How Soon Can a Blood Test Detect Pregnancy?

Updated on March 13, 2018
Expert ReviewedDr. Mark Trolice, Director of Fertility Care
NathaNater profile image

Nathan has two daughters. When he and his wife were trying to have a baby, they did considerable research on issues concerning pregnancy.

How Early Can a Blood Test Detect Pregnancy Hormones?

"Pregnancy blood tests are reliably able to detect pregnancy at much lower ranges of circulating pregnancy hormone in the blood and thus can catch a pregnancy in its very early stages," says Dr. Cindy M. Duke, a physician with the Nevada Fertility Institute in Las Vegas. "Circulating levels of pregnancy hormone would have to be much higher in order for it to be detected in the urine (home pregnancy test)."

Do you think you might be pregnant, but you are not sure about the reliability of the home test you've taken? Or perhaps you want to know now if you're pregnant but it's too early to take a urine test, so you are considering a blood test.

When can you trust the home test and when do you need to take a blood test instead?

There is much to consider when deciding whether or not to get the blood test. How accurate are they? How much trouble and cost are they? How soon can you take one and when will you get the results?

Let's explore.


What Is an hCG Blood Pregnancy Test?

There are two types of blood tests to determine pregnancy:

  • Qualitative hCG blood serum tests check to see if a hormone called human chorionic gonadotropin is present in your blood. HCG is a hormone produced by the body during pregnancy. A positive result means you are pregnant and a negative result means you are not pregnant.
  • Quantitative hCG blood serum tests also check to see if hCG is present in your blood, but these tests can detect even trace amounts of the hormone. Because it is more precise, this test helps to determine whether the pregnancy is normal and healthy.

How Early Can a Blood Test Tell Me I'm Pregnant?

"The earliest a blood test can detect hCG is approximately 8-10 days post-ovulation," says Dr. Mark Trolice, Director of Fertility Care at the IVF Center in Winter Park, Florida. "What makes things more challenging? A woman who has irregular menstrual periods and does not know when she ovulated."

Both qualitative and quantitative hCG blood serum tests can accurately detect pregnancy 8-10 days after ovulation (about a week before your period is due). This is an advantage to taking the blood test: You can take it sooner than the urine test.

How Accurate Are Blood Pregnancy Tests?

The blood test for hCG is the most accurate to detect a pregnancy, says Dr. Mark Trolice.

Blood tests have a 99% accuracy rate, so they are almost always accurate. The main reason for this is that the quantitative test can detect even the smallest traces of the pregnancy hormone hCG. However, hormone levels can vary from one woman to another.

"The range of normal beta hCG levels is very wide," says Dr. Serena Chen, a fertility expert at the Institute for Reproductive Medicine and Science at Saint Barnabas Medical Center in Livingston, New Jersey, "so it's important to have the help of your doctor to interpret test results."

How Long Do You Have to Wait for the Results of a Blood Test?

So you've gone to the doctor's office, waited to be seen, and had your blood drawn. Of course, it's not over.

Your blood has to be sent to a lab to be analyzed. How long it takes for them to give you the results varies from lab to lab. It could take an hour or several days. A couple of days is a typical waiting period for lab results.

How Accurate Are Urine Pregnancy Tests?

Comparatively, urine tests, or home tests, can be inaccurate 6% of the time. They are more accurate when taken no earlier than seven days after a missed period. Taking a home pregnancy test too soon can produce an inaccurate result.

Have you tried a home pregnancy test or a blood test?

See results

Pregnancy Blood vs. Urine Tests

Blood tests:

  • are more expensive than home urine tests
  • have to be given at a doctor's office
  • can be done just one week after ovulation
  • can take up to 48 hours to produce a result
  • are more accurate than urine tests.

Urine tests:

  • are convenient and private
  • are less expensive
  • produces results in minutes
  • are only accurate when done seven days after a missed period
  • produce more false positive results than blood tests.

Using Blood Tests to Diagnose Ectopic or Tubal Pregnancy

"An early ectopic pregnancy may yield a false negative if you test too early," says Dr. Chen. If you have concerns about the possibility of ectopic pregnancy, discuss them with your doctor.

Ectopic pregnancies are fertilized eggs that have implanted in the fallopian tube instead of the uterus. This type of pregnancy can present similar symptoms as a normal pregnancy but can be life-threatening for the woman.

A quantitative hCG blood test can help diagnose (or rule out) an ectopic pregnancy. They are more precise than qualitative tests and detect lower levels of hCG in the blood. In an ectopic pregnancy, hCG levels are usually lower than in a normally developing pregnancy and also rises at a slower-than-normal rate.

While an ultrasound exam may be necessary to confirm the diagnosis, the blood test can be done earlier, which is important given the risks of this type of pregnancy.

False Positive Results of Blood Pregnancy Test

False positive results of pregnancy blood tests are rare, but they do happen. Some conditions can lead to a result of pregnancy when the woman is, in fact, not pregnant.

Because blood tests detect the presence of the hormone hCG, any level of hCG—even if it is there for another reason—could lead to a false positive test result. Some non-pregnancy reasons for hCG to be in the blood are:

  1. Biochemical pregnancy, or a pregnancy that is lost before the woman even knew she was pregnant.
  2. Pituitary hCG, or hormones created by the pituitary gland that are similar to hCG. It is possible for women to have low levels of hCG in the blood and not be pregnant.
  3. Antibodies that interfere with hCG tests and lead to elevated hormone levels.

What Is Phantom hCG?

Phantom hCG is a false positive pregnancy blood test.

In these cases, the blood test for hCG cross-reacts with non-pregnancy related proteins in the blood called heterophile antibodies.

"When this occurs, it can actually have serious consequences unless your physician is aware of this false positive risk," says Dr. Mark Trolice. "What are the risks? Ectopic pregnancy, where an embryo implants outside the uterus. This is a potentially life-threatening event but is often conservatively treated using an injection of the chemotherapy agent, methotrexate."

But if the blood test for hCG is a false positive, and there is, in fact, no ectopic pregnancy, the woman may be needlessly exposed to repeated injections of methotrexate with risks of serious side effects from this medicine.

Another condition that can lead to a false positive, says Dr. Trolice, is gestation trophoblastic disease, or cancer of pregnancy tissue. In this scenario, persistent low levels of phantom hCG can be misinterpreted for this disease resulting in aggressive but unnecessary medical intervention.

How to avoid over-treating a false positive hCG test? The urine pregnancy test, because heterophile antibodies are not present in urine.

Can Blood Pregnancy Tests Give False Negative Results?

If you have had a pregnancy blood test and it came back negative, but you feel pregnant, it is possible that you really aren't pregnant. Many of the symptoms of an approaching period (nausea, fatigue, crampiness, breast tenderness) can be confused with pregnancy.

Is It Possible to Take a Pregnancy Blood Test Too Early?

Yes. In rare cases, it takes longer than usual for hCG hormone levels to build up in the blood. If you had a negative blood test result but you really feel pregnant, wait a few days and get tested again.


So as you can see, there are many things to consider when you are trying to figure out whether to take the blood test and what to expect from it. It is more expensive and less convenient. You will have to wait for the lab to get results. However, it is more accurate, can detect the slightest bit of pregnancy hormone in your blood, and you can test sooner than you can with a urine test.

Expert Review

Dr. Mark Trolice

Director of Fertility Care
The IVF Center
Winter Park, Florida
  • The article has been modified since this review was written.

Questions & Answers

    © 2014 NathaNater


      0 of 8192 characters used
      Post Comment

      • profile image

        Rae 6 weeks ago

        Thanks for this artical. Was looking for a simple answer to how early blood hCG test can detect pregnancy but couldn’t stop reading! It was so interesting and informative. I have questions answered that I didn’t even know I had!

      • profile image

        Stella 2 months ago

        I had my last period on 25th of February,sex on 13th of march and 20, have not see my period, done blood test on 23rd of march but negative. What could be the problem.

      • profile image

        haseena 2 months ago

        1st i missed period so i take pregnency test how many days to take

      • profile image

        larissa 2 months ago

        So my last period was feb 11. I took a pregnancy test negative on march 12. I am getting heart burn and cramping since march 1st but no period. Been nausea since then too. What day can i get a blood test and what day can i take another pregnancy test to see if i can get a postive

      • profile image

        Marissa Henderson 2 months ago

        Hi so Feb 11 I had my peroid and Friday and monday i got to pregnancy blood tests done and they both didn't change they both said less then 2.4 I need to know what to do next im suppose to start my period March 11 I need advice

      • profile image

        Emily 2 months ago

        So I had my period last in January on the 24th and had intercourse everyday until the 4th of last month and from the 16 until the 2 of this month and I still haven't had my period but spotted for 4 days light . could I be pregnant now?

      • profile image

        rossy 3 months ago

        From November I m not having my periods regularly last month I had unprotected sex with my partner I have tested after 10days of intimacy it shows negative?? Still I get pregnant????

      • profile image

        Ann 3 months ago

        I havent seen my period for like 2days now i went for a blood pregnancy test and it showed negative but my period hasnt come still...What will i do?

      • profile image

        Katie 4 months ago

        I take a pregnancy test at home and the doctor it came back povsitive

        But the doctor did a blood test and it came back negative.

      • profile image

        JENN 4 months ago


      • profile image

        Samvia munir 5 months ago

        My serum test positive what I do

      • profile image

        glory 6 months ago

        i had unsafe sex 4days after my period,my man pulled out

        now my period is little late and i took urine test twice its positive but am positive that i had no sperm in my V during last sex!i be feeling PMS syndromes for almost 2weeks

        i doubt these tests

        QUESTION....hCG can be detected few days before period???

      • profile image

        Star 6 months ago

        I had blood test done to get my birth control shot started up cause i was a month late and had sex two days previous to blood test. Ive been really nauseous lately is there a chance i could be pregnant

      • profile image

        i am Helen i got pregnant for 5 days carried out blood test but still negative 7 months ago

        I am Helen I got pregnant for 5 days I carried out blood test but still negative

      • profile image

        Lori ward 7 months ago

        I am wondering if I can be pregnant because I took a test and it was negative and I had some light blood and then spoting and then light blood and the spoting again and now nothing is it to soon to take a blood test please let me know

      • profile image

        Xxxx 8 months ago

        I had my last period May 8th 17, i've had spotting twice, still not had a period, i've done about 8 home pregnancy tests all negative, the doctor has done 2 negative pregnancy tests, i've now been sent for bloods to be done i'm awaiting results. My stomache is bulging now from the top of my stomache, my waist is disappearing and i'm constantly tired and want to eat loads! I just needs to know if i am pregnant cos something is wrong?

      • profile image

        Mary 8 months ago

        Hi, I had my periods on 23rd of August 2017,had unprotected sex on 28th of the same month and on 2nd of September, I then took emergency pills on 3rd of September and had unprotected sex again the same day after taking the pills.

        What are the possibilities, please help. Can I be pregnant?

        My periods are not regular.

      • profile image

        Special Kay 8 months ago

        I had intercourse on the 21st, 22nd, and the 28th of August. My period was due to come on the 29th of August, but did not show. I waited until August 30th to take a test and it was instantly positive! I took a second one later in the day and it was also positive. Is it possible to have a positive test so soon?

      • profile image

        Kayla 8 months ago

        I had sex on August the 7th. I then had a blood pregnancy test done with qualities/quantitative serum done on August 13th and got a negative result. If the result were positive would it had of shown up?

      • profile image

        Xmen 11 months ago

        My Gf is scared whether she is pregnant..her period is almost 2 months late. So we did a normal blood test.. Report is not coming yet.. So I want to know if it can tell if she is pregnant or not??

      • profile image

        DONT KNOW ANYMORE 12 months ago

        HI THERE


      • profile image

        Peanut 12 months ago

        My wife has been spotting for a few days a light red and today she says honey why is it a lil darker that with a lil blood clot, I said I have know idea, so I googled it and it said, if she is pregnant then it's the 1st trimester of being pregnant and don't be scared,she did go and get a blood test like a day ago or so, just waiting to hear back from the doctor's office

      • profile image

        Larissa 13 months ago

        Hi I went through an iui cycle through ivf I had the trigger and also pregnyl 3 times after getting inseminated I then got my 2 week pregnancy test she said my levels were at 9 so she can't so I'm not pregnant because 5 and under means ur not pregnant but she thinks that my levels might b up a bit cause if the medication I was on. Has anyone has this please let me know

      • profile image

        Annabel 15 months ago

        My Implannon was in 5 years too long. I had a slight 2-3 day period before Christmas. Before that I was regular 28 days bar one month before the 2-3 days I bled for 3wks. it's now February nd still no period I'm worried the 2-3 days was a show. Done a test two wks ago which was negetive iv had a blood test not checking for pregnancy nd the nurse said nothing. What's going on could I be pregnant?

      • profile image

        emmza 20 months ago

        hi im 31 years old i not sure if im pregnant i took urine test thats came negative a couple took are from dollar store 1 i took today was a u check from the dollar store and on august the 8 took a clear blue test digtial came negative on 10th took another clear blue negative still havent got my period my period doesnt come regular so not sure but in july period was july 8 and last period was August 5 to august 11 was i even ovualting? back to this part ok had sex august 14 start spotting august 19 a bit pink more red light with a bit brown 1 time i wipe was a chuck of red blood but just one time not even sure if i was ovulating still no period and its september 14 today again period is not regular took a blood pregancy test on sept 15 negative is it still early still no period ? was I even ovualting?

      • profile image

        lexie 20 months ago

        so I'm 20 and i suspected i was pregnant, i did 2 drugstore tests which were negative (it was too early) and i went to the gynecologist today, she did a vaginal ultrasound and told me i seemed to be pregnant (that there was a lot of fluid which there usually is early in a pregnancy) so she sent me to do a blood test but it came out negative. i'm very confused, i haven't gotten my period yet, could i be pregnant even though the test was negative? I'm only 2 days late on my period and the interaction happen at the 10th of August. Any help anyone? I though i would wait until I'm 7-8 days late and then go to an other gynecologist. could i be pregnant or..? can anyone help me out? i know that blood tests aren't too reliable when it's that early in a pregnancy because you dont have enough of that hormone in your blood yet right? :/ please help I'm stressing out

      • profile image

        Pequena 2 years ago

        I been feeling pregnant for about 2 months now. Symptoms: sore breasts, areolas darkened with small bumps, leakage when nipples are squeezed, dizziness, nauseas, no appetite, visible veins (arms, legs, breasts), headaches, tiredness, bloading, metallic taste, moodiness. Had bleeding lime periods for the passed 2 months. Had urine test and blood work done which all were negative. Saw the doctor and did blood work and tested my prolactin levels and my thyroid, also checked my pituitary gland for anedoma and everything is normal. I'm still having all the symptoms and I don't know what else to do or think. Can anyone help please

      • profile image

        Neha 2 years ago

        I am 22 years old, and a pcos patient!

        I had sex with my boyfriend on 1st jan 2016, I had an ipill after that!

        But we had unprotected sex again ! I googled and chose not to eat ipill again!

        How can I be sure of not being pregnant? Do I need to take a pregnancy test?

      • profile image

        elizabeth 2 years ago

        am 10 days to my menses,can blood test detect if am pregnant?please any help

      • profile image

        Jenn 2 years ago

        Hi i had a question about blood test and pregnancy is it true that sometimes it wont even show then until about a month to two months i ask cause my last period was in aug. And i still havent had my period i had a blood test done an it was negitive is why im asking

      • profile image

        Carlota 2 years ago

        Hi im 4 days late iv taken 2 hpt both negative im having a little dizziness lately and been having cramps should I go get a blood pregnancy test ??

      • profile image

        Ivone 2 years ago

        Can hCG be detected 3 days after ovulation? Is the 7 to 12 days after ovulation pretty accurate, as in cannot be detected sooner? I had a vaginal ultrasound and doc couldn't tell if i was pregnant so she had me take a blood test, which came back negative. I ovulated around Tuesday (i took the home test) and had intercourse days leading up to ovulation. That's why i ask :)

      • profile image

        Chrissy 2 years ago

        I have taken 3 tests 10 dpo 13 dpo and 14 dpo and all negative i had intercourse last thursday and started to spot on friday and mow its monday an i have still been only spotting some pink some brown som blood red and a few times with clots. We have not taken any more HPT im nervous and scared to .... My question is can it be my period if im only spotting and there is no blood flow.

      • profile image

        vicky 2 years ago

        Hi im 10 weeks late with pcos...ive done pregnancy tests n come back negative....I had a hormone blood test last week and got a borderline result today...Iive gotta wait for phone consultation tomorrow to find out what it means.....could it mean im pregnant? As ive been trying for over a year.....

      • profile image

        laurice 3 years ago

        Scared, I am older and now I am 9 days late. Scared because I have always wanted children. I have been PG once ended with an ectopic pregnancy...HURT BEYOND BELIEVE. Headed to doctor in an hour for blood test, don't want a negative result. Can't talk to anyone I know because I am tired of being disappointed. Praying for +++

      • profile image

        kia 3 years ago

        Hi everyone I had my mirena removed last Friday and me and my boyfriend had been very sexually active for the pad couple of days I have been having lower cramps as well as being very sleepy. I took a pregnancy test it came back negative I an thinking that I might be to early to tell. Any suggestions on why I am have these cramps? Are when to take another test?

      • profile image

        lisa 3 years ago

        I just found out i am pregnant. Took 2 hone test and got blood work done. All are positive. But i am having a dull pain on my, right lower back side. And under my right rib.

        Does antine know if this is normal?

      • profile image

        steph 3 years ago

        Yes, but it could also be your body adjusting

      • profile image

        Jordan Yates 3 years ago

        I've taken pregnancy test several times, I have hard and sore nipples , and white in the tips of them, I have a white discharge that I've seen on the internet it's a yeast infection but my friends who have been pregnant say that they only had a white discharge during pregnancy and that a yeast infection is discolored. I have taken 3 test all look to be negative the the most resent I have taken shows negative but if I tilt it or hold a light under the test there is a clear line, but the other two test doesn't have the clear line under the light. I've had cramps and bloating feeling , and some nausea . I resentful had my nexplanon birth control removed from my arm, the doctor said I should have a period in a couple days after it was removed but it's been a month and I've had no period yet! Could I be pregnant?

      • NathaNater profile image

        NathaNater 3 years ago

        Nicole, it might be a good idea to see a doctor and see if you can have a blood test done; they are more accurate and reliable.

      • profile image

        Nicole Franco 3 years ago

        I'm 19 days late on my period i have taken 3 home tests and they are all negative i pee frequently and my breast are really tender to the point to where i can't even lay on them i am a little worried

      • NathaNater profile image

        NathaNater 3 years ago

        Good luck, Shai. Sounds hopeful. Hopefully your daughter will soon have a brother or sister.

      • profile image

        Shai 3 years ago

        I've taken 9 first response pregnancy tests all showed a very faint positive I'm Supose to start my period in 3 days I have a drs appt in 2 days so I'm gonna have another test done when I go hopefully I am I have a 3 year old daughter and she needs a brother or sister :) wish me luck

      • NathaNater profile image

        NathaNater 3 years ago

        It is safe to take the PPD test if you're pregnant and pregnancy will not affect its results. But it is wise to consult a doctor and tell medical professionals that you think you might be pregnant. Also, one of the routine tests during pregnancy is a blood test for rubella. However, you cannot be immunized if it turns out you're pregnant because it could hurt the baby. So, if you are talking about immunizations, you should not have them done if you think you are pregnant.

        If you had implantation bleeding before and during your missed period, that could be a sign that you are pregnant. The urine tests could be inaccurate, especially if you've had something to drink because then the urine is diluted; it is best to take them in the morning before you've had anything to drink. The blood test is much more accurate, 99% accurate, because it can detect the smallest traces of the pregnancy hormone.

      • profile image

        beth 3 years ago

        Well I am confused because I am late from my period a week and 2 days and I've taken two hpts and they were negative and went to planned parent hood had pee test it was negative but I truly believe I am pregnant but to early to show I had what I think was implantation bleeding 3 days before my missed period and some throughout when I was sup post to get my period and its been a week since that should I get a blood test. And I am getting a new job and need rubella and rubeolous and PPD done I don't know if that will affect if I am pregnant


      This website uses cookies

      As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

      For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: ""

      Show Details
      HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
      LoginThis is necessary to sign in to the HubPages Service.
      Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
      AkismetThis is used to detect comment spam. (Privacy Policy)
      HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
      HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
      Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
      CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
      Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
      Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
      Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
      Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
      Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
      Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
      VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
      PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
      Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
      MavenThis supports the Maven widget and search functionality. (Privacy Policy)
      Google AdSenseThis is an ad network. (Privacy Policy)
      Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
      Index ExchangeThis is an ad network. (Privacy Policy)
      SovrnThis is an ad network. (Privacy Policy)
      Facebook AdsThis is an ad network. (Privacy Policy)
      Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
      AppNexusThis is an ad network. (Privacy Policy)
      OpenxThis is an ad network. (Privacy Policy)
      Rubicon ProjectThis is an ad network. (Privacy Policy)
      TripleLiftThis is an ad network. (Privacy Policy)
      Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
      Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
      Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
      Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
      ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
      Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)