What Does a Positive TB Test Look Like?

m_jpg120056fa (1)Tuberculosis or (TB) as it is often referred to in short is a highly contagious disease caused by TB bacteria present in the air. Although it can affect other parts of the body such as the lymph nodes, it most commonly impacts the lungs. A person can have active Tuberculosis (where the TB symptoms are apparent) or they can have inactive Tuberculosis (where the infection lays dormant in the body and shows no symptoms.)

When Tuberculosis is active it will cause symptoms such as coughing, weakened immune system, malaise, body aches, night sweats, high fever, chills, and sudden weight loss. This disease can also be fatal as it attacks various organs in the body and causes tissue to die.

Worst of all, Tuberculosis is deadly and can prove fatal in it’s active mode!

Getting Tested for Tuberculosis

Mantoux_tuberculin_skin_testOnce you see your family practitioner or go to a clinic to get tested for Tuberculosis a medical professional or a licensed nurse will inject a small dose of antigens (TB proteins also termed as a PPD- Purified Protein Derivatives) into your skin by needle.  The site of injection is always done on the middle of the forearm.

After the Tb proteins are injected the site of the injection will take on the appearance of a small bubble that looks like the picture posted to the left/above.

After this part of the test is complete, you will have to return to where you had the injection performed in 3-days time to get it read to either diagnose you with positive or negative TB..

What Does a Positive Tuberculosis TB Test Look Like?

The erythema does not show a positive PPD test. A negative result will not always look just like the day you received the injection because there may be an induration or another mark still in the spot. Roughly 48 to 72 hours after getting the test, the reaction will be measured in millimeters at the induration. The induration is basically the raised, swollen, hardened area. It is not the redness that is measured, only the swelling. The dimater is measured to see if the person is positive or negative for TB.

As the provider examines your arm, they are able to determine whether or not you have TB or not. They will determine whether or not they need to use a ruler or measuring tape to accurately diagnose you.

In a negative reaction the skin will most likely not be bright red, hard or look affected. It will look similar to the day you received the injection, but there may be a slight redness or indentation.

In a positive reaction the skin will be tough, hard, and take on an inflamed, reddish hue. It will have a large induration. positive Tb test 2

There are 3 main standards of measurement that the Center for Disease Control (CDC) has put into place to gauge whether a person should be diagnosed with a positive Tuberculosis test:

  • 15 MM: If the redness and reaction measure 15 mm or more in anyone with or without underlying health issues they should be diagnosed as TB positive.
  • 10 MM: Children. substance abusers, Immigrants, and those with additional health problems should be diagnosed TB positive if their reaction measures 10 mm.
  • 5 MM: Those who have serious health problems or at are a higher risk for Tuberculosis should and can be diagnosed as positive with a reaction that measures 5 mm.

If you are still wondering “what does a positive TB test look like” please reference the images below:

Negative TB Test


Positive TB Test


What Happens if You Tested Positive for Tuberculosis

If your physician diagnoses you TB positive they will most likely order you to have a chest X-Ray performed. Depending upon how sick you are they may even suggest you be admitted to the hospital to get immediate treatment if you have active TB. If you have dormant TB then your health provider will most likely provide you with antibiotics you can take at home for a duration of time. This preventative measure for those with dormant TB will help aid them to not become active with the disease.

Learn to Recognize the Symptoms of Tuberculosis

Tuberculosis is spread through the air and from person to person. You can only contract the disease from being exposed to someone who has it in its active state. You cannot catch Tuberculosis from someone who has it in its dormant state!

If someone who has the active disease sneezes, coughs, breathes close enough to you and you get in contact with their bodily fluids or airspace- you can catch it.

Tuberculosis can be deadly if not treated with several strong courses of antibiotics. The key to catching it early relies on being aware and educated of the following symptoms associated with TB.

  • Coughing
  • Bloody Phlegm with Cough
  • Chest Pain
  • Night Sweats
  • Shaking Chills
  • High Fever of 101 degrees fahrenheit or more
  • Malaise
  • Weight Loss
  • Fatigue
  • Loss of Appetite

In order to protect yourself from the likes of this heinous disease or if you are suffering from relative TB symptoms, you should immediately seek medical attention and opt for what is known as a TB test (Mantoux tuberculin Test.)

Note: The symptoms of TB (Tuberculosis) are often commonly related to other types of sicknesses, diseases, and health problems. Just because you have these symptoms it does not necessarily mean you have TB, however it is in your best interest that you get tested so that your doctor can rule out TB and help you to also diagnose any other problem that may be causing the symptoms.


  1. Hey i’ve got another problem i got the TB test 2 days ago and i don’t know if i can get it checked with the 3 days becayse the clinic is closed tomorrow. Can i go get it checked even though its more than 3 days after also if i do have to redo everything can i get them side by side because i have a deadline to hand the reports in is there a restriction on it?

    • You will have to just go back to the clinic as soon as possible. They presumably knew that they would be closed, so they must not have thought that it would be a problem. In the meanwhile, try not to scratch it. You may also want to call the clinic and see if it would be alright for you to come in today instead. The bump will often develop within the first two days, so it may be late enough for them to check the results already.

  2. got a TB test on Tuesday I’ve scratched it on diffferent occasions when i took baths and soap has maybe gotten into it. im hoping to get it checked on tomorrow but it kinda swole up and elevated. i have taken a TB test befor and it was negative but i dont know what this one will say because of the scratching.

    • It seemed like you commented twice on this one. I have to answer and approve each comment individually, so it may take me a little while to answer all of them. If you do not see a response right away, do not worry because you will. Read through my last response and let me know if you have any other questions. Thanks for commenting!


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