Hi, blood cells during urination is called haematuria. Causes of haematuria includes
kidney problems, urinary tract infections, kidney or bladder stones, viral infections,kidney infections, kidney injury, cancers, some medications and physical injury to urethra.
If bleeding is at starting of urination may indicates urethral injury. If bleeding at the end or continous indicates bleeding site may be at bladder and above. Consult general physician and urologist for furthur evaluation and treatment.