In my childhood i have been vaccinated with hepatitis b vaccine 3 doses, now do i need to do it again? or it has given me a lifetime immunity, as i'm at risk of getting it because i m in hospitals and in touch with patients?

The only way to know if you are still protected would be to check your antibody titer, otherwise you are not at risk of getting it if you are in a hospital and if all protocols are respected strictly.

If you had 3 doses of hepatitis B AND positive hepatitis B antibody test, then you are protected. If not, there is very little downside to having a fourth dose which will give a vigorous response. Thank you for working in the hospital

It would be prudent to get a blood test for antibody to Hep B surface antigen. If your level is less than 10 get a booster and retest, keeping in mind that a small proportion do not make protective level. https://www.cda-adc.ca/jcda/vol-66/issue-10/551.html#:~:text=Levels%20of%20anti%2DHBs%20above,virtually%20complete%20protection%20against%20HBV.&text=Typically%2C%20levels%20in%20the%20100s,10%2