Pregnancy tests look for a special hormone —human chorionic gonadotropin (HCG) — that only develops in a person’s body during pregnancy. These tests can use either your pee or blood to look for HCG. At-home pregnancy tests that use your pee are the most common type. When used correctly, home pregnancy tests are 99% accurate.
A pregnancy test is a way to determine if you’re pregnant. If your pregnancy test is positive, it means you’re pregnant. If the test is negative, it means you aren’t pregnant. Pregnancy tests work by detecting human chorionic gonadotropin (HCG), a hormone your body makes when you’re pregnant.
From the very beginning of pregnancy, your body starts to go through changes to support the cells that will develop into your baby. One thing that happens very quickly is the production of HCG. If you’re pregnant, your body starts to produce more HCG. Your HCG levels start to build up once the fertilized egg implants in your uterus — about six to 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. This type of test is available over the counter (you don’t need a prescription from your healthcare provider) and in a variety of price ranges. Blood tests to check for pregnancy happen in your healthcare provider’s office and involve giving a sample of your blood. The other way to confirm a pregnancy is by using an ultrasound. Your provider performs an ultrasound in their 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.
Pregnancy tests look for an elevated amount of HCG. Levels of HCG rise quickly – doubling every few days in the first weeks of pregnancy. The placenta produces HCG. Only pregnant people have a placenta, which develops shortly after a fertilized egg attaches to your uterine wall.
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If you think you could be pregnant, it’s a good idea to take a test and make sure. Home pregnancy tests can differ in how early they’ll detect a pregnancy. In many cases, you might get a positive result 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’re pregnant. If you get a negative test and then miss your period, take another test.
In general, the best time is when you have your first morning pee. However, some pregnancy tests are sensitive enough to detect HCG no matter what time of day you take the test. When possible, try to wait until it’s been three hours since your last pee before you take the test. You could also take two pregnancy tests to confirm you get the same result.
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 pee or blood. HCG needs time to build up in your body. 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. This means if you take a test too soon, it will come back negative.
Pregnancy tests work by reacting to the amount of HCG in either your pee or blood. In a urine test, a piece of reactive paper detects the HCG. This test might 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. For example, most tests have a control window that shows 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 show a result.
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 in your blood. Your provider will contact you with your results.
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 your provider performs a blood test.
An at-home test uses your pee to look for HCG. They contain special strips that detect HCG. Most at-home pregnancy tests are about 99% effective when used correctly. That’s about the same accuracy rate as pregnancy tests done in your healthcare provider’s office. These tests are available in most drug or grocery stores. They’re easy to use and inexpensive. It’s important to read the instructions on these tests before taking them.
There are three ways to take an at-home pregnancy test:
For many of these tests, HCG can be detected in your urine about 10 days after conception. However, taking it after you miss your period reduces the chance of getting a false-negative result. A missed period typically happens around 14 days after conception.
There are a few things to keep in mind when you take a home pregnancy test, including:
Another type of pregnancy test 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 from a vein in your arm. This blood test not only detects whether the pregnancy hormone is in your body, but can also determine how much of the hormone is present. This is helpful for when your provider needs to know the exact amount of HCG in your blood, not just if there’s HCG in your blood.
A blood test for pregnancy might be done in special circumstances, such as for people who are having fertility 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 seven to 10 days after conception. For this test, your blood sample is taken at your provider’s office or the hospital, then sent to a lab for analysis. Results might take anywhere from a few hours to two days.
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 you’re carrying twins or that there’s an issue with the pregnancy.
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. 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 until you’ve missed your period. At that point, all tests should be accurate.
There are quite a few advantages to using a home pregnancy test, including:
According to pregnancy kit manufacturers, most at-home pregnancy tests are 98% to 99% accurate when you use them exactly as instructed. Positive results can be trusted, but you can get a false negative result if you take the test too soon.
Blood tests tend to be more expensive and inconvenient. However, blood tests can detect pregnancy sooner and are the only tests to show specific amounts of HCG in your body.
Most pregnancy tests don’t ask you to avoid activities or change your lifestyle. The only medication that may interfere with your results is fertility medication containing HCG.
Here are some helpful tips you should follow for the best results:
Each home pregnancy test is different. Read the instruction manual carefully. It will tell you how many minutes to wait for your result. In most cases, you can expect to wait three minutes for your result. Keep in mind that if you wait too long to check your result, it may be inaccurate.
Even a faint line on a pregnancy test could mean you’re pregnant. Your test will also have a control window that indicates that you took the test correctly. The instructions with your test will outline all of this. If you have any questions or remain unsure of your result after several tests, please contact your healthcare provider.
A faint line is different than an evaporation line. An evaporation line may appear if you wait too long to check your results — meaning your pee is dry. Most tests ask you to read your results before 10 minutes. This ensures the pee doesn’t dry up and you don’t get an evaporation line.
It depends on which type of test you use. Some at-home pregnancy tests may be able to detect pregnancy before you miss your period. However, if you want the most accurate result, it’s best to wait until you have missed your period.
Pregnancy tests are about 99% accurate when you use them correctly.
False results — either a false negative or a false positive — mainly happen due to using the test incorrectly. 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, such as using too much or too little pee. It’s important to follow the directions on your test kit to make sure you get an accurate result.
A false positive is rare, but it can happen. This may be the case if you experience a chemical pregnancy or lose the pregnancy shortly after the fertilized egg attaches to your uterine wall.
A blood test confirms pregnancy first because it can detect a smaller amount of HCG as compared to a test that uses your pee.
For the most part, medications don’t change your pregnancy test results. Antibiotics, pain relievers and alcohol don’t impact your test results.
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’re accurate.
If you take a pregnancy test at home and it’s positive, there are a few things you should do, including:
Yes, you’ll still have a positive result on a pregnancy test if you have an ectopic pregnancy.
A note from Cleveland Clinic
Pregnancy tests are how a person finds out if they’re pregnant. Most people take a pregnancy test at home using their pee. However, you can also take a pregnancy test at your provider’s office using a blood sample or pee. For the most accurate results, wait until you miss your period to take a home pregnancy test. If you use pregnancy tests correctly, the results are 99% accurate. Contact your healthcare provider if you have questions about the results of your pregnancy test.
Last reviewed by a Cleveland Clinic medical professional on 11/28/2022.
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