Can you take a pregnancy test a week after sex

Sure if you want.
better after a missed period.

You can take one a week before you have sex... but unless you want to waste your money and time, and want a result that means anything... you have to wait until she's at least two weeks late for her next period.

You can take the test anytime you want. But the accuracy of those tests is less than 50% the first week after a missed period. It increases to over 95% by the end of the second week. So if you want accurate results you wait.

There are some new tests which claim accuracy before you even miss a period. I don't trust them.

Can you take a pregnancy test a week after sex

Not quite yet. If you were ovulating around that time, and did happen to become pregnant, implantation may have just occurred or soon will. This often occurs about 6-12 days after ovulation/conception. The sooner implantation occurs often the better chance for a pregnancy to continue.

Once implantation has occurred, hcg levels will rise substantially. Pregnancy tests manufactured today are often more sensitive than ones produced just 10 years ago. Depending on when you ovulate, when implantation occurs, and the sensitivity of the test used (many these days will pick up just 25 mIU of hcg... a few even less), will determine when you might show a positive result.

Best to wait and see what happens when you would expect your next period. Give it some time if it doesn't show as expected, and then you can try a test... making sure to follow the directions carefully.

Normal to test, when you are late for your next period. Really a waste of money before that. Even then, many will not be correct and show negative, when you are pregnant. So often you will have to wait till you are at least two week late on period to get better testing.

Also always test first thing in the morning with the first urine of day