How soon after contacting syphilis dies it take to be dected in a bliid test?

Six Weeks: This can vary but it is usually thought to be six weeks. Sometimes in the acute phase the test is so positive that it gives a false negative. So, doctors expert in this will treat an obvious lesion or rash even before the test results are known.

Antibodies tested: The test is for antibodies, which need time to show up post exposure. Fluorescent treponemal antibody absorption (FTA-ABS) test. The FTA-ABS test checks for antibodies to the bacteria that cause syphilis and can be used to detect syphilis the first 3 to 4 weeks after exposure to syphilis bacteria. The test can be done on a sample of blood or spinal fluid.