How many days at least after exposure to syphilis can have the exact result?

Six weeks: The standard syphilis blood tests become positive as early as 2-3 weeks after infection, but it can take up to 6 weeks. If your last possible exposure was 6 weeks or more earlier, a negative test is conclusive. Absence of symptoms also is a good sign you weren't infected. Syphilis usually causes an obvious sore (chancre) at the exposed site.