How can I have an STD if my STD test results are negative?

No single test screens for all sexually transmitted diseases (STDs). Some require a vaginal exam and others require blood or urine tests. And just because you have a negative test doesn't mean you don't have the disease. Gonorrhea, for example, may travel far up into your reproductive tract, so your doctor is unable to obtain a culture. Or your body may not have developed enough antibodies to a virus like human immunodeficiency virus (HIV) to turn up in a blood test. Still, it's important to ask your healthcare provider to regularly test you for STDs if you're sexually active in a nonmonogamous relationship (or have the slightest concern about your partner's fidelity).