Many women save the test once they see a negative result and check it again an hour later. If another line appears hours later, it is an evaporation line and not a pregnancy indicator. While it depends on the type of test you are using, the reaction time is usually 5 minutes for most tests.
Usually the tests recommend waiting about 3 minutes before reading it. If you let the test sit too long the the test may show a false positive result. A false positive is when the tests shows you are pregnant when you actually are not.
This usually ranges between a couple of minutes up until 10 minutes later. If you see a positive result beyond this time frame, you may be left second-guessing the results. However, always remember that a pregnancy test result is only accurate within 10 minutes.
If your pregnancy test results seem to be getting lighter, it could be because you tested after drinking water and your urine was more diluted. Or, the first test result could have been an evaporation line and not a positive result. Test again in the morning for a more accurate result.
How Long It Takes to Appear. If you're checking the result during the window, it's more likely to be a faint positive result. But if you notice the additional line later that day, it's probably an evap line.
A mark on a pregnancy test may be an evaporation line if: More than 10 minutes have passed since taking the test. The mark is faint and colorless, and it resembles a water spot.
A positive result will have a test line that runs from the top of the test window to the bottom with the same thickness and color as the control line. An evaporation line will be a grayish white mark that appears after ten minutes.
Test results should not be read after 5 minutes. Clearblue® Rapid Detection Pregnancy Test: A “Pregnant” result may appear as fast as 1 minute when testing from the day of your missed period. You should wait 3 minutes to confirm a “Not Pregnant” result, or when testing before you have missed your period.
If you had a true evaporation line, future tests will show a negative result. On the other hand, if your test showed a faint line, you should continue to see the line darkening with each day that progresses.
Unfortunately, evaporation lines will not disappear, even when you try to remove them with water. If you are not confident with the pregnancy test result, it's highly recommended that you take another test, taking care to follow the instructions properly, to avoid a false positive pregnancy test result.
It's possible that what you think is a positive test result might actually be a faint evaporation line, or 'evap' line. An evaporation line is a faint line that appears after a pregnancy test with a negative result has dried. Tests that show two line results have what are known as 'indent' lines where the ink pools.
You must wait 3 minutes to confirm a 'Not Pregnant' result, or when testing before your missed period. How long will the result last? The result can be read any time from 3 to 10 minutes. After 10 minutes any change in your result should be disregarded.
It's common to see evaporation lines appear during a pregnancy test, but they don't always. Make sure you check your results within the reaction time if you're using a home pregnancy test. Depending on the brand, this is the window of opportunity to get an accurate result.
Don't Let The Test Sit For Too Long
There is a time limit involved in reading an at-home pregnancy test—if you read the test outside the window of time outlined in the instructions, you could end up with inaccurate results. Most non-digital tests show lines to indicate the presence of hCG in the urine.
Any positive line, no matter how faint, means your result is pregnant. Levels of hCG in your body will increase over the course of your pregnancy. If you test early, your hCG levels may be still be low and you'll see a faint positive line.
During early pregnancy, the amount of HCG in blood and urine rises quickly — doubling every 2 to 3 days. That means if you wait a day or two after your missed period to take the test, and you are pregnant, it's more likely the test will find HCG and show a positive result.
Can a barely visible pregnancy test result be negative? A barely visible pregnancy test result usually can't be negative — because it detected hCG — but it might indicate a false positive or an early pregnancy loss. However, false positive results that are not related to early pregnancy loss are incredibly rare.
Evaporation (Evap) Lines
Evaporation lines are considered false-positive results. Unlike a faint positive result, which will result in a light pink or blue line, an evaporation line does not activate the dye in the pregnancy test, so it may show up as a colorless or translucent line.
Do not read your results until 30 minutes. If the test device is left to develop longer you may receive a false positive result and you will need to repeat the test. This indicates the test is negative. Two lines – even faint lines – indicate the test is positive.
If you saw a faint positive result and retested in a few days with a negative result (or you got your period after testing positive), you may have experienced a chemical pregnancy or early miscarriage. A chemical pregnancy means the egg was fertilized but didn't completely implant.
Can Too Much Pee on a Pregnancy Test Make It Negative? Urinating too much on a urine pregnancy test should not cause a false negative result. But diluted urine, or urine with a higher water content, can impact a pregnancy test by skewing results.
Public Health England reports that RT-PCR assays show a specificity of over 95%, meaning that up to 5% of cases are false positives. The impact of false positive results includes risk of overestimating the COVID-19 incidence, the demand on track and trace, and the extent of asymptomatic infection.