A pregnancy test attempts to determine whether a woman is pregnant. Markers that indicate pregnancy are found in urine and blood, and pregnancy tests require sampling one of these substances.
Early pregnancy tests can now be taken several days before your period is due – but the earlier you take the test, the less reliable the result. The number of days varies according to the make of pregnancy test. The earliest tests claim to be reliable from up to 5 days before your period is due.
Urine pregnancy tests will only be positive when you have enough HCG in your blood. Most over-the-counter home pregnancy tests will not show that you are pregnant until your expected menstrual cycle is late.
Testing before this will often give an inaccurate result. The HCG level is higher if your urine is more concentrated. A good time to test is when you first get up in the morning.
About video: Find out how pregnancy tests look for the presence of HCG, or human chorionic gonadotropin hormone, with help from a labor and delivery nurse in this free video on pregnancy symptoms.
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