at least 14 days after sex

But I think its best to wait for a missed period.

i've read alot about hcg levels in the past few days...within one week of pregnancy the hcg levels reach 5 to 50 miu/ml...hcg in a non pregnant woman/man is <10.0 miu/ml...over the counter pregnancy tests can detect the hormone within a week of being pregnant...if it's there you are pregnant, but just because the test comes up negative doesn't mean that you are not pregnant because you may be pregnant but just not producing enough hcg for the test to detect (women produce hcg at varies levels throughout pregnancy, low levels are not necessarily bad)...but i'm not a doctor so only take my info lightly...

I know the waiting is crippling, but it's best to wait until you've missed your period. Otherwise you could end up spending a LOT of time and money weeing on sticks :p (like me!)

The reference range for the hcg hormone is <5, above that would indicate pregnancy, circumstances depending.