I was always led to believe about 2 weeks - definitely with blood tests. I used to do a lot of preg tests when I was in pathology, and blood test is good after about 10 days, as thats how long it takes for detectable hcg to appear in the blood. Pee test it may take a little longer, as your kidneys can filter out some of the beta-hcg, so really low levels may not show straight away. If ever in doubt, go to the docs and get a blood test - always more reliable.