Can A Pregnancy Test Give A False Negative?
Most of the time, getting a negative result on a pregnancy test means that you are probably not pregnant. But there are a few situations in which a pregnant woman could, theoretically, get what's called a "false negative" on a pregnancy test.
Testing Too Early
Pregnancy tests will always be more accurate if you wait until your period is late before testing. Even a test marketed as giving an early answer can give you a false negative if you test before your menstrual period is due. For example, say that you tend to have a typical, 28-day menstrual cycle. You're more likely to get an accurate reading from a pregnancy test if you wait until you haven't had a period for at least 29 days. To be extra safe, you might even consider waiting (if you can stand it!) until day 36, since menstrual cycles in adult women can be anywhere from 21 to 35 days long. (Menstrual cycles in young teens can even be as long as 45 days.)
Not Conducting the Test Properly
If you make a mistake while using the test, such as not using enough urine on the test stick or not waiting long enough to see a result, you may get an incorrect result. But usually, if the control line shows up, your test result should be accurate.
Testing Late In the Day
In early pregnancy, it is possible that drinking a lot of water during the day and testing in the afternoon or evening could affect the accuracy of the test. When urine is diluted, it's harder for an at-home pregnancy test to determine whether hCG is present. That's why most pregnancy test manufacturers recommend testing first thing in the morning. But this should be a factor only in the first few days after your missed menstrual period; after that, usually, even a test later in the day should give a positive result.
Negative Test After Positive Test
If you get a negative pregnancy test after having previously had a positive pregnancy test, you may be having a miscarriage—especially if you are also having abdominal cramping and vaginal bleeding and if you notice the loss of any pregnancy symptoms (such as fatigue, nausea, and sore breasts). But there is a slim chance that one of the issues in the bullets above might be affecting the accuracy of your second pregnancy test if you are still in very early pregnancy. When in doubt, call your doctor's office for advice.