1. Getting pregnant
  2. Trying to conceive
  3. Pregnancy tests

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What Causes False-Negative Pregnancy Tests?

When it’s time to take a pregnancy test, your emotions may be running high. Some women strongly suspect that they’re pregnant but then get a negative test result. If you’re sure you’re pregnant, but your test was negative, then read on. We’ve outlined the different ways your test could have gotten messed up.

Before the 1970s, there was no way women could tell if they were pregnant without the help of a doctor. At-home pregnancy tests weren’t invented until 1976.

The technology used in these tests has improved significantly since then. When used correctly, they are almost 99 percent accurate. If you’re attempting to use an at-home pregnancy test, read the directions carefully and follow them closely. Any skipped steps or timing issues can give you the wrong results. 

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The test strip is designed to track the levels of human chorionic gonadotropin (hCG) in your urine. HCG is a hormone that’s created in your body once a fertilized egg implants in the uterus (or outside the uterus in case of an ectopic pregnancy). Your body only produces this hormone if you’re pregnant (the production of the hormone by some cancerous tumors is the only exception). HCG doubles roughly every 48 hours, but this isn't the case for everyone — you can use our online hCG calculator to track your hCG levels at home.

To get the most accurate results, follow these steps:

  • Take the pregnancy test on the first day of your missed period. If you’re pregnant, your placenta will have started to produce hCG by this point, and the hormone will be present in your urine.
  • Take the test first thing in the morning. Your hCG levels will be at their highest in the morning, so you have a greater chance of them being detected by the test.
  • Don’t drink too much. Don’t drink to make yourself pee in the morning. Extra fluids can dilute your hGC levels and cause your test to fail.

Each test has different “positive” and “negative” indicators, so read your package carefully to make sure you know what the various results mean. Some common results for “pregnant” are:

  • A smiley face
  • A pink line
  • A blue line
  • The word “pregnant”

Some women get a negative result only to find out later from their doctor that they are, in fact, pregnant. There are a few reasons why the test may not read your hCG correctly.

If you got a negative reading from a pregnancy test but later learned that you were pregnant, how did the test get it wrong? What causes false-negative pregnancy tests? There are a few ways that the test could read your urine wrong. 

If you don’t follow the directions on the package, the pregnancy test will not be set up properly to test your urine. 

Each test is different and comes with different directions. You may have missed a step or performed the test incorrectly. 

If you’re getting a false-negative pregnancy result consistently and you’re sure that you’re pregnant, go to the doctor. They use a similar pregnancy test, but they’re used to the variables and can have more accurate results. 

Your hCG won’t be high enough to detect until six days after conception

If you took the test too early, then the test will read negative even if you are pregnant. The test is fine-tuned to detect low amounts of hCG, but there aren’t enough hormones to be detected on the test until about a week after conception. 

It’s a good idea to wait until the first day of your missed period to take a pregnancy test. Once your hCG levels are high enough, your period should stop. That means it’s been at least six days since conception, and the test should read positive if you’re pregnant. 

You have to be sure about the timing of the first day of your period. Many women have irregular periods, or don’t track them, and may get the day wrong.

When you track your periods, you can get to know your cycle. It has its own ebbs and flows, but you can learn the basics, like the typical length of your cycle. If you know your cycle, you can tell with more accuracy when you missed the first day. On average, a normal cycle is between 21 and 35 days.

Some women take a pregnancy test just before their period is supposed to start, when hCG levels are too low to be detected. 

Diluting your hCG levels can also give you a false-negative pregnancy result.

If you’re preparing to take a pregnancy test, it’s best to take it first thing in the morning. Some women drink water or other fluids early in the morning or late at night in order to be able to pee in the morning for the test. 

Diluting the urine can spread out the presence of hCG and make it too low for the test to read, giving you a false reading. 

Conversely, if your hCG levels are too high, your pregnancy test can also return a false-negative. This is called a “hook effect.” It’s very rare, but it does happen.

Pregnancy tests are designed to track a specific range of hCG in the body. If you have too little, (if you took the test too early or diluted your urine), it won’t be detected. If you have too much, (if you took the test too late), the test strip may not be able to bond to any of the molecules, possibly showing a negative result.

If you’ve gotten a negative pregnancy test but haven’t had your period, is something else causing your period to be late?

There are a handful of reasons (other than pregnancy) why you might miss a period, such as:

  • Hormonal disorders (e.g., thyroid dysfunction, high prolactin, polycystic ovary syndrome)
  • Too high or too low body weight
  • Some chronic diseases
  • Illness
  • Travel
  • Poor sleep
  • High stress
  • Excessive exercise

If these explanations don’t apply to you, visit the doctor to get a second pregnancy test. They use a blood test, which is more accurate and can detect lower levels of hCG than a home pregnancy test can. 

When it comes to pregnancy tests, follow the directions and know your cycle. If you’ve followed the directions closely and know your cycle well, you should get accurate results. However, if you suspect you’re pregnant and are still getting false-negative pregnancy test results, then go to your doctor. They can determine for certain whether you’re pregnant or if you’ve missed your period for some other reason.