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Can Birth Control Affect Pregnancy Test Results?

Can Birth Control Affect Pregnancy Test Results?

  • Catherine Poslusny
    Reviewed By: Julie Lamonoff, CNM, OBGYN-NP, Shannon DeVita DNP, FNP-BC, CPNP-PC
    Updated:

If you're on birth control, taking a pregnancy test is probably the last thing you want to worry about. Unfortunately, taking hormonal birth control isn't always a perfect process. With inconsistent use, there may be a slight chance you could get pregnant while on it.

Here, we'll break down everything you need to know about taking a pregnancy test while on birth control, including if birth control can affect pregnancy test results.

Short answer: Can birth control affect pregnancy tests?

Pills and other types of hormonal birth control contain two hormones: progestin and estrogen. Pregnancy tests measure a completely different hormone, called human chorionic gonadotropin (hCG). So you can be reassured that the hormones in birth control will not affect your pregnancy test results.

Your birth control won't affect the results of a pregnancy test, but it doesn't mean you won't ever need to worry about getting pregnant while on them. Every form of contraception (except abstinence, or not having intercourse) comes with a slight risk of getting pregnant, though that chance is higher with some methods of birth control than others.

If you're worried you may be pregnant, don't ignore your concerns simply because you're on birth control. Home pregnancy tests can help you figure out whether those symptoms you're experiencing are signs of early pregnancy or just premenstrual syndrome (PMS).

For best results, you should wait to take the test until the first day after you're expecting your period to come. That's when hCG levels should be high enough for a test to detect. While your body always produces small amounts of hCG, it increases when you first become pregnant.

If your birth control makes it hard to tell when your menstrual cycles start and end (think: irregular or absent periods), wait at least four weeks after having sex to take the test.

Can you get pregnant while on birth control?

Though very unlikely, it is possible to get pregnant while you're on birth control. When used consistently, hormonal birth control uses some combination of estrogen and progestin to keep you from getting pregnant. It does this by:

  • Preventing ovulation: When you're not on hormonal birth control, one of your ovaries will usually release an egg each cycle. If this egg is fertilized with sperm, it can lead to a pregnancy. If you don't release an egg, you won't get pregnant.

  • Affecting your cervical mucus: Cervical mucus (CM) is a natural substance made by your cervix. You've probably noticed it as a clear or white discharge on your underwear between periods. Some birth control can make this CM thicker, preventing sperm from successfully reaching the egg.

  • Making it harder for implantation to happen: After an egg is fertilized, it needs to implant in your uterine lining for you to get pregnant. Some hormonal birth control can lower your risk of pregnancy by making the uterine lining thinner, causing a fertilized egg to have a harder time attaching.

How well your birth control works to prevent pregnancy is measured by perfect use and typical use. Perfect use means you follow the directions exactly all the time, something that for many can be hard to actually achieve. Typical use generally looks more like normal life:

  • Skipping a daily birth control pill or taking it late

  • Being late in replacing your birth control ring or patch

  • Waiting too long to get your next birth control shot

  • Taking expired birth control pills

With perfect use, hormonal birth control pills are 99.7% effective. With typical use, they're about 91% effective, meaning that 9 out of 100 women may get pregnant while on the pill. Here's how that compares to other types of birth control:

Method Effectiveness (typical use) Effectiveness (perfect use)
Pill 91% 99.7%
Ring 91% 99.7%
Patch 91% 99.7%
Shot 94% 99.8%
Hormonal IUD 99.8% 99.8%
Copper IUD 99.2% 99.4%
Implantable rod 99.95% 99.95%

A note about hormonal birth control and periods:

If you're worried you may be pregnant, getting your period every month can make you breathe a sigh of relief. But a missed period isn't always cause for concern. It's normal for some forms of birth control to cause you to have irregular or missed periods.

Plus, when on birth control, your period isn't technically a real period because menstrual bleeding only happens after ovulation. If you haven't ovulated that month, you'll have withdrawal bleeding instead. This happens during the placebo pill week for the pill or the break week in between applying the patch and can feel very similar to a regular period.

When can you take a pregnancy test when on birth control?

The guidelines for when to take a pregnancy test are the same, whether you're on hormonal birth control or not. This is because pregnancy hormone tests look for hCG, and hormonal birth control has no effect on hCG levels. This is true for all forms of hormonal birth control, including the pill, patch, shot, ring, and IUDs.

For the most reliable results, it's best to wait to take an over-the-counter pregnancy test 1-2 weeks after the first day of your missed period. Taking it too soon could lead to a false negative because hCG hasn't had enough time to build up to detectable levels in your body.

So what are you supposed to do if you don't have regular periods? You'll want to make sure it's been at least two weeks after you've had sex. This is the earliest a pregnancy test can detect hCG from a pregnancy. If your test is negative, you should wait a week and take another test to make sure.

Note: If it's been less than five days since you had under-protected or unprotected sex, it's not too late to take emergency contraception.

What are the symptoms of pregnancy, even on birth control?

Symptoms of pregnancy shouldn't be affected by whether you're on birth control or not. Though you may not have a missed period to look out for, you can still watch for these signs of pregnancy while you're waiting to take a pregnancy test:

  • Swollen or tender breasts

  • Nausea and/or vomiting

  • Fatigue

  • Having to urinate more often

  • Spotting (not as heavy as period bleeding)

  • Bloating

  • Cramps

  • Mood changes

  • Taste and smell changes for certain foods

Waiting to take a pregnancy test or analyzing early pregnancy symptoms can be nerve-wracking. Pregnancy symptoms are different for everyone, and it's possible to have these symptoms and not be pregnant. But you could also be pregnant and not have these symptoms.

Long story short, symptoms alone can't tell you if you're pregnant. The most reliable way to know for sure is to take an hCG pregnancy test.

How to take a pregnancy test

You'll probably see two types of home pregnancy tests: strips and sticks. You'll either pee directly on the stick, or you'll first pee in a cup and dip strip or stick into it.

Before you take your test, make sure to read all the instructions on the box. It should tell you everything you need to know about how to take the test, how long to wait before you look at the results, and how to figure out if you have a positive or negative test.

After you get your test result, whether it's positive or negative, you may want to take the test again if you aren't sure it's accurate. If your test was negative, you should wait a few days and take another test. If your test was positive, you may want to schedule an appointment with your health care provider. They'll give you a urine or blood test to check your hCG levels and confirm your results.

What can throw off a pregnancy test?

We keep talking about taking multiple tests or seeing a doctor to confirm your results because there are a few things that can change the accuracy of home pregnancy tests.

Home pregnancy tests are 99% effective, but they're not perfect. Some situations that can lead to a false positive or negative include:

  • Taking the test too early, before hCG levels show up

  • Using an expired test

  • Taking a test in the afternoon or evening with diluted urine. The best time to take an at-home pregnancy test is in the morning before you've had anything to drink.

  • Recent miscarriage or termination

  • Menopause

  • Ovarian problems

Takeaways: Can birth control affect pregnancy test results?

While there are a handful of things that can cause a false positive or negative result on a pregnancy test, birth control isn't one of them. The hormones estrogen and progestin in your birth control aren't the same as the hCG hormone that a pregnancy test detects. So you never have to worry about your birth control standing between you and accurate pregnancy test results.

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