Evaporation Line on Pregnancy Test: Causes & How to Avoid It

Evaporation Line on Pregnancy Test – What Exactly Is It?

Medically Reviewed By
Dr. Sabiha Anjum (Gynecologist/Obstetrician)
View more Gynecologist/Obstetrician Our Panel of Experts

Every time women buy a pregnancy test kit, it is assumed that they already know how to use it well. The instructions present on the kit do their best to cover all possible scenarios and instructions on the best way to use it. But sometimes, there can be certain results that may not exactly reveal whether you are pregnant or not. They can even be interpreted to mean one thing when it is actually the other.

How Does a Home Pregnancy Test Work?

All pregnancy kits work on the same principle, no matter which brand or company has manufactured them. They all consist of a stick, which needs to be peed on and given some time for it to display the result. What the sticks do is check the presence of a hormone called hCG. Termed as human chorionic gonadotropin hormone, this is a primary sign for a woman to be pregnant and is present in good quantities, especially in the first urine of the morning.

What Is an Evaporation Line on the Test?

Every kit has a specified amount of time within which it displays the result. This time is usually somewhere around 5 minutes. If the stick is left around longer than that, what happens is that a faint line appears on the area where the result is displayed. This line is termed as an evaporation line in a pregnancy test. Women wondering how common are evaporation lines present on the stick should know that there have been various cases mentioning them. Any deviation from the specific instructions mentioned on the pregnancy kit can result in their appearance in the display area.

How to Identify the Evaporation Lines on a Pregnancy Test

The test result lines and the evaporation lines are rather distinctive. In the process of figuring out what colour is the evaporation lines on pregnancy tests, one major thing to remember is that they can be distinguished to be separate from the norm.

These lines are usually colourless but, at times, could have a very faint colour to them. They are not as bold and vivid as the display result lines. These evaporation lines do not appear on every single pregnancy test for every woman. At times, the chemical composition of your urine could cause an evaporation line to appear as well.

If the results of the pregnancy stick are checked well within the stipulated time mentioned in the instructions, the chances of spotting an evaporation line are negligible.

Causes of Evap Lines

The evaporation lines are known to occur mostly when the pregnancy test stick is left by itself longer than the time mentioned in the kit instructions. In such a case, the urine on the stick starts evaporating and may cause a second line to appear, which is termed as the evaporation line. At times, a pregnancy stick with a different sensitivity level than usual ones could also result in the formation of a faint coloured line.

How to Avoid Getting Evaporation Lines on Pregnancy Test

The instructions mentioned in a pregnancy kit are absolutely instrumental in achieving a conclusive and strong result that signifies the presence or absence of your pregnancy.

Since the pregnancy sticks function on the presence of the human chorionic gonadotropin hormone in the urine, it is necessary to ensure that your urine contains the highest proportion of it, if you were to be pregnant. This can be achieved by using the first urine of the day for the pregnancy test since it has a better chance of containing large proportions of the hormone.

Checking the pregnancy stick at the right time is necessary as well. Checking too soon will, unfortunately, yield nothing. Checking too late could cause the urine on the pregnancy stick to dry out, and result in the formation of an evaporation line. This could lead you to believe that you are pregnant when, in fact, you are not.

How to Avoid Getting Evaporation Lines on Pregnancy Test

Any diluted urine or using a brand of pregnancy kit that is not well known could cause the stick to display a faint line on it, which may or may not be an evaporation line. Therefore, it is necessary to use the right kit and the right time of urination.

How Is Evaporation Line Different From a Positive Pregnancy Test?

  • An evaporation line is displayed only after the stick has been out for more than the stipulated time. The line that appears on it as thin and colourless, and cannot be spotted easily.
  • A positive pregnancy test, however, is revealed with a strong and bold line and is quite thick. It can be easily seen and stands out by itself.

Difference Between Faint Positive Pregnancy Test and Evap Line

  • A faint positive pregnancy test reveals itself to be displayed on the pregnancy stick in the form of an absolutely thick line which is exactly of the same width as the control line. As for an evaporation line, since that occurs due to the urine drying out, it is comparatively thinner than the control line on the kit, as well as isn’t as vivid as the other.
  • The reaction time is an important key in distinguishing this aspect. If you are pregnant, then the pregnancy line on the kit will be displayed within the reaction time mentioned on the pregnancy kit. The evaporation line does not appear so soon and requires the urine to dry out to be displayed. Therefore, if the evaporation line is seen, that means you have let the pregnancy stick be by itself for longer than needed.
  • When a pregnancy test line is displayed, it has the exact same colour as that of the control line of the kit. Certain kits might have a different colour but they are usually vivid and easily discernible. An evaporation line cannot be spotted as easily as that. They are usually colourless and even if there is any colour, it is primarily greyish or off-white, which is also rather dull and blends easily with the display material.

Taking pregnancy tests and waiting for the results can put you in a nervous and anxious state. In such a situation, misreading the stick results can cause you to jump to conclusions without being fully sure of them. By knowing what do evaporation lines look like, you can take measures in understanding the results properly, and be opting for another test, too, if required.

Also Read:

False Positive Pregnancy Test
Soap Pregnancy Test
Homemade DIY Pregnancy Tests

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