Human chorionic gonadotropin (hCG): definition
Human chorionic gonadotropin (hCG) is a hormone made by cells that will become the placenta, starting soon after an embryo implants in the uterus. It keeps the corpus luteum making progesterone in early pregnancy. hCG is what home and blood pregnancy tests detect. In early pregnancy it usually rises quickly, roughly doubling every two to three days.
How it works
- Implantation happens about 6 to 10 days after ovulation.
- Placental cells start releasing hCG into the blood.
- hCG tells the corpus luteum to keep making progesterone, so no period comes.
- Levels peak around 8 to 11 weeks, then fall and level off as the placenta takes over.
| Test | Detects hCG from |
|---|---|
| Blood (beta hCG) | About 5 mIU/ml; often positive 9 to 12 days after ovulation |
| Sensitive urine test | About 10 to 25 mIU/ml; most reliable from the day the period is due |
Check timing with the hCG doubling time calculator and when to take a pregnancy test.
Why it matters
In early pregnancy, doctors may check two blood levels 48 hours apart. A healthy rise is reassuring, while slow rises can point to a chemical pregnancy, miscarriage or ectopic pregnancy. A single number means little on its own, because normal ranges are very wide.
hCG is also used as a "trigger shot" in fertility treatment, which can cause a false positive for up to two weeks. It's the hormone often linked to early pregnancy nausea, and waiting for hCG results can be emotionally intense. Lean on support if you need it.
Get urgent care for heavy bleeding, severe or one-sided pain, shoulder-tip pain or fainting in early pregnancy.
Frequently asked questions
How soon can hCG be detected?
Blood tests can find it about 9 to 12 days after ovulation, sensitive urine tests a little later. Testing on the day your period is due is most reliable.
What does a slow hCG rise mean?
It can mean a pregnancy that isn't progressing or is ectopic, but also sometimes a normal pregnancy. Doctors interpret it with ultrasound.
Sources
This page is for information only and isn鈥檛 medical advice. If something worries you, please talk to a doctor.
Keep reading
hCG doubling time calculator: how fast are my levels rising?hCG doubling time calculator: enter two beta hCG results and the hours between them to see doubling time and 48-hour rise. Your clinic interprets.Pregnancy test: definition and meaningA pregnancy test detects the hormone hCG in urine or blood. How pregnancy tests work, when they're most accurate, and how to read faint lines.
Implantation: definition and meaningImplantation is when a fertilized egg attaches to the lining of the uterus, usually 6 to 10 days after ovulation. What happens, timing and signs.
What is a chemical pregnancy?A chemical pregnancy is a very early loss after implantation, often seen only as a positive test then a period. What it means, signs, and gentle next steps.When should you take a pregnancy test?How soon can you take a pregnancy test? Most work from the first day of a missed period. When early tests work, best time of day, and when to test again.