I was wondering if you could better explain to me in detail how blood tests detect hcg in more detail than google could.

Dr Google: Not sure what you got from google but HCG is a hormone that is produced by an implanted embryo after conception. Labs can measure it in the blood and it is excreted in the urine (urine pregnancy test.) It doubles about daily in your blood up to approximately the first trimester and tends to level out and drop a bit during the rest of pregnancy. There are some cancers that can also produce it.