What are Evaporation Lines on Pregnancy Tests?

Oct 22, 2013

Quick Bites:
  • Evaporation lines are colourless bands on the test kit.
  • A very common reason for evaporation lines is not adhering to the time limit.
  • For accurate results, test must be done on the day of the missed period.
  • Avoid drinking a lot of water at bedtime to keep the urine undiluted.

Evaporation lines on pregnancy tests are shadow like lines that appear in the result area of the pregnancy test kit. These faint and colourless lines develop when the sample urine in the test area begins to dry up. Evaporation lines closely resemble positive pregnancy test with only one exception that it is not as visible as the first one.

Evaporation lines Faint lines that appear because of insufficient level of pregnancy hormone (Human Chorionic Gonadotropin-HCG) are often confused with evaporation lines. However, one must conduct the test again after 72 hours for confirmation of result. An evaporation line on a pregnancy test can even make the result of the test look positive. Checking test results within the recommended time frame (as per the manufacturer’s instructions) can help in avoiding evaporation lines. Recommended time for checking the result can differ from company to company but most of them recommend a certain time duration of five minutes between the time the test is done to when the results show. The maximum time for interpreting the result is not more than 30 minutes after taking the test.


Causes of Evaporation Lines

  • The most common reason a person sees evaporation lines on the pregnancy test kit is reading it outside of the time limit that is allocated. In the urgency to check what the results show, most women remove the kit from the solution too soon. All pregnancy test kits contain instruction for the procedure as well as for interpreting the results. If you happen to check the test after the maximum time allocated on the label, it is better to do another test. Besides, the chemistry of a woman’s urine may also be responsible for why the test kit is showing evaporation lines.
  • Testing way early than when you should can make those faint lines to show up on the test strip. You must have enough hCG in your urine to ensure that the test is accurate and for that you must wait until the day you miss your period or a day or two after you have missed the period.
  • Some test kits may not be very sensitive to the hormone level and should therefore, not be bought in the first place. You can easily find test strips that are very sensitive and have a mention of it on the coverlet.
  • If you drank too much water at night before sleeping, there is a possibility that it has diluted your urine making it difficult for the test strip to catch the presence of hCG.

You may also use the other home tests that don’t use lines for testing pregnancy. Digital pregnancy test may also be used as an alternate test.

Evaporation lines can appear on any home pregnancy test kit irrespective of its brand. So, do not be unmotivated if the first few pregnancy tests do not show any accurate reading from the test. The next thing to do would be to get a blood test done.  


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