How soon can a doctor tell if your pregnant?

It is possible for a doctor to detect pregnancy as early as 10 days after conception. At this stage, the levels of the hormone human chorionic gonadotropin (hCG) in the blood can be detected through a blood test. However, most doctors recommend waiting until at least 4-6 weeks after conception before performing a blood or urine test for pregnancy, as the levels of hCG are more reliable at that point.