Does a pregnancy blood test measure weeks since conception?

A pregnancy blood test primarily measures the levels of the hormone human chorionic gonadotropin (hCG) in the bloodstream, which indicates whether a person is pregnant. While it does not directly measure the weeks since conception, healthcare providers can estimate gestational age based on hCG levels and the timing of the last menstrual period. Generally, hCG levels rise in a predictable pattern during early pregnancy, allowing for some estimation of the time since conception. However, it is more commonly used to confirm pregnancy rather than to determine the exact timing.