The NHS states that most pregnancy tests can be carried from the first day of a missed period, as this is when they are most reliable. The day of your expected period is when your period is due to begin, the following day is your missed period if you still haven’t started your period by then.
Some tests can be used up to six days before your missed period, or five days before your expected period, due to being much more sensitive. However, if you do the test early, there is the possibility that a negative result may not be completely accurate, as you could still be pregnant due to not yet having enough of the pregnancy hormone, hCG, to receive a positive result.
If you test again on the day of your expected period, the result accuracy rises to over 99%. For those who don’t know when their next period is due, the advice is to do the test at least 21 days after you last had unprotected sex.
