The hCG blood test is used to confirm pregnancy and estimate how far along you may be. This test measures levels of the hormone hCG (human chorionic gonadotropin), which is produced only during pregnancy.
Tracking hCG levels can help doctors monitor early pregnancy development and detect possible complications. Because hCG rises in a predictable pattern during the first weeks, it is often used as a guide to estimate gestational age.
Use our hCG calculator below to check your result and see how many weeks pregnant you might be:
What is hCG?
Beta-hCG, or simply hCG, stands for human chorionic gonadotropin. This hormone is normally produced during pregnancy and is linked to many common pregnancy symptoms. It is most often measured with a blood test to confirm if pregnancy has occurred.
An hCG blood test may be ordered as either quantitative or qualitative. A quantitative result provides the exact level of hCG in the blood, while a qualitative result simply indicates whether hCG is present or not.
Learn more about the hCG hormone and how to interpret results.
How does hCG predict gestational age?
After fertilization, hCG production begins and rises quickly in the first trimester. Levels usually peak around the 12th week of pregnancy and then gradually decrease until delivery.
Because hCG follows a predictable pattern, measuring hCG levels can help estimate gestational age.
hCG levels chart by week
Doctors often compare your result to standard ranges of hCG levels by week, as shown in the chart below:
Why isn't hCG detectable in the first weeks of pregnancy?
hCG is only produced after the embryo implants in the uterus, which usually happens between the second and third week of pregnancy. Before implantation, hCG levels remain extremely low.
Because of this, very early blood tests may not detect hCG, and urine pregnancy tests are even less sensitive at this stage. That’s why testing too soon after conception can give a negative result, even if you are pregnant.
How to interpret hCG results
The hCG calculator uses your result to estimate gestational age by comparing it to the standard ranges in the chart above.
Sometimes a single value may match more than one possible week of pregnancy. In these cases, it’s important to also consider the date of your last menstrual period for a more accurate estimate.
For example:
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An hCG level of 3,800 mIU/ml may fall into the 5–6 week range
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The same value could also overlap with the 25–40 week range
In this case, a pregnancy that is further along would almost always be closer to the later range.