Human Chorionic Gonadotropin (hCG)

The hormone produced in pregnancy — what every pregnancy test reads.

hCG is the hormone a developing pregnancy produces almost immediately after implantation — which is why it’s the marker every home pregnancy test is built around. Levels rise quickly in early pregnancy, roughly doubling every two to three days in the first weeks.

What hCG is

Human chorionic gonadotropin is produced by the cells that will become the placenta, starting shortly after a fertilized egg implants. Its job is to signal the corpus luteum to keep producing progesterone, maintaining the uterine lining that supports early pregnancy.

Why levels rise

Once implantation occurs — typically six to twelve days after ovulation — hCG enters the bloodstream and then urine, rising steeply through the first trimester before leveling off. That early, rapid rise is what makes urine testing possible within days of a missed period, and often just before it.

What a result can tell you

A positive result means hCG is present, which almost always means pregnancy. Testing with first morning urine gives the most reliable early reading, since hCG is most concentrated then. A negative result very early on may simply be too soon — retesting after a few days resolves most uncertainty.

What it can’t tell you

A home test can’t tell you how far along a pregnancy is, whether it’s progressing normally, or where it’s located — those answers come from a provider, typically through blood tests and ultrasound. Whatever the result means for you, a healthcare provider is the right next step for confirming and talking through options and care.