how long after you've had sex can you take a pregnacy test if you think your pregnant?
Usually on the first missed day of your period.The urine test and the blood test in a doctor's office can detect approximately 7-10 days after conception. The home pregnancy tests usually detect about 14 days after conception (around time of period). So you'd have to know when you ovulated and when you copulated, then calculate it all.
About Home Pregnancy tests: The pregnancy hormone, HCG (Human Chorionic Gonadotrophin), is produced when a woman becomes pregnant. Pregnancy tests detect the presence of this hormone in a woman's urine or blood. If a test result is negative, HCG has not been detected and a woman is probably not pregnant. It is advised, however, to re-take the test after one week to ensure that a woman's menstruation cycle has not been miscalculated.
If the test shows a negative result, wait another few days or a week and try again if you still haven't gotten your period. (If you ovulated later in your cycle than you thought, you may have taken the test too early to get a positive result.) For best results, try taking the test first thing in the morning, when your urine is most concentrated.
Whatever you do, don't assume that one negative result means you're not pregnant. If you don't get your period as expected, remember that you might still be pregnant (it's no time to go off on a drinking binge or do other things that are unsafe in pregnancy). If you still haven't gotten your period or a positive result in another week or so, make an appointment with your practitioner so you can try to find out why.
Many instructions will say that you can start as early as the first missed day of your period. However some women are different, so you can try taking the test at least 5 days after to give your hormones some time to react.