Can you have an STD and it not be detected?

Answer 1

Yes, sometimes even tests can not always detect an STI.

For example: Lesions that are suspected to be Herpes can be swabbed and tested but may not come back as Herpes. Sometimes a blood test can be ordered to find out for sure.

However, with the correct testing for each STI there should be a correct result that is certain. Chlamydia and Gonorrhea should be tested from a swab cultures, viral STI's should be detected by blood.

Answer 2

Most of the time herpes does show up on a test. If it's being tested for, the routine std tests don't always include a test for herpes.

Unless you just contracted it or don't have enough antibodies in your blood to show positive results then it may not show up.