If the basal body temperature has been high for 13 days and pregnancy has not been detected, it may be due to improper testing, incomplete atrophy of the corpus luteum, and self-factors. 1. Improper testing: If you are using early pregnancy test paper to test, improper testing, such as: drinking too much water before the test, not following the instructions to operate correctly, etc., may lead to false-negative test results. 2. Luteal atrophy: the basal body temperature is high for 13 days, and pregnancy is not detected, which is an abnormal phenomenon and may be caused by luteal atrophy, which is often accompanied by symptoms such as delayed menstrual cycle and prolonged menstrual period. 3. Self-factors: some women, before measuring the body temperature, if there is a big change in room temperature, have sex, emotional irritability and other factors, may also have an impact on the body temperature, resulting in an increase in body temperature. Appear basal body temperature continues to be high for 13 days, has not been measured the phenomenon of pregnancy, it is recommended to consult a doctor in a timely manner, combined with the woman’s own condition after the doctor’s visit to make a comprehensive judgment, targeted treatment.