Pregnancy tests look for a hormone called human chorionic gonadotropin (HCG) that is only present in a person’s body when they are pregnant. HCG is produced by a pregnant person’s placenta. Pregnancy tests can find this hormone in either your pee or your blood. When the tests find HCG they appear positive for pregnancy. 

At-Home Pregnancy Tests 

At-home pregnancy tests use urine and are 99% accurate when they are used the right way. This is close to the same accuracy as the tests done in your provider’s office. They can be found in most drug stores and are available at a range of prices. At-home pregnancy tests can detect a pregnancy as early as 10 days after conception. However, they may test negative even when you are pregnant if you test too early, as your HCG levels might still be too low for detection.  

To make sure that your pregnancy test results are accurate: 

• Read and follow the instructions for the test carefully. Some tests require you to pee onto a stick, others may have you dip the stick into a cup of your urine, and some may ask you to use a dropper to put your pee in a special container. 

• Make sure that you know what the control line and a positive test result should look like. Tests show positive results in different ways such as a plus sign, two vertical lines, or the word “pregnant”. 

• Take the pregnancy test right after you wake up. This will prevent the HCG levels in your urine from becoming diluted. 

• Wait to take a test until you have missed your period. 

• Make sure that the test is not expired. 

False negatives are common, either from errors taking the test or from taking the test too early. False positives are rare and generally only occur because of a chemical pregnancy, menopause, ectopic pregnancy, or ovarian conditions like cysts. 

Blood Pregnancy Tests 

Blood pregnancy tests are given in your provider’s office. They can be used to find HCG and to determine exact HCG levels. They are generally more complicated and more expensive. Blood pregnancy tests are often only done when needed.