Getting a TB test is straightforward: you can walk into most urgent care clinics, visit your primary care doctor, or contact your local public health department to schedule one. There are two types of TB tests available, and the entire process takes anywhere from one visit to two visits depending on which test you get. Here’s what to expect from start to finish.
Two Types of TB Tests
TB screening uses one of two methods: a skin test or a blood test. Both detect whether your immune system has encountered TB bacteria, but they work differently and each has practical trade-offs.
The skin test (also called the Mantoux test or TST) involves a small injection just under the skin of your forearm. A healthcare worker injects a tiny amount of purified protein from TB bacteria, which creates a small raised bump. You then leave and return 48 to 72 hours later so a trained reader can measure any reaction. If you don’t return within that 72-hour window, the test is invalid and you’ll need to start over with a new one.
The blood test (called an IGRA) requires a single blood draw, similar to any routine lab work. Your blood sample is sent to a laboratory, where technicians measure how your immune cells respond to TB proteins. Results are typically available within 24 hours of lab processing, though it may take several days depending on the clinic and lab. The key advantage: you only need one visit.
Where to Get Tested
Several types of facilities offer TB testing:
- Urgent care clinics are one of the most convenient options. Many chains and standalone urgent care centers offer both skin tests and blood tests without an appointment.
- Your primary care doctor can order either test during a regular visit.
- Local public health departments often run dedicated TB clinics. These tend to accept Medicaid and may offer reduced-cost testing.
- Occupational health clinics specialize in employment-related testing and are a common choice if your employer requires TB screening.
- Independent lab companies sometimes offer walk-in TB blood tests without a doctor’s order.
Before showing up, call ahead. Some facilities only offer one type of test, and not all locations stock the supplies needed for blood tests. If you need results for a specific employer or school, confirm which test format they accept.
What It Costs
Skin tests are generally the cheaper option, often running $20 to $35 out of pocket. Blood tests cost more. As a benchmark, one public health clinic charges $95 for the blood test. Your price will vary by location and whether you have insurance. Many preventive screenings are covered under insurance plans, but some clinics (particularly public health departments) don’t bill insurance directly. They may give you a receipt to submit for reimbursement yourself. If cost is a concern, public health TB clinics are often the most affordable route, especially if you qualify for Medicaid.
Which Test to Choose
For most people, either test works. But the blood test is the better choice in two specific situations.
If you received the BCG vaccine, which is given routinely in many countries outside the United States, the skin test can produce a false positive. The BCG vaccine triggers a skin reaction that looks identical to a true TB infection, and there’s no reliable way to tell the difference. The blood test sidesteps this problem entirely because BCG vaccination does not affect blood test results. If you were born in or spent time in a country where BCG vaccination is standard, ask for the blood test.
The blood test is also preferred if you’re unlikely to return for a second visit. Since the skin test requires you to come back within a strict 48-to-72-hour window, missing that appointment means repeating the entire process. The blood test handles everything in a single visit.
On the other hand, the skin test has been used for decades, is widely available, and costs less. If you weren’t vaccinated with BCG and can easily make two trips, it’s a perfectly reliable option.
Reading Your Results
For the skin test, a healthcare worker measures the firm, raised area (not the redness) at the injection site. The size of that raised area, measured in millimeters, determines whether the result is positive. The threshold varies depending on your risk level. People with weakened immune systems or known TB exposure have a lower threshold, while healthy people with no known risk factors need a larger reaction to count as positive.
Blood test results come back as positive, negative, or indeterminate. An indeterminate result means the test couldn’t produce a clear answer, which can happen if the blood sample wasn’t handled correctly or processed within the required timeframe (8 to 32 hours after collection).
Both tests can produce false negatives if you were exposed to TB within the past eight weeks. It takes two to eight weeks after exposure for your immune system to mount a detectable response. If you’re being tested because of a known exposure, a negative result should be confirmed with a repeat test 8 to 10 weeks after your last contact with the infected person. People with advanced HIV or severe immune suppression can also get false-negative results.
What Happens After a Positive Result
A positive screening test does not mean you have active TB disease. It means TB bacteria have entered your body at some point. The next step is determining whether the infection is latent (inactive, not contagious, no symptoms) or active (the bacteria are multiplying and you may be contagious).
Your healthcare provider will typically order a chest X-ray to look for signs of TB disease in your lungs. They’ll also evaluate your symptoms and medical history. If the X-ray shows anything concerning, or if you have symptoms like a persistent cough, fever, night sweats, or unexplained weight loss, you’ll be asked to provide sputum samples. This means coughing phlegm into a small container, usually three separate samples. The lab examines these under a microscope and runs a culture to check for live TB bacteria. If TB bacteria are found, the lab also tests which medications will be effective against them.
In some cases, your provider may also collect urine or tissue samples to check for TB outside the lungs, though pulmonary TB is the most common form.
Who Needs TB Testing
You probably don’t need a TB test unless something specific prompted you to search for one. The most common reasons include employment requirements (especially in healthcare, education, or corrections), school enrollment, immigration paperwork, or known exposure to someone with active TB.
Healthcare workers should be screened upon hire. The CDC recommends a baseline risk assessment, symptom evaluation, and either a skin test or blood test at that point. Routine annual testing is no longer recommended for healthcare workers unless there’s a known exposure or ongoing transmission at their facility. If a healthcare worker is diagnosed with latent TB and doesn’t receive treatment, annual symptom screening is recommended.
Outside of employment, people at higher risk include those who have lived in or traveled to countries where TB is common, people who have spent time in congregate settings like shelters or correctional facilities, and individuals with weakened immune systems.