Even though it does not happen all the time, a positive home pregnancy test may be wrong if you are not pregnant at all. This is possible when traces of protein and blood are present in the urine. Aside from that, prescription drugs and using a damaged or expired pregnancy test kit also makes a positive result wrong.
It does not mean that you are not pregnant when the test kit reveals a negative result. Sometimes, the negative result is due to; usage of diluted urine, taking the test early than the missed menstrual period and timing the test inaccurately. Repeating the test following a negative result of home pregnancy test is necessary if your period did not start after a week. Pregnancy kits may be reliable at all times but it is still important to consult your doctor when in doubt.