What is the injection method and maximum dose for a TB skin test?

• A. Intradermal 0.1 mL
• B. Subcutaneous 0.5 mL
• C. Intramuscular 1 mL
• D. Intradermal 0.5 mL

Answer: (A)

TB skin testing relies on placing a very small amount of purified protein derivative into the dermis so the skin’s immune cells can react locally. The correct approach is to inject intradermally—the tiny amount sits just under the surface of the skin, typically on the inner forearm, and forms a small wheal. The standard dose is 0.1 mL, which provides enough tuberculin to elicit a measurable induration if TB exposure has occurred, without pushing the fluid deeper into subcutaneous tissue or muscle. Using a larger volume or a different route (subcutaneous or intramuscular) can blur the reading and reduce accuracy because those routes don’t provoke the same dermal immune response the test relies on. So, intradermal injection of 0.1 mL is the proper method and dose for a TB skin test.