When is the earliest to take a hpt? can i take one before i'm suppose to miss my period?

You may: Hpt can turn positive just before a missed period, but a negative result at that time will not rule out pregnancy. You should wait 4-5 after a missed period to do the test. Use first morning urine and follow the instructions carefully. A blood test does turn positive sooner.

4 weeks after LMP: Take home pregnancy test as directed/instructed. Should wait until 4 weeks after last menstrual period. In other words, take test after you've missed your period, not before.