HCG doubling in three days is usually normal. HCG does not double at all times, normally, HCG should double every other day when it is 2000 U/L, and doubling once in three days is also normal. When the value is between 2000-6000U/L, it doubles once every three or four days, but doubling once a week is also abnormal. While observing the doubling of HCG, an ultrasound can be performed at the gynecology department of the hospital to check the development of the gestational sac and to rule out ectopic pregnancy. If the HCG value and progesterone value are low through blood test, it is easy to cause miscarriage. It is recommended to take progesterone reasonably under the guidance of doctor, and it is also recommended to supplement vitamin E reasonably, which can prevent miscarriage.