You can get a blood test 7 days after you ovulate, which is usually a week before your period. Blood tests can take longer to process than other methods of pregnancy tests, but a blood test can detect pregnancy earlier and is 99% accurate. You'll get your results back within 1 to 3 days, depending on how busy the lab is. If you don't get them back within 3 days, call your physician.
There are two types of blood tests. One type measures exactly how much hCG is in your blood stream to determine how far along you are in your pregnancy. The other type gives a straight yes or no answer if you're pregnant or not. Both methods take the same amount of time to process.
Even though a blood test can give results sooner than most other methods, there is still a chance of a false reading. Getting the test done too soon can cause a false reading, or the lab can make a mistake. This is rare, however, and blood tests continue to be the most accurate form of pregnancy test.