Pregnancy tests can be a source of confusion and anxiety for many people. Depending on the type of test you use, many lines and symbols can appear, often leaving people wondering if the result is accurate or not. One of the most common lines people may see is an evaporation line (also known as an evap line), which appears on certain types of pregnancy tests. This blog post will provide an overview of what an evap line is, why it appears and how to differentiate it from a positive result. It will also provide information on what to do if you think the evap line is a false positive. By understanding what an evap line is and how to recognize it, you can feel more confident and prepared when it comes to interpreting the result of a pregnancy test.
How much HCG does a person need for a positive pregnancy test?
Some prenatal tests claim to find pregnancy five or more days before a period is missed. Although they frequently can, the test’s effectiveness is based on the amount of hCG present in the urine.
The average hCG concentration in urine at 9 days after ovulation, or about 5 days before a missed period, is zero, according to 2014 research. 93 milli-international units per milliliter (mIU/ml).
When hCG levels reach 25 mIU/ml or higher, which occurs after ovulation on or around day 11, most early-result pregnancy tests can be used to confirm pregnancy.
By day 14, hCG levels are typically around 137 mIU/ml. However, for some individuals, they can be as low as 45 mIU/ml.
A pregnancy test’s outcome can be impacted if the day of ovulation is off by 1-2 days because hCG increases so quickly in the early stages of pregnancy.
If a person believes they are on day 11 after ovulation, they can typically anticipate an accurate result; however, if they are actually on day 9 after ovulation, the test might not be able to accurately detect pregnancy.
False negatives are more common than false positives. To give the hCG levels a chance to rise if the test is negative, it may be a good idea to retake it in a few days.
Very few medications, including fertility drugs, may cause false positives. Otherwise, a very early pregnancy loss could be indicated by a positive result followed by a negative result a few days later.
Early in pregnancy, there might not be much hCG in the urine, and the positive line might not be very strong. However, even a weak positive line has color, which sets it apart from an evaporation line, which lacks color. Any coloration in a positive line indicates pregnancy.
An evaporation line may appear as a mark on a pregnancy test if:
The test has failed if the control line on the test does not change color.
A line on a pregnancy test a positive result if:
If someone has not followed the instructions on the test’s packaging, evaporation lines may also appear.
To prevent evaporation lines:
Urine hCG concentrations are often highest when a person wakes up. Taking a test first thing in the morning can increase the chances of an early positive result.
It can be agonizing to wait for a pregnancy test results. The test is probably positive if the result displays a colored line, no matter how faint it may be. A faint, colorless line may be an evaporation line if the results reveal one.
Take two tests and closely adhere to the test instructions as this is a straightforward way to help ensure accuracy.
Those who are uncertain about the results should wait for hCG levels to increase and retest in a few days. This can reduce the risk of false negatives.
By analyzing the blood or urine, a doctor can deliver the most accurate results.
Last medically reviewed on July 11, 2022
What Do Evaporation Lines Look Like?
Evaporation lines are generally more muted than the control line.
Additionally, an evaporation line is typically thinner than a control line. As you can see in the image above, the vertical evaporation line is much thinner and has an uneven thickness while the horizontal line is one thickness.
How long does an evaporation line last?
Evap lines typically don’t appear every time you take a test and typically only appear after the window of time for reading the results.
Reading your results within the time specified in the instructions is one way to reduce the likelihood of the confusion that evap lines can bring about.
Sometimes this is two minutes, sometimes it’s up to 10.
Evap lines do gradually fade and thin with time, but they rarely completely vanish.
It is impossible to restore a pregnancy test to its original color after it has become discolored due to an evaporation line.
How do you tell if it’s an EVAP line or positive?
Do all blue pregnancy tests have evaporation lines?
What does an EVAP line look like on blue dye test?
Do EVAP lines turn dark blue?