Human Chorionic Gonadotropin (HCG) is a hormone that is produced during pregnancy. This hormone is made of cells which form the placenta and are responsible for nourishing the egg when it gets fertilized. The HCG levels can be detected through a blood test conducted about 11 days after conception. Also, a urine test is conducted about 12 to 14 days after conception. Usually, the HCG levels increase two times after every 72 hours. In the first 8 to 11 weeks of pregnancy, the level reaches its peak after which it steadily declines.