The Clearblue Digital Ovulation Test detects the rise of the ovulation hormone LH (luteinizing hormone) 24 to 36 hours prior to ovulation and identifies the 2 best days to conceive in a given cycle. It's more accurate than calendar and temperature methods and gives you clear results on a digital display. This test accurately tracks your personal levels of 2 key fertility hormones and identifies additional high fertility days, giving you more opportunities to get pregnant. Clear results are provided, with a unique 'smiley face' appearing on your fertile days. The test can be adjusted every time you use it according to your unique hormone profile. The Clearblue Digital Ovulation Test is over 99% accurate in detecting the LH surge in urine and uses established technology for reliable results. It's simple to use and provides clear digital results for greater accuracy in your hands.