Psa prostatic specific antigen of my father is 1.87 ng/ml is that normal?

Normally 0 to 4: Minor variability among laboratory reference range, but normally between 0-4 is considered normal. But, for some one who had a total prostatectomy (removal of prostate for cancer etc..), any level above 0 is considered abnormal. So, usually 1.8 is normal, but the rate of change is also of some importance. Follow up with doc regularly. Good luck.