# BBT is lower before ovulation > During the follicular phase of the menstrual cycle, BBT keeps in the lower range, generally between 97.0 and 98.08F, until approximately 1 day before ovulation, when BBT reaches its lowest point (nadir, or dip).[[(Su et al., 2017)#^4t3se]] > Preovulatory = around 36.4 (97.5) or higher[[Fertility Awareness Mastery Charting Workbook Lisa Hendrickson-Jack#^9w1yp]]