You should take a pregnancy test starting from the first day of your missed period for the most reliable result. Some pregnancy tests are sensitive enough to detect pregnancy hormone (hCG) a few days before your missed period, as early as 6 days before, but testing too early increases the chance of a false negative result because hCG levels may not be high enough yet. For the best accuracy, it is recommended to wait about a week after your missed period to take the test. If your menstrual cycle is irregular and you don't know when your period is due, take the test at least 21 days after unprotected sex or if you're concerned your birth control may have failed. Taking the test with your first morning urine or holding urine for several hours before testing can also increase accuracy since hCG concentration is higher. In summary:

• Best time: First day of a missed period.
• More accurate: One week after missed period.
• Early tests: Some detect pregnancy up to 6 days before missed period.
• If irregular cycle: Test 21 days after unprotected sex.

If you test early and get a negative result but still suspect pregnancy, test again a few days later or after your period is due.