Clearblue Easy is an over-the-counter pregnancy test that is sensitive enough to tell a woman that she is pregnant up to four days before her period is expected.
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How it works
The Clearblue Easy test measures the level of a hormone called human chorionic gonadotropin, or hCG, in a woman's urine. The cells that comprise the placenta produce this hormone soon after conception. According to a study published in the Journal of the American Pharmacists Association in 2005 by Laurence Cole and colleagues, Clearblue Easy can detect hCG levels as low as 25 mIU/ml in urine.
If a Clearblue Easy pregnancy test comes back negative, or "not pregnant," this does not necessarily mean a woman is not pregnant. It could be that the levels of the pregnancy hormone hCG have not accumulated enough in the urine. If the test comes back negative, a woman should wait at least three days before taking it again, according to the Clearblue website.
Clearblue Easy is sensitive enough to detect pregnancy up to four days before a woman's expected period. If she does not know when her period should start, she should wait at least 19 days from the time she thinks she may have conceived.
If a woman is taking fertility drugs, the Clearblue Easy test may not be accurate. It may give a "pregnant" result even if the woman is not pregnant.
Clearblue Easy may not provide accurate results in women who have been pregnant for less than two weeks. In clinical tests conducted by Clearblue, the company that manufactures the test, Clearblue Easy correctly diagnoses pregnancy in 82 percent of women who take the test four days before their expected period. This percentage increases to 90 percent for women who take the test two days before their expected period.