Pregnancy test: evaporation line

The evaporation line does not signal pregnancy. It often occurs if you are checking the test result too late or if you have performed the test incorrectly. When it appears it is best to run another test.

When we speak of an evaporation line, we refer to one or more more or less marked lines which appear due to the fact that the urine which has deposited on the stick is drying.

But let’s go in order.

Some pregnancy test kits are designed to produce two straight lines: one line for the control, and another line for the actual test.

  • The control line always appears after a successful test.
  • The test line,  on the other hand, appears only when you are pregnant.

If you’re not familiar with these types of tests, you might think you’re pregnant when you see two lines. However, the simultaneous appearance of two lines does not necessarily mean that you are pregnant: the second line could in fact be a simple evaporation line, therefore not indicative of an ongoing pregnancy.

To distinguish between a positive line and an evaporation line, you have to keep in mind,

  1. that evaporation is the passage of a liquid into a gaseous state,
  2. that the evaporation line displays urine drying
  3. the evaporation line is colorless

So when you take a pregnancy test , to get an accurate result check the result within the time period indicated on the package, and if by any chance an evaporation line appears it is better to do another test to get an accurate result.

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform,

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