What Is a Pregnancy Test?

Blood or urine tests measure a hormone produced in pregnancy

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A pregnancy test is a way to determine if you’re pregnant by using a urine test stick at home or giving a blood sample at a doctor’s office. You can buy an over-the-counter (OTC) pregnancy test at a pharmacy or grocery store or get a free pregnancy test at your local health department, community health center, or Planned Parenthood. 

Pregnancy tests check your urine or blood for human chorionic gonadotropin (HCG), a hormone your body releases when a fertilized egg attaches to the lining of your uterus, marking the beginning of pregnancy about six days after conception.

Typically, a positive result means you’re pregnant. A negative result means you’re not. However, interpreting your results can be complicated depending on when exactly you take a pregnancy test.

Pregnancy test

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Whether you’re trying to conceive or hoping you're not pregnant, taking a pregnancy test can be a highly emotional and nerve-wracking experience.

If you’re new to this, a few questions are likely at top of mind: How accurate are at-home pregnancy tests? When exactly can you take one for the most reliable results? Does a plus sign always mean you’re pregnant, or could you have a false positive?

If you think you might be pregnant, you should take a test. While a missed period is the most common signal that you've become pregnant, you may also experience other early signs of pregnancy including fatigue, sore breasts, a frequent need to pee, nausea, bloating, cramps, or very light spotting (a.k.a. “implantation spotting”).  

Sound familiar? Read on to learn everything you need to know about pregnancy tests, including different types to consider, how to time yours for the most accurate results, and what to do next.

Types

The two main types of pregnancy tests are urine tests and blood tests. In most cases, a urine test will suffice to tell you whether or not you're pregnant. But your doctor may order blood tests if you may have a health condition or symptoms that could indicate problems with a potential pregnancy.

Urine Tests

Urine tests can be done at home with an OTC kit or at your healthcare provider’s office. Typically, you either pee on the end of a dipstick or dip it into a cup of collected urine. A few minutes after that, the dipstick shows your test result on a strip or screen: a plus or minus sign, one or two lines, or the words “pregnant” or “not pregnant.” 

Follow the label instructions for how long to wait before you view your result, as this can vary depending on the type of pregnancy test.

Blood Tests

Blood pregnancy tests, on the other hand, can only be done at a doctor’s office or testing lab. Typically, doctors opt for urine tests similar to those you’d buy over the counter for patients who may be pregnant.

However, they could order blood tests if you have a higher-risk pregnancy, are doing fertility treatments, or are concerned that you may be having multiples or a miscarriage, or other complications such as an ectopic or tubal pregnancy. 

For a blood test, your healthcare provider will draw a blood tube to be sent to a laboratory for testing. The blood drawing process typically takes less than five minutes, and you might feel a little prick of the needle going in or out. It could take a few hours to over a day to receive your results. 

While it takes longer to get results compared to a urine test, a blood test can detect a pregnancy earlier (about 10 days after conception, compared to 2 weeks or more for a urine test). 

Your doctor may use one or both types of blood tests: 

  • A qualitative HCG blood test can tell you whether HCG is present with about the same accuracy as a urine test. 
  • A quantitative blood test (a.k.a. beta HCG test) measures exactly how much HCG is in your blood. 

Timing

If you suspect you’re pregnant, the typical advice is to take a pregnancy test as soon as possible, but there are downsides to taking one too early. For the most accurate results, when you should take a test depends on what type of test you’re using and how well you know your menstrual cycle. 

Some OTC early pregnancy tests are sensitive enough to tell you if you’re pregnant four to five days before you miss your period.

However, the majority of at-home pregnancy tests will not show that you’re pregnant until the date of your expected next period (or when you know that it’s late). If you take a pregnancy test before this, your results may be inaccurate. 

Generally, the earliest you’d want to take a pregnancy test for accurate results is after the first day of your missed period. Keep in mind that it’s easy to make miscalculations at this point, though. The first day of your period can vary quite a bit from month to month, especially if you have a history of irregular periods. 

For the most trustworthy results with an at-home pregnancy kit, test one to two weeks after missing your period. If you have irregular periods, don’t get periods, or haven't been charting your cycles, you may want to wait until three weeks after having unprotected sex for the most accurate results.

Because the ideal time to take a pregnancy test varies depending on the specific type of test, read the label to figure out exactly how early you can take yours for accurate results.

Since your HCG levels are higher when your urine is more concentrated, it’s best to take a test first thing in the morning or when you haven’t urinated for several hours. 

If you get a negative result but suspect that you’re pregnant, you can take a test again in a couple of days. Because your HCG levels go up fast in a normal pregnancy—doubling every few days—you may get a positive test later. If you don’t but still think you may be pregnant, call your doctor. 

If you get a positive result, contact your healthcare provider to schedule an appointment to confirm the results and talk about the best next steps for you. 

Accuracy

When it comes to pregnancy tests, accuracy is of the utmost importance. Although many at-home pregnancy tests claim to be “99% accurate,” they may be less accurate depending on how you use them or just how sensitive they are.

For example, if you take a pregnancy test too early, you could get a false-negative result because your body isn’t producing enough HCG yet. 

What’s more: “Too early” may have a different meaning for you, as up to 10% of people don’t experience implantation—and a corresponding surge in HCG—until after the first day of their missed period. This means while one pregnant person might get a positive result as soon as day 1 of their missed period, another might not. 

To ensure you get the most accurate results, check the expiration date, follow the label instructions carefully, take the test after a missed period, and be sure to do it when you haven’t urinated in a long time. 

Even if the line or plus sign is thin, if it’s visible, you’re probably pregnant. This may indicate that your HCG levels are low because you’re early in your pregnancy. 

False Negative and Positive Pregnancy Tests

Unfortunately, sometimes pregnancy test results aren’t accurate. It’s possible to get a result that says you’re not pregnant when you are (a false negative) or that you’re pregnant when you aren’t (a false positive). 

You may have a false negative result if you take a pregnancy test too early, the test is defective, or you have problems with the pregnancy. A false positive result can happen if the pregnancy test doesn’t work correctly or detects HCG in your urine or blood for another reason.

For example, HCG may show up if you take the test shortly after taking fertility drugs that contain HCG, such as Pregnyl or Profasi.

All in all, the most common reason for a misleading pregnancy test is taking it too early before your HCG levels have risen.

A Word From Verywell

Whether you get positive, negative, or mixed results, contact a doctor or midwife if you believe you may be pregnant. It's completely normal to feel a slew of different emotions at this point, from joy and excitement to fear and dread. But the sooner you can confirm the results, the sooner you can begin to figure out what path forward makes the most sense for you.

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Article Sources
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  1. Cleveland Clinic. Pregnancy test information. Updated June 21, 2017.

  2. Office on Women's Health. U.S. Department of Health and Human Services. Pregnancy tests. January 2019.

  3. Planned Parenthood Federation of American. Pregnancy tests. 2021.

  4. Food and Drug Administration. Pregnancy. Updated April 29, 2019.

  5. Gnoth C, Johnson S. Strips of hope: Accuracy of home pregnancy tests and new developments. Geburtshilfe Frauenheilkd. 2014;74(7):661-669. doi:10.1055/s-0034-1368589