Age 15. ejaculated blood mixed with sperm. went to urinate after, and there was no blood in my urine. no pain either. what might this be?

The medical term for blood in semen is hematospermia. In most cases it isn't serious. It can be spontaneous, i.e. no obvious cause. It also can result from trauma to the perineum (the space between testicles and anus), e.g. from rough-road cycling, horseback riding, etc. If it continues, see a doctor, preferably a urologist. Good luck.

Are you21 or asking for someone 15?.Blood in ejaculate usually comes from inflammatory conditions of the prostate or seminal vesicles. The person needs to be seen and examined by a Urologist for proper management.