I just started a new job and I am still enrolled in Medicaid officially. Can I still use Medicaid until my new company sponsored health insurance kicks in?
According to the Medicaid FAQ, it's income that matters, not employment or coverage. So you should be eligible until the job gives you enough income to make you not eligible. This should last at least until your first paycheck. But it may continue after that. If you are $2000 under the income limit and your first paycheck is $1800, it should last until your second paycheck.
Also (from the same FAQ):
Coverage generally stops at the end of the month in which a person no longer meets the requirements for eligibility.
And coverage generally starts for employment-related insurance the first full month after you start. So you should have continuous coverage.
Really though, the people to ask are the Medicaid administrators. Otherwise, you face the possibility that you will use Medicaid as your insurance and have it rejected after approving a medical procedure but before paying for it. Then you could get stuck with Medicaid's portion of the bill as well as your own.
I'm just reading the FAQ, same as you can. I can't guarantee the results. My reading of the FAQ is that you should be covered until the end of the month, and your new coverage should take effect at the beginning of the next month. But you should check with Medicaid on the former and your employer on the latter.