I don't think simply getting a card will void your license, however it could definitely be grounds for termination in whatever facility you work at. If you're conerened about it, 8 would contact someone at your place of employment of the state license board
I must disagree with CannaBear. If your a nurse, doctor, politician, or in ANY profession or job, your having a MMJ will not, BY ITSELF, influence your job or be grounds for termination. No one other then HelloMD knows that you a MMJ recommendation and unless you decide to tell your employer that you have one, they will not find out.
However, if you USE cannabis and your job does random drug urine testing and you test positive, your job and license could be in jeopardy.
You can voluntarily register with the State of California to obtain a State ID card if you want. This is not mandatory to purchase cannabis and is in a "secure" database according to the State. Your employer is not entitled to see this database.
Perry Solomon, MD