Normal blood tests generally do not detect most sexually transmitted infections (STIs) or sexually transmitted diseases (STDs). Some common STIs, such as HIV, syphilis, and hepatitis, require specific blood tests designed to detect the presence of the infection. However, many other STIs, such as gonorrhea, chlamydia, and herpes, require different types of tests, such as urine or swab samples from the affected area, to detect the pathogens. It is important to consult with a healthcare professional or visit a specialized STI clinic for appropriate testing if you suspect you have been exposed to an STI.