yes, it's definatly too early to tell.. if little white hairs start coming out, then your sure it's a female plant.. (unless it's a hermie). and if they frow little "sacs" and no white hairs come out then it's a male plant and you should get it away from the females asap.
give it maybe a week if you are currently in flowering, or if you are still veging, it may take 2 weeks or more