Sorry I should have been clearer I guess, I assumed that everyone has 28 day cycles...
NK cells are most active a week prior to your next menstral cycle, so if you do have a regular cycle, work it back about a week, that is the range you are most likely to have your NK cells done. So if you don't O until CD 16-18, I would assume you have a cycle of 30-32, then it will be around CD 25-30. HIH.