[AOIIBrandi]

They will hardly ever give a false positive (unless expired, always check the date), but can give a false negative. Listen to PnguinTrax when she says the best and most reliable test is having blood drawn at the Dr.'s office.

Home tests are looking for the presence of a chemical (HCG - I think) that is only present in the body during pregnancy. The problem becomes that some tests look for higher percentages, but don't say it on the box. Most look for around 85% - I believe, where as the Dr.'s test will detect much lower levels. You will not have that high of levels immediately after conception and in some women not till much later, so if you take it the first day you are late it may give you a false negative. You will need to retest in about a week if you still haven't gotten your period. If it gives you a positive you should definitely believe you are pregnant and head straight to the Dr. for confirmation.