A pregnancy test is used when a woman is testing to see if she is pregnant and can be taken about 14 days after intercourse. When a woman is pregnant, the human chorionic gonadotropin (HGG) hormone gradually increases in the body after the fertilized egg settles in the lining of the uterus. At about 14 days after sexual intercourse, the level of human chorionic gonadotropin in the urine is enough to be detected by a pregnancy test, so you can use a pregnancy test to detect pregnancy at this time. It is generally recommended that the first urine of the morning be used for the test, as this is the time when the urine is concentrated and the concentration of human chorionic gonadotropin in the urine is relatively high. Women can read the results within five minutes after taking a pregnancy test, and if there are two red bars, it indicates pregnancy. However, it is important to note that pregnancy tests are only valid for five to ten minutes, and if two bars appear on a pregnancy test after two to three hours, it is a false positive and inaccurate. In addition, when using a pregnancy test, you must pay attention to its shelf life and whether it has been opened, if it is opened for a long time or after the shelf life, it may affect the accuracy of the pregnancy test.