A pregnancy test, no matter if it's blood or urine, only becomes positive after implantation when the fetus has attached to the uterine wall and connects with the mother's blood system.
Implantation, when the fertilized egg implants into the endometrium, happens about nine days after ovulation and fertilization (range: six to 12 days). If you are pregnant, then the blood pregnancy test is usually positive within three to four days after implantation or about 10- to 1 days after fertilization and ovulation.
The urine pregnancy test is positive several days after the blood test becomes positive, or around the time you miss your period.
It's best to wait until you are actually late,otherwise you might not have enough pregnancy hormone ( hCG) to register, it'll show negative. Save your money and wait. Be sure to test first thing in the morning.