It would depend upon the reason for the blood work-up.
If you went in because of an issue you are having and they did blood work in an effort to find causation, then yes, I would think you would have (should have) heard something by now. If it was just a routine annual physical and they drew blood for routine workups, then no... in that case, you will likely only get a card in the mail if the results are normal, and possibly a phone call if something is "off". I would expect a phone call for certain if something was dramatically out of whack, though.
But, if you went in b/c you are concerned about some symptom you are experiencing and they were running tests to figure out what is going on, I would call them tomorrow and find out what the results were.
Offices get swamped, and sometimes blood work results can get filed away without the phone call being made or whatever. Mistakes happen.
So I would follow up myself, with a phone call tomorrow.