How soon will a pregnancy test read positive?

If you think you might be pregnant, it’s natural to want a clear answer as soon as possible. Sitting with the uncertainty of the two-week wait can be tough: You’re not alone if you’re struggling with not knowing. Equally, you may be afraid of taking a test too early and getting an inaccurate result, which can mess with your emotions.

So, what’s the earliest you can take a test and feel confident that it’ll be accurate? We’ll explain the facts with advice from Flo expert Dr. Jenna Flanagan, obstetrician and gynecologist, US.

Key takeaways: How soon will a pregnancy test read positive?

• At-home pregnancy tests work by looking for the pregnancy hormone human chorionic gonadotropin (or hCG) in your pee. Some claim to pick up pregnancy earlier than others, and that has to do with how sensitive they are to hCG.
• Many at-home pregnancy tests can read positive 10 days after you conceive. Confusingly, that’s not always the exact moment you had sex. Instead, it's the moment the sperm meets the egg, which happens when your egg is released (ovulation). These tests will have an hCG sensitivity of 25 mIU/mL.
• Some at-home tests promise to be more sensitive than this, claiming to detect levels of hCG as low as 6.3 mIU/mL. These tests could read positive as early as six days before your missed period (or five days before your period is expected). 
• Ultra-sensitive tests may be more likely to show inaccurate results — or false negatives — if taken as early as suggested. 
• After you have missed a period (roughly 14 days past ovulation), all tests should be accurate. To figure out when this day lands for you, try tracking your cycle with a period-tracking app like Flo. 

How soon will a pregnancy test read positive? 

Many at-home pregnancy tests can read positive as early as four days before your period is due, and some are even more sensitive than this (meaning they may be able to pick up a pregnancy even earlier). So, when to take a pregnancy test depends on the type of test you’re taking. 

At-home pregnancy tests work by detecting the level of pregnancy hormone in your urine. Called human chorionic gonadotropin, or hCG, this hormone starts to be released only after the fertilized egg implants in your body. Implantation happens from around six to 10 days after ovulation. However, it takes some time for hCG to build up to detectable levels. So, even though many tests could read positive four days before your period is due, or even sooner, experts often recommend waiting a few days longer than this. 

“The general rule is to wait until the first day of your next period when it is missed, as the hCG levels will then be high enough to detect,” says Dr. Flanagan. 

If you’re wondering how soon after unprotected sex you can test for pregnancy, that’s not always easy to say. The general rule is to take a test around 14 days after conception, but conception doesn’t always happen immediately after you have sex. Sperm can live inside you for up to five days, waiting for an egg to be released, so it’s better to test 14 days after you think you ovulated instead. You can use an ovulation-tracking app like Flo to become familiar with your body’s ovulation signs.

“Tests that claim they can detect a positive [result] earlier aren’t less accurate,” explains Dr. Flanagan. “But as the hCG levels are quite low, there is a higher chance of getting a false negative result.” She continues: “This is when you are pregnant, but the [hCG] levels are too low to be detected by the test.” 

For example, one brand claims its most sensitive test can detect pregnancy five days before your expected period. However, it explains that the test can only detect 79% of pregnancies this early, compared to more than 99% if you were to take it on the day of your missed period. 

Waiting to test may give you a more definite result, but that doesn’t mean it’s easy to be that patient. Known as the “two-week wait,” many of us struggle with this period of uncertainty. One Flo member sums it up perfectly on the app’s Secret Chats space: “I mean, no [big deal],” they write. “I only want to know if my life is about to change fundamentally and forever.” 

Meanwhile, another person shares how they can’t help obsessing over possible symptoms. “Seven days past ovulation now,” they write. “I’ve had so many random moments where I thought I was [pregnant], but now I’m not sure. I feel like I’m going crazy!!”

They explain that their strategy is to test early and often. “I’m going to test at 10 days past ovulation knowing it will probably be negative and then each day until my period. The biggest thing I’ve learned so far is to be kind to myself.”

Maybe, like this Flo member, an early test will feel worth it for you too, even if it means retesting a few days later. Or perhaps you’d rather wait for a more certain result. There’s no right or wrong here: It’s about what feels best for you. 

If there’s one thing for sure, it’s that trying to get pregnant involves becoming a lot more organized with your cycle dates. First, you need to know when to time sex to overlap with your fertile window, and then you need to figure out the best day to take a pregnancy test. You can use our pregnancy test calculator to get an estimate of when to take a test or sign up for the app for a more accurate prediction. The Flo app can also help you understand your body’s fertility signals so you can time conception sex more confidently.

How do pregnancy tests work?

Let’s recap the science. Your body starts producing the hormone hCG after implantation, which is when a fertilized egg attaches to the lining of your uterus. This is also the moment you officially become pregnant. 

After implantation, your rapidly dividing cells start to form what will become your baby, as well as an important organ called the placenta. The placenta starts producing hormones — including hCG — to signal to your body that you are pregnant and to pause your periods. 

As hCG only exists in your body in significant amounts during pregnancy, testing for this hormone will reveal whether or not you are pregnant. The thing is that hCG takes a little while to build up — levels rise quickly after implantation, doubling every two to three days. Once levels are high enough, that’s when the hormone can be picked up in either your urine or a blood test. 

You can test for hCG using an at-home pregnancy test. This involves peeing directly onto a detection stick or collecting your urine in a cup first. Different tests will present your results in different ways, so make sure you read the instructions carefully. For example, line tests may display a positive result as double vertical lines. Meanwhile, digital tests usually show the words “pregnant” or “not pregnant” — potentially leaving less room for confusion. 

Pregnancy blood tests, on the other hand, need to be carried out by a health care professional. Blood tests are slightly more sensitive than urine tests and can detect pregnancy as early as seven days after conception (or seven days before a missed period). They can also tell you exactly how much hCG you have in your body. 

While some health care teams may be able to give you the result within a few hours, it could take two days to get the result. Plus, given that accurate urine pregnancy tests are available over the counter, many people find that at-home tests are the most convenient way to test for pregnancy. 

Comparing home pregnancy test brands and detection timelines

You’ll likely find several brands of pregnancy tests at the drugstore and even more online. With various products claiming different timelines, choosing a test can be a little overwhelming. 

As we’ve seen, the timeline for when a test can pick up a pregnancy is determined by how sensitive it is to hCG. You should be able to find information about your test’s hCG sensitivity in the instructions pamphlet. But what does it mean in practice? A 2014 study of home pregnancy tests found that tests sensitive to hCG levels of 25 mIU/ml can pick up a pregnancy up to four days before your expected period. That’s around 10 days after you conceived. 

Here are some products claiming to have an hCG sensitivity level of 25 mIU/mL:

• MomMed Pregnancy Test Strips (25 mIU/ml)
• Easy@Home Pregnancy Test Strips (25 mIU/ml)
• Clinical Guard Pregnancy Test Strips (25 mIU/ml)
• One Step Pregnancy Test (25 mIU/ml)
• Accufast Pregnancy Test with Week Indicator (25 mIU/ml)

Meanwhile, other tests claim they can detect pregnancy as early as five days before you expect your period to arrive. These products have an hCG sensitivity level of less than 10 mIU/ml and include:

• First Response™ Early Result Pregnancy Test (6.3 mIU/mL) 
• Wondfo Ultra Early Pregnancy Test Strips (10 mIU/mL)
• Clearblue® Digital Ultra Early Pregnancy Test (10 mIU/ml)
• Preview Pregnancy Test Strips (10 mIU/ml)
• DiaSpot Rapid One-Step Test Strip (10 mIU/ml)

Please note that these lists are not exhaustive by any means, and we don’t endorse any particular brands. Instead, Flo aims to independently compare the facts to help you make an informed choice.

Can a pregnancy test give a false negative or false positive?

If you take them correctly, most at-home pregnancy tests are 99% accurate. But there are circumstances when you may get a false result. 

False negatives: What causes them?

A false negative is when a test says you are not pregnant, but you actually are. One study by the Washington University School of Medicine suggested that around 5% of pregnancy tests deliver a false negative result. 

Our dedicated page has everything you need to know on false negative pregnancy tests. But in short, these can be caused by: 

• Taking the test too early in your cycle. Our pregnancy test calculator is a useful tool to help you choose the right time to test. 
• Checking the test results before the instructions tell you to. You need to make sure it’s had enough time to detect any hCG in your urine.
• Taking the test later in the day when your urine isn’t concentrated enough. For the most accurate results, it’s best to take the test right after you get up in the morning. Find out other tips on what not to do before taking a pregnancy test in our handy guide. 

False positives: What causes them?

A false positive pregnancy test result is rare, but it can happen. It’s when you get a positive test result, but you’re not actually pregnant. These can be caused by: 

• Taking a pregnancy test soon after taking fertility medication containing hCG. There’s a chance the test could pick up the hCG from the drugs, not due to a pregnancy.
• Health conditions, such as those affecting the ovaries. “There are also cases where some tumors or cancers secrete an hCG-like molecule that is detected as a positive on a test, but these are rare,” adds Dr. Flanagan.
• Using the test incorrectly. “One common cause of a false positive with line tests is when people leave the pregnancy test out for too long and a second dry line [also known as an evaporation line] appears,” says Dr. Flanagan. So don’t forget to keep an eye on the clock. 
• Having a pregnancy loss soon after implantation. This is known as a chemical pregnancy and happens when an embryo stops growing before it would be picked up on an ultrasound scan, in the very early weeks of pregnancy. Technically, chemical pregnancies aren’t false positives, as the pregnancy was real. Some people don't like the term chemical pregnancy for this reason, as it can sound like it dismisses the fact it was a real pregnancy. 

Pregnancy loss can affect people in many different ways, but any kind of loss can be heartbreaking — no matter how early it happens. If you’re struggling with pregnancy loss or anxiety about pregnancy, please know that you’re not alone. Our crisis page can help you find support in your local area. 

What to do if your pregnancy test is negative, but you have symptoms

It can feel incredibly confusing and frustrating to be experiencing early signs of pregnancy but testing negative, especially if you’re finding it hard to get pregnant. “A second test should be [taken], as the first test could have expired or been damaged,” says Dr. Flanagan. “If worrisome symptoms exist after a few negative tests, it’s a good idea [to speak to your doctor] to confirm the negative test and then evaluate the possible causes for the symptoms.”

It can feel like a cruel fact, but there is some overlap between pregnancy symptoms and plain old pre-period symptoms. “Not all pregnancy symptoms are related to pregnancy and can be part of the menstrual cycle with hormonal fluctuations,” says Dr. Flanagan. For example, tiredness, bloating, and breast tenderness can all crop up right before your period as well as during early pregnancy.   

The timing of your cycle could give you some clues as to what’s going on. “When someone is truly feeling pregnancy ‘symptoms,’ it’s typically at 6 weeks pregnant when the hCG level is sufficiently high,” says Dr. Flanagan. “HCG rising to high levels is one of the triggers of nausea and vomiting.” 

Tracking your cycle and ovulation with Flo can help you figure out if it could be pregnancy symptoms or not. You can also speak to others going through similar things via our safe Secret Chats space in the Flo app. Wondering whether or not you might be pregnant can sometimes feel oddly lonely. But, as Secret Chats reveals, many others are going through it alongside you.