Decoding Pregnancy Tests: Does Line Thickness Mean Anything?

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By Jessica Solloway | Updated on Jan 4, 2024
Image for article Decoding Pregnancy Tests: Does Line Thickness Mean Anything?

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After a few years of navigating a pandemic, we’re all experts at decoding the results of at-home Covid tests. While there's room for error, the color of the test line correlates with how much virus is in the body, with a darker hue likely signaling a higher viral load. But whether that tell-tale line is faint or dark, we know any shade of pink indicates a positive result thanks to the high accuracy rate of FDA-authorized tests. Yep, consider it a signal to hunker down for some binge-watching.

But decades before1  there was Covid, another at-home test provided the OG line reveal: the pregnancy test. Instead of detecting proteins in a virus, this test measures the hormone human chorionic gonadotropin (hCG) in your urine. Similar to a Covid-19 test, the dye-based pregnancy test displays a line or a plus/minus sign that provides information on what’s going on in your body and whether or not you might be pregnant. (Just remind yourself how cool science is when you’re trying to gracefully pee on a stick.)

This test may seem straightforward until you are anxiously trying to decode your results and find your mind racing with questions. What if the line is fuzzy or faint? Does it mean something different than a thick, bold line? Is it possible to get a false positive or negative? 

There’s plenty of room to feel bewildered, but we’ve got you covered.

The FYI on HCG 

First, let’s take a moment for a quick flashback to sex-ed class. 

When an egg is fertilized, it makes its way to the uterus to implant in the uterine wall. Implantation of the embryo triggers the placenta to form and begin producing hCG. Known as the pregnancy hormone, hCG works alongside estrogen and progesterone to signal the body to stop releasing eggs, thicken the uterine lining, and support a growing baby.

According to the Cleveland Clinic3 , hCG is found in your urine or blood about 10-11 days after conception. While pregnancy tests are most accurate after you’ve missed your period, some highly sensitive at-home pregnancy tests may be able to tell if you’re pregnant even before then since small amounts of the hormone are present as early as 10 days. As your pregnancy progresses, hCG levels rise quickly (almost doubling every three days) through the first 8-10 weeks of pregnancy. Then, they’ll gradually decline during the remainder of the 40 weeks. 

Timing Is Everything 

The strength of the positive test result comes down to the amount of hCG in your urine. A positive pregnancy test taken after a missed period very likely means you’re pregnant. Taking a test early in your pregnancy (especially before your missed period) could result in a faint line, as the test may not clock as much hCG in your body. In a nutshell: the more hCG in your body, the stronger and more visible the positive line will be. 

Whether the line is faint or bold, a pink line usually indicates you are pregnant. While uncommon, keep in mind that it is possible to get a positive result even if you’re not pregnant. A false positive4  can happen for a variety of reasons5 , including using an expired test, having hCG in your body due to recently taking fertility drugs that contain the hormone, an ectopic pregnancy (when a pregnancy grows outside of your uterus), or miscarriage. That’s why it’s always a good idea to take a second test and check in with your doctor once you see those two pink lines. 

On the flip slide, no pink line means you are not pregnant, but there is a catch here, too. If you took the test just a few days after possible conception, you can get a false negative as the hCG levels might not be high enough to be detected yet. In that case, wait a few days and test again. 

Tips for Taking a Pregnancy Test 

Home pregnancy tests are intended to be quick, easy, and reliable. To get an accurate result, follow these helpful tips: 

  • Wait to take a test until after you’ve missed your period. 

  • Take a pregnancy test first thing in the morning since that’s when urine is the most concentrated. 

  • Avoid drinking a large amount of fluids2  before taking a test as this could dilute your urine/hCG levels and cause a faint line or a false negative.

  • Check the test’s expiration date. The results may not be accurate if it’s expired. 

  • Follow the manufacturer’s directions carefully to avoid any issues when taking the test. There’s always the possibility of user error. 

  • Make sure you understand how to read the results. Some tests show a plus or minus sign, others show one or two lines that are either pink or blue. 

  • Don’t be fooled by the evaporation line or “evap line.” After taking a test, the urine sample will eventually dry up and evaporate from the results window, creating a very faint, colorless streak. So, if you take a peek at the stick beyond the window of time the manufacturer advises, you could see this very subtle line. This is not a positive result. 

The Bottom Line on Pregnancy Test Lines

No matter which brand of pregnancy test you’re using, one of the simplest ways to get accurate results is to take another test and compare them. If you think you’re pregnant, you should also visit your healthcare provider. They’ll perform a quantitative blood test to measure the exact amount of hCG present in your blood. This is the most precise way to confirm your pregnancy and provide more details on its progression. 

Whether you have possible Covid sniffles or suspected pregnancy morning sickness—there’s no need to read between the lines. Getting answers from an at-home test provides peace of mind and makes the next steps easier to navigate. 

Pregnant woman holding her stomach on a bed with a plant in the background

Want evidence-based health & wellness advice for fertility, pregnancy, and postpartum delivered to your inbox?

Your privacy is important to us. By subscribing you agree to our Privacy Policy and Terms & Conditions.

Expectful uses only high-quality sources, including academic research institutions, medical associations, and subject matter experts.

  1. National Institutes of Health"The Thin Blue Line: The History of the Pregnancy Test"https://history.nih.gov/display/history/Pregnancy+Test+-+A+Thin+Blue+Line+The+History+of+the+Pregnancy+Test#:~:text=The%20answer%20to%20this%20age,drug%20store%20shelves%20that%20year..

  2. Danielle Betz; Kathleen Fane"Human Chorionic Gonadotropin"StatPearls PublishingAug 14, 2023https://www.ncbi.nlm.nih.gov/books/NBK532950/#:~:text=Human%20chorionic%20gonadotropin%20is%20a,the%20liver%2C%20and%20the%20colon..

  3. Cleveland Clinic"Human Chorionic Gonadotropin"https://my.clevelandclinic.org/health/articles/22489-human-chorionic-gonadotropin.

  4. Mayo Clinic Staff"Home pregnancy tests: Can you trust the results? "https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/home-pregnancy-tests/art-20047940.

  5. Cleveland Clinic"Causes of a False Positive Pregnancy Test"Oct 18, 2021https://health.clevelandclinic.org/false-positive-pregnancy-test.


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Updated on Jan 4, 2024

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Decoding Pregnancy Tests: Does Line Thickness Mean Anything?

 Jessica Solloway Profile Photo
By Jessica Solloway | Updated on Jan 4, 2024
Image for article Decoding Pregnancy Tests: Does Line Thickness Mean Anything?

After a few years of navigating a pandemic, we’re all experts at decoding the results of at-home Covid tests. While there's room for error, the color of the test line correlates with how much virus is in the body, with a darker hue likely signaling a higher viral load. But whether that tell-tale line is faint or dark, we know any shade of pink indicates a positive result thanks to the high accuracy rate of FDA-authorized tests. Yep, consider it a signal to hunker down for some binge-watching.

But decades before1  there was Covid, another at-home test provided the OG line reveal: the pregnancy test. Instead of detecting proteins in a virus, this test measures the hormone human chorionic gonadotropin (hCG) in your urine. Similar to a Covid-19 test, the dye-based pregnancy test displays a line or a plus/minus sign that provides information on what’s going on in your body and whether or not you might be pregnant. (Just remind yourself how cool science is when you’re trying to gracefully pee on a stick.)

This test may seem straightforward until you are anxiously trying to decode your results and find your mind racing with questions. What if the line is fuzzy or faint? Does it mean something different than a thick, bold line? Is it possible to get a false positive or negative? 

There’s plenty of room to feel bewildered, but we’ve got you covered.

The FYI on HCG 

First, let’s take a moment for a quick flashback to sex-ed class. 

When an egg is fertilized, it makes its way to the uterus to implant in the uterine wall. Implantation of the embryo triggers the placenta to form and begin producing hCG. Known as the pregnancy hormone, hCG works alongside estrogen and progesterone to signal the body to stop releasing eggs, thicken the uterine lining, and support a growing baby.

According to the Cleveland Clinic3 , hCG is found in your urine or blood about 10-11 days after conception. While pregnancy tests are most accurate after you’ve missed your period, some highly sensitive at-home pregnancy tests may be able to tell if you’re pregnant even before then since small amounts of the hormone are present as early as 10 days. As your pregnancy progresses, hCG levels rise quickly (almost doubling every three days) through the first 8-10 weeks of pregnancy. Then, they’ll gradually decline during the remainder of the 40 weeks. 

Timing Is Everything 

The strength of the positive test result comes down to the amount of hCG in your urine. A positive pregnancy test taken after a missed period very likely means you’re pregnant. Taking a test early in your pregnancy (especially before your missed period) could result in a faint line, as the test may not clock as much hCG in your body. In a nutshell: the more hCG in your body, the stronger and more visible the positive line will be. 

Whether the line is faint or bold, a pink line usually indicates you are pregnant. While uncommon, keep in mind that it is possible to get a positive result even if you’re not pregnant. A false positive4  can happen for a variety of reasons5 , including using an expired test, having hCG in your body due to recently taking fertility drugs that contain the hormone, an ectopic pregnancy (when a pregnancy grows outside of your uterus), or miscarriage. That’s why it’s always a good idea to take a second test and check in with your doctor once you see those two pink lines. 

On the flip slide, no pink line means you are not pregnant, but there is a catch here, too. If you took the test just a few days after possible conception, you can get a false negative as the hCG levels might not be high enough to be detected yet. In that case, wait a few days and test again. 

Tips for Taking a Pregnancy Test 

Home pregnancy tests are intended to be quick, easy, and reliable. To get an accurate result, follow these helpful tips: 

  • Wait to take a test until after you’ve missed your period. 

  • Take a pregnancy test first thing in the morning since that’s when urine is the most concentrated. 

  • Avoid drinking a large amount of fluids2  before taking a test as this could dilute your urine/hCG levels and cause a faint line or a false negative.

  • Check the test’s expiration date. The results may not be accurate if it’s expired. 

  • Follow the manufacturer’s directions carefully to avoid any issues when taking the test. There’s always the possibility of user error. 

  • Make sure you understand how to read the results. Some tests show a plus or minus sign, others show one or two lines that are either pink or blue. 

  • Don’t be fooled by the evaporation line or “evap line.” After taking a test, the urine sample will eventually dry up and evaporate from the results window, creating a very faint, colorless streak. So, if you take a peek at the stick beyond the window of time the manufacturer advises, you could see this very subtle line. This is not a positive result. 

The Bottom Line on Pregnancy Test Lines

No matter which brand of pregnancy test you’re using, one of the simplest ways to get accurate results is to take another test and compare them. If you think you’re pregnant, you should also visit your healthcare provider. They’ll perform a quantitative blood test to measure the exact amount of hCG present in your blood. This is the most precise way to confirm your pregnancy and provide more details on its progression. 

Whether you have possible Covid sniffles or suspected pregnancy morning sickness—there’s no need to read between the lines. Getting answers from an at-home test provides peace of mind and makes the next steps easier to navigate. 

Pregnant woman holding her stomach on a bed with a plant in the background

Want evidence-based health & wellness advice for fertility, pregnancy, and postpartum delivered to your inbox?

Your privacy is important to us. By subscribing you agree to our Privacy Policy and Terms & Conditions.

Expectful uses only high-quality sources, including academic research institutions, medical associations, and subject matter experts.

  1. National Institutes of Health"The Thin Blue Line: The History of the Pregnancy Test"https://history.nih.gov/display/history/Pregnancy+Test+-+A+Thin+Blue+Line+The+History+of+the+Pregnancy+Test#:~:text=The%20answer%20to%20this%20age,drug%20store%20shelves%20that%20year..

  2. Danielle Betz; Kathleen Fane"Human Chorionic Gonadotropin"StatPearls PublishingAug 14, 2023https://www.ncbi.nlm.nih.gov/books/NBK532950/#:~:text=Human%20chorionic%20gonadotropin%20is%20a,the%20liver%2C%20and%20the%20colon..

  3. Cleveland Clinic"Human Chorionic Gonadotropin"https://my.clevelandclinic.org/health/articles/22489-human-chorionic-gonadotropin.

  4. Mayo Clinic Staff"Home pregnancy tests: Can you trust the results? "https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/home-pregnancy-tests/art-20047940.

  5. Cleveland Clinic"Causes of a False Positive Pregnancy Test"Oct 18, 2021https://health.clevelandclinic.org/false-positive-pregnancy-test.


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