If a woman is pregnant, the amount of hCG in her system should be around 25 mIU at 10 dpo (days past ovulation), 50 mIU at 12 dpo, 100 mIU at around two weeks dpo. Blood tests can determine pregnancy as low as between 5 to 10 mIU/hCG, though with levels of 5 mIU, a conclusive determination cannot be made without risking a "false positive" (as low levels hCG can be present in the body without pregnancy).
Drugstore pregnancy tests generally detect pregnancy at 50 mIU - 100 mIU hCG, though you can find early-detection pregnancy tests on the Internet with sensitivity levels as low as 20 mIU. With all diagnostic products, take care to follow the instructions. Please consult the chart below for a comparison of pregnancy tests:
at 9:28 PM on Jun. 28, 2008