Yes, it is possible to have an STD and show no symptoms. This is why it is important to get tested if you think you have had a sexual partner that could have an STD and to get regularly checked for STDs. You may not know your partner is infected unless he or she tells you. Some STDs don't show any symptoms, so your partner may not even know if he or she is infected. If you or your partner has had unprotected sex, you may have an STD and not know it. The only way to know for sure is to be tested. STD testing is a good idea for ANYONE who is sexually active.