hCG is the abbreviation for "Human Chorionic Gonadotropin," also known as the pregnancy hormone. The pregnancy hormone hCG doubles early on in 1-2 days.
This hormone is produced by the placenta as soon as implantation happens, about one week after fertilization and ovulation. hCG levels in pregnancy continue to rise after implantation until about 10-12 weeks gestation, at which point the hCG level will stabilize or drop.
Pregnancy tests detect the amount of hCG in the blood or urine and a pregnancy test becomes positive when there are sufficient levels of hCG. Blood hCG testing is much more sensitive than urine hCG testing, therefore a blood hCG test can detect pregnancy several days before a urine pregnancy test.
A pregnancy is typically detected by a missed period and implantation bleeding, as well as through typical pregnancy symptoms and early positive pregnancy tests. You can help detect your pregnancy now by doing our online pregnancy test (OPT), and can calculate your hCG with the hCG Calculator.
hCG levels depend on several variable including how many embryoys there are (twins are higher than singletons), when implantation happened (earlier implantation has an earlier rise in hCG, and your body weight BMI (higher BMI have lower hCG levels).
- hCG under 5mIU/ml: Negative, not pregnant.
- hCG between 5-25 mIU/ml: Uncertain; possible pregnancy but not definitive. Repeat test in a couple of days.
- hCG over 25 mIU/ml: You are pregnant!
The presence of a hCG blood level above 25 mIU/ml or a positive urine pregnancy test usually indicate that you are pregnant. However, if you received an hCG injection for fertility then the presence of hCG does not necessarily mean that you are pregnant. In most normal pregnancies with levels below 1,200 mlU/ml, the blood hCG level usually increases by at least 60% every two days though occasionally even a rise below 60% can indicate a normal pregnancy.
What does a single hCG value mean?
A single hCG value above 25 mIU/ml means that you are pregnant. You cannot determine with enough certainty how far along you are or if the pregnancy is viable from a single hCG value. For each day and week of early pregnancies there is a very wide variation of "normal" hCG values which makes it impossible to determine from a signle value what it means exactly except to say that you are pregnant or that you are pregnant within a wide range of weeks and day.
A single hCG level:
- Does no necessarily tell you whether you have twins or a singleton
- Does not tell you if the pregnancy is viable
- Does not tell you exactly how far along you are
There are several possibilities when a Beta hCG level rises slower than expected:
- Sometimes a normal pregnancy can have a slower than expected hCG titer, and the next test will usually show a normal rise. It is quite possible to have a “slow to rise” hCG level and go on to have a normal pregnancy.
- Most commonly, a slower than expected rise indicates a pregnancy that may be failing, such as a miscarriage or a blighted ovum.
- Another possibility is an ectopic pregnancy, which is when the fertilized egg implants itself somewhere other than the uterus, such as the fallopian tube, cervix, or ovary. IVF increases the risk of ectopic pregnancy over natural conception.