Evaporation Line On Pregnancy Test

Table of Contents

What is evaporation line?


Evaporation line: what is it?

When you miss your periods, the first thought that pops up in your mind is- am I pregnant? The primary thing women do is to rush to a medical store and ask for a pregnancy test kit to confirm the happy news of their newly found motherliness. The pregnancy test kits come with an instruction leaflet that tries to fill in the user about the test process, but sometimes the test results can be confusing. It can be a nerve-racking experience if you are oblivious to the meaning of lines that appear on the test kit. There is often a faint line where the confirmation line for pregnancy should have appeared on the kit; this adds to the confusion, whether positive or negative. The faint streak that emerges is not an indicator of pregnancy and is called the evaporation line. 

Evaporation lines are a common occurrence that is observed during a home pregnancy test. It is a faint streak that transpires in the result’s window area after the urine sample dries up from the test strip. The urine is likely to leave a faint line after evaporation, called the evaporation line. It happens when the urine is left for more than 10 minutes.  You can misinterpret the line to be a definite line for the test if you are not familiar with the evaporation line’s emergence. It can lead to false-positive results that get turned down after medical examination by doctors. The evaporation line indicates that the test is negative. [1,2,3]

When taking a pregnancy test, you really ought to be certain you follow the directions and do it properly. An evaporation line is one possible way to misread a pregnancy test.

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Evaporation line on pregnancy test


How is that possible? The evaporation line on a pregnancy test appears when the sample urine used for the test evaporates after a certain time. This process is normal and a component of the procedure but leaves behind a colorless but different line. The evaporation line doesn’t appear until after the pregnancy test reading window of time to correctly get your results. So you won’t need to be worried about an evaporation line if you read the pregnancy test within the time specified in the directions that came with your evaluation. For many pregnancy tests, the results will initially appear within five minutes.

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Evaporation lines reasons


Reasons for the development of evaporation lines

Although the home pregnancy test kit is quite handy to use, various reasons can lead to the Evaporation Lines and forge misconception regarding pregnancy status. Some common causes are as follows: 

The test is taken too early: The pregnancy test shows the accurate result if done after a few days of conception. In the initial days, the level of Human Chorionic Gonadotropin hormone is low. As the pregnancy advances, the level of this pregnancy hormone shoots up in the blood and urine, giving a positive pregnancy test. Thus, taking the test too early can give false results.

Faulty Testing: The instructions on the test kit leaflet hold the utmost importance. A careful step-by-step test will yield accurate results, but any standard protocol deviation can lead to false-positive streaks.

Diluted urine sample: The HCG level in the urine is high in the morning owing to its concentrated nature. The intake of fluids throughout the day dilutes the urine, and thus the kit might not be able to detect the HCG levels in the body. 

● The sensitivity of the test: The sensitivity of the test kit differs widely. Test kits with a higher sensitivity level are prone to display accurate results. For instance, a pregnancy test kit with a sensitivity level of 20 MIU will omit chances of erroneous conclusions compared to the kit with 50 MIU sensitivity levels. 

● Chemical Pregnancy: Chemical pregnancy in layman’s terms is an early miscarriage. The test results in a Chemical Pregnancy condition reveals a positive but, but the joy of being a mother is shattered by an early miscarriage that follows. [4]


How does the pregnancy test kit work?


There are two types of test methods to determine the status of pregnancy: 

●       Urine test

●       Blood the

All the pregnancy tests revolve around the principle to detect the presence of Human Chorionic Gonadotropin hormone in the blood and the urine. The Human Chorionic Gonadotropin Hormone is secreted in the female body after the embryo as a result of successful fertilization, gets implanted in the uterus. The implantation occurs after ten days of conception. As pregnancy advances, the HCG level surges in the blood and urine. The urine test kits available in the medical stores detect the HCG and gives a positive line beside the control line to indicate pregnancy. [5]

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Avoiding an evaporation Line


How to avoid the appearance of evaporation lines

The Evaporation line generally appears if the test kit is left with the urine sample for a prolonged period. Some helpful tips can guide you avoid the evaporation lines to pace your way up for an accurate result: 

a.      The test kit’s instructions should be followed remotely close as any form of tangency can lead to a false positive or negative result.

b.     Another common mistake that many women make is checking the results either before time or after the given time frame. If you check the outcome too early, the reaction might not have completed, showing negative results. And if you check after the mentioned time frame, the dried urine sample will likely generate a faint Evaporation Line. 

c.      If the test is taken in the early days of pregnancy, the low levels of HCG can give soft positive lines, and if the urine is diluted, the HCG level drops down, leading to less prominent streak.

Getting an evaporation line to appear on a pregnancy test is essentially a false positive. While true false positives and false negatives are rather rare, the evaporation line is the nearest most women will come to have a mistake on their pregnancy tests. You can completely prevent this mistake by reading the directions and watching your pregnancy test.

The evaporation line is essentially due to studying a pregnancy test after the time limit suggested by the manufacturer has passed. This time limitation is usually clearly stated in the test kit directions. Most pregnancy test kits recommend that you read the results within no more than 10 minutes after the urine test results. The evaporation line is only found on urine pregnancy tests. 

A digital pregnancy test will eliminate misreading a pregnancy test due to how the test results are displayed. You will not have a problem with an evaporation line if you use a digital pregnancy test. This feature is only one of many reasons mothers decide to use a digital pregnancy test. They could avoid the worry about misreading the evaluations negatively or positively.

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Evaporation line vs faint positive


Difference between Evaporation Line vs. Positive Pregnancy Test

There are two lines in the pregnancy test kit called the control line and the result line. If the test is positive, the outcome will be a bold and bright-line similar to the control line within the stipulated time frame. Initially, the line may appear faint, but within minutes it will take the exact width and form of the control line. It is an indication of a positive test line. On the other hand, the evaporation line results from dried urine if the sample is left for too long. It is narrower than the control line and bleak. Another differentiation is that the positive line appears within the reaction time, but the evaporation line does not appear so soon. [6,7]

What Could Cause a Light Line?

A light line may be due to a few things apart from an evaporation line. The light line may be due to a diluted urine sample, meaning the hCG concentration was not high enough to provide a full-blown positive. You might also get a very light line if you take the test too early in the pregnancy, because your hCG levels may not have grown very high yet. It’s important to remember that a positive pregnancy test ought to be considered positive





The evaporation line is a false indicator of pregnancy caused due to faulty testing procedure or late assessment of the result. It can lead to the misconception that a woman is pregnant as a faint line appears. If you confuse with the soft lines on your test kit, seek medical consultation. 

See: Throwing Up Blood While Pregnant


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