Can Your Birth Control Interfere with Pregnancy Test Results?

Medically reviewed by Nicole Galan, RN on February 3, 2016Written by Kimberly Holland on February 3, 2016

Birth control pills are 99 percent effective in preventing pregnancy if taken correctly. That’s an exceptionally high success rate, but it isn’t 100 percent. You could still get pregnant. For that reason, you may want to take a pregnancy test from time to time if you’re sexually active. The hormones in your birth control pills won’t affect a test’s outcome, but there are a few things you should keep in mind if you’re on the pill and taking pregnancy tests.

What Birth Control Pills Do

Birth control pills are designed to prevent pregnancy in three key ways. First, the pill stops a woman’s monthly ovulation. Ovulation is the release of a mature egg. If that egg meets a sperm, a woman can become pregnant.

Second, birth control pills make the lining of the cervix difficult for sperm to penetrate. Specifically, the cervix develops thick, sticky mucus. Sperm have great difficulty getting past this mucus, which reduces your chances of becoming pregnant.

Some birth control pills also affect the lining of your uterus. The hormones in birth control pills thin the lining. This makes it difficult for a fertilized egg to attach. Without that lining, you may also not have a period or any bleeding. This may be mistaken for a pregnancy, which is just one of the reasons you could suspect you’re pregnant even though you’re taking the pill properly.

How to Take the Pill Properly

“Perfect use” requires a woman to take the pill every single day at the same time without skipping a dose or being late on starting a new pill pack. When taken perfectly, birth control pills are 99 percent effective in preventing pregnancy. However, most women don’t take birth control pills in this manner.

“Typical use” refers to the way most women take the pill. That may mean you’re several hours late or miss a dose or two in any given month. In this case, the pill is only 91 percent effective in preventing pregnancy.

Aiming for perfect use can help increase the effectiveness of this birth control method. Once you’re in the habit of taking your pill at the same time every day, it’s important to maintain this routine. You can do this by taking all of the pills in your pack, including the placebo pills. In most pill packs, placebo pills have little to no active ingredients. Keeping your daily routine going can also ensure that you don’t accidentally forget to start your next pack.

If you do skip or miss a dose, play it safe and use backup protection, such as a condom, for at least a week. If you went more than a day or two without a dose, it might be safer to use a backup method for up to a month.

Symptoms of Pregnancy

The earliest symptoms of pregnancy can be easy to miss. If you notice any of these symptoms, take a pregnancy test to find out your status:

  • Morning sickness, which can occur any time of day, may be one of the first signs of pregnancy. It involves nausea or vomiting and it can begin within a few weeks of conception.
  • Early pregnancy hormonal changes may leave your breasts feeling tender and sore. They may also swell or feel heavier.A missed period is often the first sign of pregnancy for many women. If you’re on birth control, you may not get regular periods, so a missed period may be hard to determine.
  • Changes to your body in early pregnancy may leave you feeling tired and sluggish more easily.
  • Urinating more than usual may be a sign of pregnancy.
  • Suddenly developing food aversions may be a sign of early pregnancy. Food cravings can be, too. The hormones in birth control pills can also change your eating patterns, so it may be hard to determine what’s causing your sudden palate shift.

Why Is My Period Late?

Taking a Pregnancy Test

Over-the-counter pregnancy tests detect the level of a hormone called human chorionic gonadotropin (hCG). Pregnancy tests can detect this hormone 99 percent of the time if used correctly. To ensure you get the most accurate result possible, you should do the following:

  • Follow the test’s instructions. Each test is different, so before you open the package, be sure to read the instructions. Keep a timer handy if you need to time your test.
  • Wait for the right time to take the test. Your hCG levels will begin to climb once the fertilized egg is implanted. For some women, this may not be until the first day of your period. If you can wait until after your missed period, tests may be more accurate.
  • Take the test in the morning. Your levels of hCG will be highest after you wake up because you haven’t urinated yet.
  • Research the tests you get. Some pregnancy tests tout that they can detect a pregnancy days before you miss a period. These tests are more sensitive than more traditional tests. Which test you use may affect how soon you can know if you’re pregnant.

What Can Cause an Incorrect Result?

Though pregnancy tests are highly accurate, there’s still room for error. A few issues can affect your results, but your birth control pill isn’t one of them. The hormones in your birth control pill don’t affect a test’s ability to detect hCG.

Possible issues do include:

Reading the Test Incorrectly

Differentiating between two faint blue lines and only one may be difficult. This is especially true if your levels of hCG are very low and the test isn’t very sensitive to the hormone. Wait a few days and test again if you think your result was difficult to read.

Using the Test Incorrectly

Although each test comes with very specific instructions, it’s possible that an error was made during testing. For example, some tests give results in as few as two minutes, but the results aren’t valid after 10 minutes. This is because the results might change due to the test’s design. Other tests require you wait at least 10 minutes for a result. Not knowing how your test functions could lead to an inaccurate result.

Using an Expired Test

Don’t risk a false test result by using an expired test. Once the “use by” date has passed, pitch the sticks and buy new ones.

Taking the Test Too Soon

Your levels of hCG will increase quickly once a fertilized egg is in place. If you take your test too soon, the hormone levels may not be high enough yet for a test to detect. It’s recommended that you wait until you’ve missed your period to take the test.

Picking the Wrong Test for Your Needs

If you want to test for a possible pregnancy before your missed period, you should pick a test that’s designed to test that early. The test will have to be very sensitive to get an accurate result. If you use a more traditional test before your missed period, the test may not be able to detect the hormone.

How to Confirm Your Pregnancy Status

While at-home urine pregnancy tests are very accurate, they aren’t 100 percent accurate. Blood tests done by your doctor are 100 percent accurate, however. If you want further confirmation of your pregnancy status, make an appointment with your doctor. They’ll draw a quick blood sample and send it for testing. In some cases, you can know within a matter of minutes whether you’re pregnant or not. Otherwise, you may have to wait two to three days for your results to return.

Outlook

You can and should take pregnancy tests while you’re on birth control if you want to know your pregnancy status. If you become pregnant, it’s good to know as soon as possible. Knowing early allows you to better prepare for what comes next.

If you decide to continue with your pregnancy, this allows you to stop taking the pill and start taking measures to help your baby grow. If you decide to terminate your pregnancy, knowing sooner rather than later enables you to take the proper steps.

Talking with Your Doctor

If you’re unsure whether you should take a pregnancy test, always err on the side of caution. Take one if it will help you reduce your anxiety.

You can also talk with your doctor about signs and symptoms that may indicate the need for a pregnancy test. Some of the earliest symptoms of pregnancy can go undetected. Your doctor may give you more specific symptoms to look for before you take a test.

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