How to tell if you have an STD by Business Insider Plenty of illnesses announce their arrival with annoying or even alarming symptoms. But sexually transmitted diseases (better known as STDs) often don't. "In general, we say that most STDs are mostly asymptomatic," Dr. Charlotte Gaydos, a professor in the division of infectious diseases Johns Hopkins University School of Medicine, told INSIDER. That means you might have an STD for a long time — potentially spreading it to sexual partners and leaving yourself at risk for health complications — but have no idea you're infected. This lack of symptoms is particularly prominent for certain STDs. For example, most people with chlamydia have no symptoms, according to the Centers for Disease Control and Prevention (CDC). This is especially true for women: Up to 80% of women with the infection don't have them, Gaydos said. About half of women also don't show gonorrhea symptoms, Gaydos added (but men us...