1) A dirty cup If you collect your urine in a cup you've used for a test before - if the cup still has traces of old urine, soap or water - the results can be affected.
Use a new cup or buy a pee stick test instead.2) Expired or faulty test Always check the use-by date on a test.
It's most likely to show up when a test is viewed after the recommended reading time has passed, and it can be a different colour to the line that will appear with a positive result.
You should take another test if this happens.3) Prescription medications Some medications contain h CG that can be picked up on a pregnancy test, even when you're not pregnant.
It's best to do a pregnancy test in the morning when your urine is most concentrated.4) Testing late in pregnancy This is very rare, but sometimes if a woman takes a test at the end of her first trimester or later, the test might not detect h CG, as her levels may be higher than the test is designed to pick up.
This is called "the hook effect" and could explain why some women believe they're not pregnant until they give birth, even if they do take a test.
This is called a chemical pregnancy and it's very common.
Follow-up blood tests will be able to tell whether your hormone levels are dropping or rising.2) Evaporation lines Sometimes an 'evaporation line' can appear on a test as urine dries in the test window, and some women may confuse it for a very faint second line.
Implantation usually takes place six days after an egg has been fertilised, but it depends on when conception actually happened, and your cycle length.
For example, if you have a UTI or kidney problems, blood or protein might be in your urine, which can change the test result.
Ovarian cysts, menopause and antibodies can also affect hormone levels.
Blood tests are the best way to measure the exact amount of h CG in the body, but there are also some digital home pregnancy tests that can give you an estimate of how many weeks you are (these will display either 1, 2 or 3 weeks in the window).
Although only a quantitative blood test can confirm a pregnancy completely, using a qualitative urine test at home will probably give you a correct result.