How soon after unprotected sex can I test for pregnancy?

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Created with Nataliia Yermolovych, MD, Obstetrician-Gynecologist, Ukraine

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In a nutshell

The earliest way to confirm pregnancy is with a blood test, but these are usually only performed in special circumstances. Most likely, you’ll be using an at-home urine pregnancy test. While a home test can provide accurate results as early as five days before you miss a period, most recommend waiting until after you know your period is late.

Having unprotected sex always carries the chance of getting pregnant, and you might be wondering how soon after sex you can take a pregnancy test. 

Two types of pregnancy tests exist: blood tests and urine tests. Most women use an at-home urine test to see if they’re pregnant. The outcome is pretty straightforward—a positive result means you’re pregnant, and a negative result means you’re not pregnant. 

Urine pregnancy tests can be purchased over the counter (without a prescription) from pharmacies and supermarkets or can be done by your healthcare provider. They’re cheap, accurate, easy to use, and offer a result within minutes. 

Blood tests can also be performed. These are more sensitive, as they can measure the exact level of pregnancy hormone in your body and give a positive result as early as seven days after conception. However, they are more expensive, time-consuming, invasive, and can only be done in a healthcare setting. Blood tests to see if you’re pregnant are usually only done in special circumstances, such as for women who are undergoing fertility treatment.

How early you can detect a pregnancy depends on your body and how sensitive the test is. Most at–home pregnancy tests recommend waiting until after your period is late, but some women can get a positive result up to five days before they have missed one.

How do pregnancy tests work?

Pregnancy tests work by testing for the hormone human chorionic gonadotropin (HCG). 

During ovulation, your ovaries release an egg, which can then be fertilized by a sperm cell. After it is fertilized, it will attach itself to the wall of the uterus—this is called “implantation.” Once implantation has occurred, HCG starts to be secreted. 

HCG levels double approximately every 48-72 hours in the first weeks of pregnancy, making it a convenient marker for early pregnancy detection. When HCG levels reach a certain threshold, it becomes detectable in your blood and urine.

When should you take a pregnancy test after unprotected sex?

How early you can get a positive result will depend on the day you ovulated, how long implantation took and how sensitive the test is. Here’s the timeline:

Studies have found that implantation occurs, on average, 8–10 days after ovulation—although it can occur as early as six. It then takes around three to four days after implantation for HCG levels in the urine to reach 25mIU/ml and be detectable by a pregnancy test. 

Most women will get an accurate test result if they test the day after they miss a period. However, in around 10% of women, implantation doesn’t occur until after the first day of the next expected period. This means that no matter how sensitive the test is, some women won’t get a positive test until a few days after they have missed a period.

What is the earliest day after sex I can find out if I'm pregnant?

There are many reasons why you might want to know as soon as possible if you’re pregnant. So, how many days after sex can you test? 

Whilst the average urine pregnancy test can detect levels of HCG above 25 mIU/ml, there are several “early” at–home pregnancy tests that can detect very low levels of HCG, from 6.3 mIU/ml. This means that some pregnant women could get a positive result as early as 5 days before a missed period. 

Will a pregnancy test be positive immediately after sex?

No, you will not be able to get a positive pregnancy test until several days after having unprotected sex, as it takes time for implantation to occur and for HCG levels to rise.

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What is the best time to take a pregnancy test?

Before taking a pregnancy test, you should always read the instructions first and follow them carefully.

Most tests recommend that you test with pee from your first morning’s urination, because it is the most concentrated and easier for a test to detect HCG if it’s present. 

However, if you are testing during the day or evening, try not to urinate for a few hours before the test and avoid drinking too much fluid to ensure sufficient HCG concentration.

Can you take a pregnancy test at night?

You can take a test at night, or any time of the day, but it might not be as accurate. 

Your urine is most concentrated first thing in the morning. Taking a test at night, when your urine is more watery, may mean that it can’t detect any HCG, and you can get a negative result even if you’re pregnant.

How accurate are pregnancy tests?

Many companies claim that their pregnancy tests are 99% accurate at detecting a pregnancy from the first day of a missed period. However, studies have shown that this is not always the case. 

If you have a positive test, then it is highly likely that you are pregnant. But, if you have a negative result, it’s always possible that you actually are pregnant but have tested too early. If your period doesn’t arrive, then you should repeat the test in a couple of days.

What can affect test results?

False positives

A false positive test is when the pregnancy test is positive but you’re not actually pregnant. Sometimes women going through perimenopause, menopause, or those using certain fertility drugs have a small amount of HCG present in their body that can be picked up by highly sensitive pregnancy tests. 

Occasionally, you may also have a faulty test. If you have any concerns about the result, then you should test again to double check.

There are a few other, very rare, diseases that can cause your body to produce HCG even when you’re not pregnant and result in a false positive pregnancy test, such as ovarian neoplasms. False positive results can also occur due to the presence of HCG related to tumors or recent miscarriage or abortion.

False negatives

A false negative is when the test is negative, but you are actually pregnant. These are much more common and can happen for several reasons:

  • Delayed ovulation and implantation
  • Testing too early due to inaccurately predicting when the next period is due
  • Pregnancy test not as sensitive as suggested
  • Diluted urine resulting in a lower concentration of HCG in urine

User error in taking the test or reading the result (misinterpreting a positive result as being negative)

Tips for taking a pregnancy test

  • Always read and follow the instructions included in the box.
  • Use your first morning pee for better accuracy.
  • Wait until you have missed the first day of your expected period to test.
  • If the test is negative but your period has still not started, repeat the test in a couple days.

When should you see a doctor about a possible pregnancy?

You should contact your healthcare provider as soon as you get a positive pregnancy test to discuss the next steps. 

If you want to progress with the pregnancy, then you can start reading up about what you should and shouldn’t do in pregnancy and start taking antenatal vitamins if you don’t already.

If you have had a negative pregnancy test but think you could still be pregnant, or your period has not arrived, contact your healthcare provider. They may arrange further tests.

Side-by-side comparison of urine and blood pregnancy tests, including accuracy and detection methods.

Questions from the Femia community

How accurate are home pregnancy tests compared to blood tests?

Blood tests are slightly more sensitive than urine tests, so they are useful if you urgently need to know if you’re pregnant. They also give exact HCG levels, which might be needed to track progression. However, for the majority of women, an at-home pregnancy test is good enough to confirm pregnancy.

Can stress delay my period and affect pregnancy test results?

Your period can be delayed for a number of reasons, including stress. Studies have shown that stress can cause you to ovulate later than expected and delay your next period. If ovulation is delayed, you may not get a positive result until several days after you have missed your period, because HCG levels will still be too low to be detected.

How soon after unprotected sex can I experience pregnancy symptoms?

Early pregnancy symptoms vary widely from pregnancy to pregnancy. For most women, the earliest sign is a missed period. Some women may experience other symptoms around the time they miss their period, such as feeling sick, sore breasts, or being more tired than usual.

The bottom line

Most women will get an accurate test result if they take a pregnancy test on the day they have missed their period. 

For those who find it difficult to wait that long, it is possible to get a positive result up to five days before missing your period using a highly sensitive test. However, if you take a test early and it is negative, it doesn’t necessarily mean you’re not pregnant. If your period does not arrive, then repeat the test after a couple of days to be sure.

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