What Does a Faint Line on a Pregnancy Test Mean?

Clearing Up the Confusion About At-Home Pregnancy Tests

Medically reviewed by Layan Alrahmani, MD

A faint colored line on a pregnancy test means you're pregnant. The line may be light because the urine was diluted or it's early in your pregnancy.

If you wait more than 10 minutes to check your results, you may see a colorless or gray line in the window. This is an evaporation (evap) line that appears after your urine has dried on the stick. Sometimes evaporation lines and faint positive pregnancy test lines can appear similar.

This article explains the differences between a positive pregnancy test and a result with an evap line, and reviews next steps if you think you're pregnant or are still unsure.

How Pregnancy Tests Work

At-home pregnancy tests check your urine for human chorionic gonadotropin (hCG). Your body releases this hormone when a fertilized egg implants in the lining of your uterus. An at-home test typically involves either urinating on a test stick or dipping the test stick into a cup of urine and waiting several minutes to read the results.

Depending on the test, the results may appear as a plus or minus sign, one or two lines, or the words “pregnant” or “not pregnant.”

If one line (the control line, which confirms the test is working) appears on a non-digital test, it usually means you are not pregnant. If your test shows both the control line and a colored line in the test result window, this typically indicates pregnancy.

Pregnancy tests are most accurate when taken after you have missed a period. Some at-home early pregnancy tests can be used to detect a pregnancy up to 10 days before a missed period, but these results are less reliable.

Differences Between Evaporation Lines vs. Faint Positives

An evaporation line is a faint, colorless line that appears in the results window of an at-home pregnancy test. An evaporation line may appear if you've waited too long to read the results of the test.

Sometimes evaporation lines and faint positive pregnancy test lines can appear similar, especially if you don't know exactly what you're looking for. Because of this, you may mistakenly assume that you are pregnant when you are not.

Does an evap line mean pregnancy?

An evaporation line does not indicate pregnancy. The safest bet is to take another test and read it within the specified time frame for the most accurate reading. Check with a healthcare provider if you're still unsure about the results.

Color

It's helpful to take a closer look at the line's color. Is the faint line the same shade as the control line (usually blue or pink)? This is probably a faint positive result.

If the line appears more "colorless," like gray, white, or shadowy, it's likely an evaporation line.

Thickness or Thinness of Line

Consider whether the line in question is roughly the same size as the control line. Is it the same thickness and does it run from top to bottom? If the answer to these questions is yes, even though the line may not be as dark as the control line, it's likely a faint positive.

If the line you're looking at is a different size and shape or doesn't expand across the entire length of the test window, evaporation might be to blame.

How Long It Takes to Appear

Many at-home pregnancy tests suggest reading the results within two, five, or up to 10 minutes after urinating on the stick. When urine sits on the test for too long past the recommended time, it can cause an evaporation line.

If you're checking the result and see two lines during the manufacturer's stated time frame, it's more likely to be a faint positive result. But if you wait too long after the reaction time to interpret the results (tests are meant to be read while the strip is still damp), it's probably an evap line.

How Dye Works in a Pregnancy Test

Home pregnancy tests (dye-based and digital) check your urine for human chorionic gonadotropin (hCG). The dye-based tests work by chemically reacting—and changing color—when hCG is present.

How Common Are Evaporation Lines?

Evaporation lines can be common on home pregnancy tests, but they’re not often discussed.

Cause

An evaporation line happens if the urine being tested has diluted and dried. This line can appear in the minutes after the recommended testing time has passed. This is why it's important to read your pregnancy test within the time frame noted on the product's instructions.

Getting the Most Accurate Pregnancy Test Results

When taking at-home pregnancy tests, several factors go into getting the most accurate result and avoiding confusion. Experts recommend the following tips:

• Check your results within the recommended reaction time window, which will vary slightly by pregnancy test brand.

• Try a digital at-home pregnancy test instead of a dye-based one if you're concerned about evaporation lines.

• Test first thing in the morning because your urine is more likely to have higher levels of hCG at that time.

• Though some pregnancy tests are sensitive enough to detect pregnancy earlier than a missed period, it's usually better to wait until a day after your missed period.

• Avoid drinking too much liquid before you take the test. The excess liquid can dilute the hCG levels in your urine, causing a faint line that may be difficult to read.

Takeaway

Though many pregnancy test manufacturers market their products as extremely accurate, research suggests that real-life situations (e.g., errors in the date of an expected period, certain medical conditions, or being peri- and post-menopausal) affect the accuracy rate.

Next Steps After a Faint Positive Result

You might consider retaking the at-home test to ensure the result if you think a line may be a faint positive.

After that, the next step is to check with a healthcare provider to schedule an in-office appointment. They can confirm pregnancy via ultrasound or blood test, if needed, during this visit.

Summary

An evaporation (or evap) line is a slight, typically colorless streak on an at-home pregnancy test that can cause confusion. These lines usually show up when you've read the results outside the suggested window and the urine has dried.

On the other hand, a faint positive test result will be the same color as the control line—just not as bold or dark. This is more likely to be the case if you look at the test results within the suggested time frame.

If unsure about your at-home pregnancy test results, try testing again the next day. After that, call a healthcare provider if your test is positive or if you need more help getting an accurate reading.

Read the original article on Verywell Health.