Pregnancy Tests: How Do They Work (and Which One Is Right For Me?)

When you’re needing to purchase and take a pregnancy test, it’s perfectly normal to be more than a little nervous for a lot of reasons. And if you’ve never taken a pregnancy test before, you may find yourself sitting on more concern than you need to. Fortunately, pregnancy test reliability is one area where you can put your mind somewhat at ease. Thoughts that you purchased an unreliable test or that your results aren’t going to be conclusive should not be crossing your mind right now. And the good news is that there are several varieties of pregnancy tests available both online and at the store and, if administered correctly and at the right time, any one of them are perfectly capable of giving you an accurate result.

How It Works

Pregnancy tests check a woman’s blood or urine sample for a hormone called “human chorionic gonadotropin” (hCG). This hormone is present shortly after a fertilized egg attaches to the wall of the uterus or about six days after fertilization. In the earliest stages of pregnancy, a woman’s hCG levels will roughly double every 48 to 72 hours. In a healthy pregnancy, hCG levels will continue to rise (although not as rapidly) throughout the first trimester.

Urine Testing

These are the most commonly-used pregnancy tests and can be purchased at any area drugstore or grocery store. There are many varieties available, each with their own detailed instructions, but all work in essentially the same way. Depending on the product recommendations, you’ll need to either pee on the test itself, pee into a cup and dip the test, or pee into a cup and apply a few drops with a dropper. When it comes in contact with urine, the strip on the at-home tests are designed to pick up traces of hCG. If detected, the test will typically change colors or indicate the presence in another more direct fashion (+/- or “Pregnant/Not Pregnant” for example). You’re likely to get the best reading with an early morning test as, if you are in fact pregnant, your first-morning urine will contain the highest hCG concentration. Typically a test will have a control indicator that will activate regardless of whether or not hCG is detected. If the control indicator fails to activate, the test is faulty and you should try again with a different test.

Blood Testing

Blood testing (like the kind offered by Priority Health Testing) analyzes a woman’s blood sample for traces of hCG and is slightly more accurate than at-home options. Blood tests can also detect hCG sooner than an over the counter option; around six to eight days after ovulation in most cases. There are two types of hCG tests that analyze blood samples. Qualitative tests simply test for the presence of hCG to determine whether or not a woman is pregnant (this is the service available through Priority Health Testing). Quantitative tests will actually give you an exact amount of hCG in the blood. Quantitative tests are typically done in instances of high-risk pregnancies or to confirm or rule out ectopic pregnancies or miscarriages and are not typically conducted simply as a handy alternative to qualitative blood testing or over the counter urine testing.

Are these tests accurate?

Either test is perfectly capable of giving you a result you can trust. Many at-home tests do claim to be upwards of 97% accurate with some boasting a 99% accuracy rate, but there are a lot of timing and human error variables to take into consideration. If you are pregnant and test too early, for example, your hCG levels will be too low to register and you’re likely to get an incorrect negative result. If you don’t follow the directions properly, you risk getting an inaccurate result as well. Generally, blood tests will get you a more accurate result with less of a margin for error.

Which is Better?

To answer this question, you’ll want to define what “better” means to you. As compared urine testing, blood testing is more accurate when it comes to measuring hCG levels. And since blood tests are administered in hospital or laboratory settings by professionals, the potential for misinterpreting directions or otherwise botching a test is greatly minimized. Blood testing through Priority Health Testing is extremely cost effective and convenient as well. However, if speed is your primary concern, then a trip to the local drug store for an over the counter instant testing kit may be your best bet.

When Should You Get Tested?

Keep in mind that the only way to know for sure whether or not you are pregnant is by taking a reliable pregnancy test that identifies traces of hCG in the blood or urine. There is no online quiz or anything of the sort that will give you a definitive result one way or the other. However, there are certain signs and symptoms that can indicate when it’s time to purchase a test, even before a missed period. Some of the more common signs include…

  • Swollen or tender breasts
  • Unusual spotting or cramping
  • Fatigue
  • Nausea or morning sickness (which, despite the name, can come at any time of the day)
  • Frequent Urination

Keep in mind that none of these symptoms can 100% confirm that you are pregnant. Even a missed period—typically the definitive pregnancy sign—can be caused by a change in weight, hormonal conditions, or a change in birth control. Inversely, it is possible to be pregnant and have one or two or even none of these symptoms. All that being said, taking a pregnancy test is not only the best way to know for sure if you’re pregnant…it’s the only way.

How Soon Should I Take A Pregnancy Test?

Though you’ll understandably want results much sooner, unfortunately you’ll have to wait a while after intercourse to find out whether or not you’re pregnant. Generally, the consensus on when you should take a pregnancy test is right around two weeks after intercourse or one day after your missed period. Either of these benchmarks allow for enough time for the fertilized egg to move from the fallopian tube to the uterus, implant into the uterus, and produce enough hCG to be detected by a test. Keep in mind, a blood test will be able to pick up traces of hCG sooner than an over the counter urine test.

The absolute fastest you can test would be six days after ovulation, as this is the shortest amount of time it could take for a fertilized egg to implant into the uterus. However, sperm can live inside the body for several days, so it’s impossible to say exactly when the egg will become fertilized.

What happens next?

If you have a positive blood test or urine test (and you may want to test more than once with the latter, just to be sure) then it’s time to schedule an appointment with your healthcare provider to have an ultrasound and discuss next steps for prenatal care.

If you have a negative test but still suspect you might be pregnant, try waiting a couple more days and testing again. It’s possible your body simply hasn’t yet produced enough hCG to cause a reaction. And if it ends up that you’re not pregnant, it’s still a good idea to consult with your healthcare provider for a proper diagnosis of your symptoms.