How Soon After Unprotected Sex Can You Test for Pregnancy?

Medically reviewed by Renita White, MD

Whether you're actively trying to get pregnant or not, the time between unprotected sex and when you can take a pregnancy test feels like forever. But if you test too soon, you risk getting a false-negative result, meaning you're pregnant but the test shows you're not.

The right time to take a pregnancy test after having unprotected sex is the first day after a missed period or 21 days after unprotected sex if you have irregular periods.

This article will explain why it's important to wait and how to take a pregnancy test for accurate results.

When to Take a Pregnancy Test

The best time to take a pregnancy test is the first day after a missed period or 21 days after unprotected sex. Some tests claim they can detect a pregnancy a few days before a missed period, but you may get inaccurate results.

It takes just minutes after unprotected sex for the sperm to reach and fertilize the egg. Then, it will take several more days for the fertilized egg to travel to the uterus and implant itself in the uterine lining. It can take two to three weeks from when you have unprotected sex to when you are officially pregnant.

What If It's Been Less Than 5 Days Since You Had Sex?

Taking a pregnancy test less than five days after having unprotected sex is too soon.

Pregnancy tests measure the amount of human chorionic gonadotropin (HCG) in urine, a hormone that doesn't begin production until the embryo implants itself into the uterus. Levels of HCG are lowest in early pregnancy and increase by 50% daily for the first ten weeks of pregnancy.

An early test may not detect low HCG levels before a missed period, potentially producing a false negative result.  

Timing Testing Around Your Periods

If you know when your next period is due, wait until you are late to take a pregnancy test. Pregnancy is one of the potential causes of a missed period. Usually, it is the very first sign of pregnancy. The result of a pregnancy test is also more likely to be accurate when you take it after a missed period.

Knowing when your next period is due can be trickier if you have irregular periods. If you’re unsure when your next period will arrive, take a pregnancy test three weeks after you had unprotected sex.

How (and When) to Take a Pregnancy Test

The pregnancy hormone, HCG, can be found in the urine and in the blood. At-home pregnancy tests use urine, while blood tests can only be taken at your healthcare provider's office or another medical center.

At-home pregnancy tests are a solid option because they are easy to use, inexpensive, and convenient. You’ll have your results in a matter of minutes. At-home pregnancy tests can be found at most drugstores, discount stores, online, and in the family planning sections at grocery stores.

At-home pregnancy tests require peeing on a stick with a test strip inside it, or they may use a paper strip that you would dip into a clean cup containing your urine. You must follow the instructions exactly, no matter what brand or type of at-home pregnancy test you use. If the test has expired, get a new test.

At-home pregnancy tests are 99% accurate when used correctly. Here are some tips to avoid false positives, which occur when the test reads positive but you're actually not pregnant:

• Make sure you take the test after you miss your period. If you don’t know when your period is due, take the test 21 days after you have had unprotected sex.

• Take the test using your first pee of the day. Any HCG levels will be most concentrated at this time. If you need to take it later in the day, make sure it has been at least 3 hours since you last peed.

• Avoid drinking too much water before taking the test. This will dilute HCG, risking a false-positive result.

Pregnancy Tests: Blood vs. Urine

There is no difference in accuracy between blood and urine tests for pregnancy if taken after a missed period. However, blood tests are more sensitive before a missed period and can detect HCG to confirm pregnancy at that time. Unless your healthcare provider tells you one is needed, a blood test is unnecessary to confirm a pregnancy.

What to Do About Your Pregnancy Test Results

Assuming you have taken the pregnancy test after a missed period and followed instructions correctly, you are not pregnant if the results are negative. If your results are positive, it's safe to assume that you are pregnant.

Make an appointment with a healthcare provider to confirm the pregnancy and get a physical examination. If this was a planned pregnancy, you may be happy but still overwhelmed with the news. An unplanned pregnancy will be more complicated. You can discuss next steps with your healthcare provider and a counselor.

Related: What Is a False Positive Pregnancy Test?

Summary

If you have had unprotected sex and you think you may be pregnant, you need to know as soon as possible. At-home pregnancy tests are inexpensive and can be found at most drug and grocery stores.

The best time to take a pregnancy test is first thing in the morning, after a missed period. If you don’t know when your period is due, you’ll need to take the test three weeks after you had unprotected sex. Regardless of your results, discuss next steps with a healthcare provider. 

Read the original article on Verywell Health.