You will need the name of the employer’s Workers’ Compensation insurance carrier and the employer’s policy number. Either the stage manager or the company manager will have this information. (And hopefully, if your injury requires immediate emergency treatment, someone from the theatre will accompany you to the Emergency Room and handle the insurance questions.) The doctor may try to get your personal insurance information because it will be “easier,” but don’t let them bill your personal insurance. Make sure they use your employer’s insurance.