The earliest time to ovulate after HCG is about 24 hours, but this time varies from person to person and is not necessarily the case. In the clinic, HCG can only be used when the follicle has developed to a certain degree, usually when the follicle diameter reaches 18mm after ultrasound monitoring, HCG can be injected intramuscularly under the guidance of the doctor.The follicle will grow rapidly after HCG is injected, and the pressure inside the follicle will increase, and the egg will be discharged, and this time is the fastest for about 24 hours or so. Therefore, intercourse can be arranged about 24 hours after the intramuscular injection of HCG, which can also increase the chance of pregnancy, and in the process, it is also important to maintain a healthy lifestyle in order to prepare for pregnancy. One day after HCG injection, ultrasound examination can be conducted, mainly to observe whether the original dominant follicle has ruptured and discharged eggs to determine the effect of HCG injection. Patients are advised to follow up the treatment as prescribed by the doctor.