What is a pregnancy test?

A pregnancy test is a way to determine if you’re pregnant by looking at the amount of human chorionic gonadotropin (hCG) in your body. From the very beginning of pregnancy, your body starts to go through changes to support growth in the grouping of cells that will develop into your baby. One thing that happens very quickly is production of hCG. This chemical is only found in pregnant women and it starts to build up once the fertilized egg implants in the uterus (womb) — about 10 days after conception.

There are two main types of pregnancy tests — urine tests and blood tests. Often, you’ll take a urine test at home with a home pregnancy test kit. This type of test can be purchased over-the-counter (you don’t need a prescription from your healthcare provider) and is available in a variety of price ranges. Blood tests to check for pregnancy are done in your healthcare provider’s office.

There are several reasons why you might take a pregnancy test. You could be trying to get pregnant and hoping for a positive result. You might have experienced an issue with your birth control. You might even be about to have a medical procedure or start a new medication that could be complicated by pregnancy. No matter what the reason, if you ever have any questions about your test results, the best thing to do is reach out to your healthcare provider. A pregnancy can also be confirmed through an ultrasound. Later in a pregnancy, an ultrasound is actually used to not only look at your baby, but make sure the timeline of development matches the dates of your conception and missed period.

How do pregnancy tests work?

When you take a pregnancy test, it’s looking for the amount of human chorionic gonadotropin (hCG) in your body. You can find hCG in your urine or blood. However, this chemical needs time to build up in your body, which can cause very early pregnancy tests to come back negative. Each day of early pregnancy, your body will create more hCG. As the weeks go on, you’ll have more and more hCG in your body, which will make it more likely that a pregnancy test will show as positive.

Pregnancy tests work by reacting to the amount of hCG in either your urine or blood. In a urine test, a piece of reactive paper detects the hCG. This might then show a plus sign, double vertical lines or even the word “pregnant.” Different tests will show a positive result in unique ways. Read the directions that come with the test to know what a positive result will look like. On the test, there will also be a control window that will show up first. Seeing a symbol in this window will tell you that the test is working. Keep in mind that different brands of tests will take different amounts of time to process.

If you take a blood test, your provider will take a sample of your blood and send it to a lab. The lab will determine the amount of hCG is in your blood.

What are the different types of pregnancy tests?

There are two main types of pregnancy tests: urine and blood tests. Urine tests are typically done at home — though you can have a urine test done at your healthcare provider’s office — while blood tests are done by your provider.

At-home pregnancy test

An at-home test usually uses your urine to look for hCG in your body. According to most manufacturers, at-home pregnancy tests are about 99% effective when used as instructed. That’s about the same accuracy rate as urine pregnancy tests done in your healthcare provider’s office. These tests are available in most pharmacies or grocery stores and they don’t need a prescription. They can take different amounts of time depending on the brand. It’s important to read the instructions on these tests before taking them.

When you go to take an at-home pregnancy test, you’ll typically place one to several drops of urine on a prepared chemical strip or place the strip in the urine stream. The strip is specially-designed to detect hCG. For many of these tests, hCG can be detected in your urine about 10 days after conception. However, taking it after your missed period reduces the chance of getting a false-negative.

There are a few things to keep in mind when you take a home pregnancy tests, including:

  • Using your first morning urine when possible. This is the time of day when your hCG levels will be the most concentrated and easily detected. If you do it at another time of day, try and make sure your urine has been in your bladder for at least four hours.
  • Not drinking excessive amounts of fluids before you take a pregnancy test. Many people think this will increase the volume of urine, but it can also dilute (thin out) your hCG levels.
  • Reading the directions that come with the test thoroughly before starting the test, and following every step precisely.

Blood test

Another type of pregnancy test that can be used is a blood test. Blood tests are rarely done because they’re expensive and tend to have the same result as a urine test. This type of pregnancy test is done using a small sample of blood that’s analyzed at a hospital or healthcare provider’s office. This blood test not only detects whether the pregnancy hormone is in your body, but can also determine how much of hormone is present.

A blood test for pregnancy might be done in special circumstances, such as for women who are having infertility treatments or when the healthcare provider thinks there might be a problem.

These blood tests are slightly more sensitive than urine tests because they can detect very small levels of hCG. That means they can provide a more accurate answer very early on in pregnancy — within nine to 12 days after conception. For this test, your blood sample is taken and sent to a lab for analysis. Results might take anywhere from a few hours to more than a day.

Your provider might also choose to use a blood test to compare hCG levels during the pregnancy. Your hCG levels usually double about every two days during the first few weeks of pregnancy. If the levels don’t rise, it might suggest a problem with the pregnancy. Extremely high hCG levels might mean that your carrying twins or that there’s an issue with the pregnancy.

When should I take a pregnancy test?

If you think you could be pregnant, it’s a good idea to take a test and make sure. If you are pregnant, you will need to begin prenatal care. Home pregnancy tests can differ in how early they’ll detect a pregnancy. In many cases, you might get a positive from an at-home test as early as 10 days after conception. For a more accurate result, wait until after you’ve missed your period to take a test. Remember, if you take a test too soon it could be negative even if you are pregnant. If you get a negative test and then miss your period, take another test or contact your healthcare provider.

What are the advantages of using a home pregnancy test?

There are quite a few advantages to using a home pregnancy test, including:

  • Pregnancy tests are inexpensive.
  • They’re easy to use.
  • Home tests provide results quickly.

According to pregnancy kit manufacturers, most at-home pregnancy tests are 97% to 99% accurate when you use them as instructed. Positive results can be trusted, but you can get a falsely negative result very early in pregnancy.

Blood tests tend to be more expensive and, for many women, the wait for an appointment can be difficult. Home tests allow you to quickly know if you’re pregnant shortly after conception.

Are all home pregnancy testing methods the same?

Most brands of at-home pregnancy tests are reliable. Although the exact testing method of different pregnancy tests can differ from one type to the other, they all look for hCG in your body. Some tests might do this through urine while others look for the pregnancy hormone in your blood. If you’re using an at-home test, most will give you the same result. The difference with your at-home tests will be the sensitivity of the test. Some might be more sensitive than others and produce a positive result — detect hCG in your urine — sooner than others. For the most accurate reading, it’s still recommended that you wait till you’ve missed your period. At that point, all tests should be accurate.

Are there any medications that can change the result of my pregnancy test?

For the most part, medications do not change your pregnancy test results. Antibiotics, birth control, alcohol and many other drugs do not impact your test results. The main reason for a false-negative is testing too early. You might also get a false-negative if you use a home test incorrectly. It’s important to follow the directions on your test kit to make sure you get an accurate result.

However, fertility drugs are one exception. These medications can sometimes cause a false-positive on your pregnancy test. If you’re taking fertility medications, reach out to your healthcare provider about your results to make sure they are accurate.

What should I do after getting a positive pregnancy test?

If you take a pregnancy test at home and it’s positive, there are a few things you should do, including:

  • Take your prenatal vitamins — pick a vitamin with folic acid included in the ingredient list. It’s recommended that you actually start taking these vitamins before becoming pregnant. This is because the folic acid can help prevent birth defects.
  • Call your healthcare provider for an appointment. This appointment might not happen for a while — sometimes several weeks — but it’s a good idea to call your provider and make the appointment.
  • Make sure to pursue healthy habits. It’s recommended that you don’t drink alcohol or smoke during pregnancy. You may also want to limit the amount of caffeine you consume each day during pregnancy.

Last reviewed by a Cleveland Clinic medical professional on 01/26/2021.

References

  • US Food and Drug Administration. Pregnancy. (https://www.fda.gov/medical-devices/home-use-tests/pregnancy) Accessed 5/7/2021.
  • US Department of Health and Human Services, Office on Women’s Health. Pregnancy tests. (https://www.womenshealth.gov/a-z-topics/pregnancy-tests) Accessed 5/7/2021.
  • Gnoth C, Johnson S. Strips of Hope: Accuracy of Home Pregnancy Tests and New Developments. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4119102/) Geburtshilfe Frauenheikd. 2014 July; 74(7): 661-669. Accessed 5/7/2021.
  • American Association for Clinical Chemistry. Pregnancy Testing Through the Ages. (https://www.aacc.org/cln/cln-industry-insights/2020/pregnancy-testing-through-the-ages) Accessed 5/7/2021.
  • American Pregnancy Association. Pregnancy Tests. (https://americanpregnancy.org/healthy-pregnancy/pregnancy-products-tests/pregnancy-tests) Accessed 5/7/2021.

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