1 month old baby wbc is 11.5 what can be the cause and the doctor can't give her anything because she is to small she said should i be worried?

Not necessarily: 11, 500 WBC count by itself is well within the normal range for a newborn & first year. But by itself, one test value provides only a partial picture of any situation. It needs to be put into the context of symptoms, reason for the test, past values and the breakdown of the various types of wbc's. If all the wbc's are neutrophils or lymphocytes, it would be worrisome for different reasons.