Home pregnancy tests can find the presence of a pregnancy hormone (called human chorionic gonadotropin, or hCG) in a sample of urine. If you are pregnant, most tests show a color change or a symbol shows in the indicator area of the test strip or on the part of the test device.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
Taking the test very early in your pregnancy. HCG may not be found. In this case, the test kit may show that you are not pregnant when you really are pregnant. This is called a false-negative result. If you have drunk a lot of fluid, your urine may be diluted and this may also cause a false-negative result.
Certain things may cause the test results to show that you are pregnant when you are not pregnant. This is called a false-positive result. False-positive results may be caused by reading the test at the wrong time, letting the test equipment get warm, having protein or blood in the urine, or having hCG hormone in the urine from some other cause.