firm swelling at the site) is considered to be positive in people:

Who have HIV
Who have received an organ transplant
Who have a suppressed immune system or are taking steroid therapy (about 15 mg of prednisone per day for 1 month)
Who have been in close contact with a person who has active TB
Who have changes on a chest x-ray that look like past TB

Larger reactions (larger than or equal to 10 mm) are considered positive in:

People with a known negative test in the past 2 years
People with diabetes, kidney failure, or other conditions that increase their chance of getting active TB
Health care workers
Injection drug users
Immigrants who have moved from a country with a high TB rate in the past 5 years
Children under age 4
Infants, children, or adolescents who are exposed to high-risk adults
Students and employees of certain group living settings, such as prisons, nursing homes, and homeless shelters

In people with no known risks of TB, 15 mm or more of firm swelling at the site indicates a positive reaction.

People who were born outside the United States who have had a vaccine called BCG may have a false-positive test result.

Risks

There is a very small risk of severe redness and swelling of the arm in people who have had a previous positive PPD test and who have the test again. This reaction can also occur in a few people who have not been tested before.

Frequently Asked Questions

Is this article a replacement for a doctor?

No. It is educational content only. Patients should consult a qualified clinician for diagnosis and treatment.

When should I seek urgent care?

Seek urgent care for severe symptoms, rapidly worsening condition, breathing difficulty, severe pain, neurological changes, or any emergency warning sign.

References

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Written by Dr. Harun Ar Rashid, MD - Arthritis, Bones, Joints Pain, Trauma, and Internal Medicine Specialist

Dr. Md. Harun Ar Rashid, MPH, MD, PhD, is a highly respected medical specialist celebrated for his exceptional clinical expertise and unwavering commitment to patient care. With advanced qualifications including MPH, MD, and PhD, he integrates cutting-edge research with a compassionate approach to medicine, ensuring that every patient receives personalized and effective treatment. His extensive training and hands-on experience enable him to diagnose complex conditions accurately and develop innovative treatment strategies tailored to individual needs. In addition to his clinical practice, Dr. Harun Ar Rashid is dedicated to medical education and research, writing and inventory creative thinking, innovative idea, critical care managementing make in his community to outreach, often participating in initiatives that promote health awareness and advance medical knowledge. His career is a testament to the high standards represented by his credentials, and he continues to contribute significantly to his field, driving improvements in both patient outcomes and healthcare practices. Born and educated in Bangladesh, Dr. Rashid earned his BPT from the University of Dhaka before pursuing postgraduate training internationally. He completed his MD in Internal Medicine at King’s College London, where he developed a special interest in inflammatory arthritis and metabolic bone disease. He then undertook a PhD in Orthopedic Science at the University of Oxford, conducting pioneering research on cytokine signaling pathways in rheumatoid arthritis. Following his doctoral studies, Dr. Rashid returned to clinical work with a fellowship in interventional pain management at the Rx University School of Medicine, refining his skills in image-guided joint injections and minimally invasive pain-relief techniques.