How many weeks after a missed period should i get a positive pregnancy test ?

Immediately: In the most common setting a urine pregnancy test done on a first morning void would be expected to be positive at the time menses is missed. It can be falsely negative if done early or on a poor specimen, but by a week later should be also. Some normal women occasionally skip a cycle or two when they are not pregnant.

Pregnancy test: Always possible to get pregnant before your missed period. However, most recommendations are that you should wait a week after your last period.