Had cbc. 34yo male. dad had leukemia. all in range except monocytes % was 3.6l. monocytes # was 0.3 in range. should i worry leukemia or anything else?

No,,: It is common for some individual values to be out of range sometimes. This isn't too low also. What would be worrisome is a consistent pattern of abnormal results. If there were excessive monocytes and blast (immature) cells, for example, that'd be a serious result requiring more tests. This isn't anything like that and there're no other symptoms and signs so it should be fine. Good luck.