No STIs are known to alter the consistency or other appearance of semen. If you do not also have abnormal discharge from the penis or painful urination, I am confident this isn't caused by any STI. However, if you are at risk for STI -- multiple partnerships. partners at high risk themselves, and so on -- it would make sense to have routine testing for common infections, like s urine test for gonorrhea and chlamydia and blood tests for syphilis and HIV. I would expect the results to be negative (and if positive to not necessarily be the cause of the change you have noticed in your semen.)

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD