Before you choose a test you should learn how they work. Home pregnancy tests look in your urine for hCG, human Chorionic Gonadotropin. This is made by the placenta once the fertilized egg (embryo) has implanted into the uterus lining. HCG levels are low at first but rapidly increase, and this hormone causes early pregnancy signs such as food cravings, tiredness, sickness and nausea.
The best time for a pregnancy test is after a missed period as the levels of hCG are high then and easily detectable. On the market are sensitive tests such as Early Response and Clearblue Easy. These can detect lower levels of hCG so can be used earlier, even before a missed period. They can detect levels 20mIU up, so timing is important here. 3 weeks after conception hCG levels could be anywhere between 5 to 50mIU, it varies between women. If your levels are low, the test will give a negative result despite you being pregnant.
The embryo needs anywhere between 6 to 12 days to make that journey to the uterus. During that time there is no hCG and so a negative result would show. A woman should wait at the very least 12 days after conception before testing - and even then it may be too early even for a sensitive test. Note also that if you have taken fertility drugs to conceive a home pregnancy test can give you a false positive result.
The cost of home pregnancy tests ranges from $8 to $20. Some are digital some have lines, but all need to have the directions read carefully. If you are not using a sensitive test wait until after a missed period so that you have enough hCG in your body to be detected. In order to make sure your results are as accurate as can be here are a few tips to follow:
Morning testing is best when the urine has not been diluted. The best urine needs to have been in the bladder for a minimum of 4 hours. Read and follow the instructions precisely. Some will have you put a stick in your urine stream, others might have you urinate in a cup and put the stick in it. Results normally appear after 1 to 3 minutes. After that the test is invalid, so don't recheck after 5 minutes and think your results have changed. If unsure or getting mixed results visit a doctor for a blood test.
All there is to know about an early pregnancy test and pregnancy testing in general. Today's special: when to take a pregnancy test
