Can Blood Tests For Pregnancy Be Wrong?

As a general rule, blood tests for pregnancy are more reliable than urine or home pregnancy tests. But they can be wrong. That means, they can show false negative or false positive results in some women. To understand why this can happen, let us understand what blood pregnancy tests are, how they work and what do their results mean.

Blood Pregnancy Tests

A pregnancy blood test or a pregnancy serum test is a test that measures the exact amount of the pregnancy hormone, human chorionic gonadotropin (hCG), in the bloodstream.

Human chorionic gonadotropin (hCG) is a hormone that is produced by the placenta of a pregnant woman. It is detectable in the blood and urine within 10 days of fertilization. There are two types of blood pregnancy tests, namely, quantitative blood test which measures the exact amount of hCG in the blood and qualitative hCG blood test which gives a simple yes or no answer to whether you are pregnant or not.

Blood tests can detect a pregnancy earlier than a home pregnancy test (about 7-12 days from possible conception) and can also measure the concentration of hCG hormone in your blood (this is useful information for your healthcare provider in tracking certain problems in pregnancy). If you suspect any symptoms of pregnancy like delayed menstrual period, breast tenderness, pelvic pain, irregular spotting or vomiting. You must get a pregnancy blood test done to confirm or rule out pregnancy.

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What do the pregnancy blood test results mean?

A healthy pregnancy is expected to show a normal pattern of HCG levels over time. In a pregnant woman the level of human chorionic gonadotropin (hCG) increases throughout the first trimester, then gradually decreases over time. In the first trimester, a woman may have this test done repeatedly to see if the level rises normally. If it doesn’t, the pregnancy is often considered in trouble. After childbirth, miscarriage, or abortion, the level should quickly decrease to zero.

Wrong results with blood pregnancy tests

The test may fail to detect human chorionic gonadotropin (hCG) even when a woman is pregnant if the test is done too early. It takes at least 7 days after fertilization for the test to become positive. In most cases, by the time a woman has missed her period, the test will be positive if she is pregnant.

Greater than normal levels of human chorionic gonadotropin (hCG) may indicate:

  • a tumor of the placenta with death of the fetus
  • multiple pregnancy, such as twins or triplets
  • ovarian cancer and other types of cancer in some cases
  • a normal pregnancy
  • blood or protein in the urine, which can interfere with the result
  • use of medications to prevent seizures, drugs to treat Parkinson’s syndrome, or phenothiazine drugs, such as chlorpromazine, by the mother

Lower-than-normal human chorionic gonadotropin (hCG) levels may indicate:

  • ectopic pregnancy
  • a miscarriage, or abortion.

How reliable are blood pregnancy tests?

Home pregnancy tests are around 97% accurate when done correctly. However, a blood test is more accurate, but not necessarily more sensitive. The results depend a lot on the lab, methodology and technique of the blood test performed.

A quantitative blood test, usually called a beta human chorionic gonadotropin (hCG) test, measures the exact units of human chorionic gonadotropin (hCG) in the blood. That means it will detect even the most minimal level. There is another type of blood test sometimes called a qualitative human chorionic gonadotropin (hCG) test. This is a test that simply gives a yes or no answer to whether you are pregnant.

Just like home pregnancy tests, labs vary in what is considered a positive pregnancy test. Common cutoffs for positive blood tests for pregnancy are 5, 10, and 25 units. A level under 5 is considered negative. A blood test that is only triggered at 25 units of human chorionic gonadotropin (hCG) is not any more sensitive than several of the home pregnancy tests.

  • Vickie B.

    If you have a normal 28 day cycle, the ovulation calendar shows you would have ovulated on July 5th. The timing of intercourse would have been too late to result in a pregnancy.

  • Samantha

    So I was supposed to get my period on July 11th, it showed up 4days later on the 15th and was extremely light, barely anything on the tampons but it has become slightly heavier and today it is gone It is definitely not my normal period. Normally the first day I’m stuck in bed in a lot of pain or in the bathroom throwing up. I can fully function now and have little cramps. I had my doctor do a blood test but it came back negative. Was it to early to test or am I just not pregnant?

  • Sravani

    I was unmarried.i met with my boy friend on 15th june with condom and i took an i.pill too.still now i didnt get my period.i did my home pregnancy tests 6 times up to date i got only negative 6times and i went to a gyenococlogist she gave me a meprate tablet to get my period i completed my dosage i still didnt get my period and then she wrote blood pregnency test and it results negative…stil i didnt get my period…what to do now?

  • miss123

    my husband and I have been ttc and this month I was only 1 day late but the first day started with light brown spotting then I only had my period for 2 days(light) it always lasts 6-7 days. I took preg. tests-negative. Blood Work negative. If I calculated correctly we would have conceived between 7/4-7/6. Did I test to early for preg. tests and blood work?

  • miss123

    my husband and I have been ttc and this month I was only 1 day late but the first day started with light brown spotting then I only had my period for 2 days(light) it always lasts 6-7 days. I took preg. tests-negative. Blood Work negative. If I calculated correctly we would have conceived between 7/4-7/6. Did I test to early for preg. tests and blood work?

  • Volleyball_Chick

    I am pretty sure my last period was July 8th (or earlier) through July 13th. I have not yet had it – and I have not experienced any “spotting.” I had sex for the first time ever with my fiance of five years on July 27th – July 28th (depends on the time – like it was around 11PM… so not sure if that matters). I have not yet had my period in August and I am concerned that I am pregnant. My period is usually normal – like 28 days cycle. I hardly ever get it pushed back. However, when I was in college – I would get stressed from time-to-time and it would push back my period.

    QUESTION: Could I have got pregnant if I had sex that night? Not sure when I would have ovulated. I am not interested in having a baby now because I am currently planning my wedding. When are the most likely chances of you getting pregnant? Like, do you count the first day of your period or last day of your period? I don’t know! Also, could I just be super stressed because it was the first time I ever had sex?

    This is the longest I have skipped my period. It has almost been 40 days and I am freaking out. I did 3 HPT and they all came back negative. I did 2 on missed period day 5 (night) and one the following morning since I heard that is the time you are supposed to do it. Okay, well I did it around 3AM – so I hope that time is okay! After I did those tests, I still did not believe it because they could be defective. So I went to the doctors. On missed period day 7, I did a blood test – the next morning they called and informed me the test was negative. So okay, that is fine, but where is my period!!!

    QUESTION: Should I take a HPT on Sunday morning? I just want to know… :(

    Last week- I started to feel weird. Last Sunday (August 11th) I woke up with this killer charley horse. Now, I do get them from time-to-time, so its not like unusual. This whole week has been strange. I hardly got ANY sleep because I was not tired at all. I hardly had anything to eat because I was not hungry at all. I felt like I was going to throw up most of the time so it was very random. Sunday and Monday night I had killer night sweats. I couldn’t sleep at all – I was soaking wearing NO clothes. However, I have not had that problem at all since Monday night. For this whole week – I had trouble going number 2 for the bathroom if you know what I mean. Just last night, I finally went number 2 and it was kinda like diarrhea.

    Recently, I have changed my workout schedule. In July, I started this new routine. This month, I picked up and started to improve my schedule from July because I missed a few days. Since August, I have been to the gym 9 out of 17 days. Usually, I lift weights so I am not sure if that could have messed up my period schedule? I also started to drink protein shakes back in July – so not sure if that could have done something to my body… idk! Or could I have too much protein in my blood that could have caused incorrect blood tests?

    I think I have been feeling better – but it could all be in my mind.


  • Vickie B.

    Our ovulation calendar shows the following for July, based on the information you provided:

    Monday 8th July 2013 – First day of your cycle
    Thursday 18th July 2013 – A little bit fertile
    Friday 19th July 2013 – Fertile
    Saturday 20th July 2013 – VERY fertile
    Sunday 21st July 2013 – Time to ovulate

    Based on your timing, you would have had sex after you ovulated making getting pregnant not possible.

    You have taken the tests, had a blood test and they all came back negative. I would trust the results and assume you are not pregnant.

    You have a couple of things that could cause your cycle to go wacky.

    - Changing your exercise intensity
    - Changing diet
    - Change in stress level.

    If you are really concerned, you may want to ask your doctor about it, but if you give your body a chance to get used to the changes you have made, you may notice regularity returning.

  • Cortneytucker57

    I am 14 days late, went to the dr. When I was 12 days late and they did a pee test which came back positive I got a call on the 14th day of my missed period saying that my blood test levels were too low saying I was not pregnant. Is there still a chance that I am pregnant?

  • Vickie B.

    Until you get a period, there is still a chance. If you don’t get your period in a week or so, I would suggest that you get the doctor to do another blood test to see if the levels are raising at all.

  • confused

    My last period was on june 21. I did have light spotting when I whiped only near the time I should have had my period. I have taken hpt they all say negative yet stilll no period I have all the symtoms exept morning sickness. I just turned 47 could I be pregnant or is it menopause?

  • BGrundlingh

    My last period was started on the 16th Of July, I am now 3 weeks late, my breast are very tender, especially around my nipples but all the home tests have come back negative. Can I be pregnant?

  • Christa Marie

    Hi im feeling pregnacy systoms but i took two prego test both came negative can i be pregnant

  • Kaylie

    I am currently 3 weeks late on my period. My last period started on July 17. I have had unprotected sex and I have done 4 pregnancy tests up to this date. I had one done at the hospital at 10 days late it was a piss test and it came back negative a week later I took 1 more home pregnancy piss test and it showed negative a couple days later I did the same and still negative. On the third of September I went to the doctors and took a blood test that came back negative. Is it possible that I could be pregnant and it was just to early to tell?

  • becky

    Hi I’m a mom to 3 and after my third child i had my tubes tied 5 1/2 yrs ago and always been on time since then until now my last period was July 28 I’ve been having the same symptoms I did with my 3pregnancies but had a bata hcg blood test done came back neg should i be worried or just wait

  • laura

    I am almost certain i had a miscarriage on Saturday but when i had my bloods checked at the hospital it came back negative? But there was a fetus that i seen but i dint take it to the doctor i was to scared so i cnt prove what it was, is there anything else it could be? I had all the symptoms of miscarriage and missed 2peiods so in almost certain? Thanks

  • Kara


    Okay so here is my situation. A little over a year ago I miscarried. September came around and I was four days late but I had been getting a lot of comments before I had started that I looked like I was getting a “pouch”. (Like I was pregnant). My boyfriend was concerned because he said I had been acting just like I did when I was pregnant a year ago and ended up miscarrying. So on the 3rd day that I was late I went and had a blood test done to see if I was pregnant. It came back negative. About a week and half later I ended up getting a bad sinus infection. Well during this infection I started to obtain sharp abdominal pains off and on. I went to the doctor who put me on sudafed. It has been a week since I got sick and now I have random symptoms that I am unsure of what they pertain to. (either the infection or me being pregnant) For a week now I get sick every morning when I wake up. I still have a bad cough but I also have symptoms of nausea and dizziness throughout the day. Especially when I get up and be really active, I will get hot flashes and then get nauseous and dizzy. Do you think I could be pregnant?

  • Amber

    I’m 11days late, which is so not usual. I’ve never been this late before. I took a urine test 4days ago and it was negative. I don’t have any other normal pregnancy symptoms but I can’t understand why all of a sudden. Plus I haven’t had intercourse in 3months. I was in the emergency room for severe dizziness about 2months ago. They said they ran a blood test to confirm i was not pregnant before doing a ct scan and said it was negative. Would a urine and blood test give a false negative in that amount of time from conception?

  • Vickie B.

    Most likely not, but if you are worried, you should go to your doctor and ask for a ultrasound. If you are pregnant, the baby would most definitely show up on an ultrasound now.

  • ADE

    I had last menstrual period on the price25th, of Sept,my husband told me to get a pregnancy test because am having all the signs and symptoms. The blood tests are all positive, started sporting today ( 19th).the scan did not show anything. Am i pregnant

  • Vickie B.

    What do your doctors say? If the blood test showed a positive result, you are pregnant. Spotting during early pregnancy is not uncommon but if you are worried, you will want to talk with your doctor about it.

  • Angel

    Hi Vicki,

    I took four pergnancy test and I saw faint lines on sone of them for a positive result. I went to the doctors and i came up negative on two pee test and one blood test. But I can’t believe it I’ve been getting really randon migraines, im starting to feel nausea and I’m getting back pain like i never have before. It hurts near my tailbone my butt and to my thighs. Would you suggest me to wait out a couple weeks. Because if I am pregnant i think i should be about 3 weeks now. I don’t know i have this gut feeling i am because i know my body very well and I’ve never had back pain or headaches like this before.

  • Britanny Bowers

    I haven’t had a period since August. 2013 blood test show neg for pregnancy. Which doesn’t surprise me. If I were I would have to be around 8 weeks and I seriously doubt the test could be wrong. What else can stop a period from coming for two months?

  • Vickie B.

    Have you seen a doctor about this? Stress, PCOS, other medical issues, weight loss / gain, increase in exercise can all cause a change in your cycle.

  • Vickie B.

    Has your period arrived yet? If not, has you gotten any positive results on your pregnancy tests?

  • Jen

    I’m late, taken four hpt’s and just had a blood test—all negative. I’ve had headaches, nausea, lower back pain, white discharge, lower pelvis cramping, slight breast tenderness. I’ve been pregnant three times before (1 miscarriage, two healthy children) so I know the symptoms. My last period was October 13-18, 2013. I’m so confused and stressed about this. I feel like I’m going crazy! Anyone going through a similar situation? Please help!

  • marian cruz

    same thing here, im nauseaus, my lower back hurts, my last period was sept 26 all negative results but no period. i need help figuring this out

  • Tara

    I was three days late, positive pregnancy test at first…back pain, headaches, nausea, fatigue and pelvic pain…symptoms I never have before my period…tenderness I breasts was the only typical thing. Few days later started spottin an then bleeding. Took another hpt and it was negative and a blood test..also negative. Weirdest thing. I still can’t explain it

  • Vickie B.

    Unfortunately, it sounds like you had a miscarriage.

  • worried

    I have the essure birth control. I am 1 week late if not longer. I have heard of women getting. Pregnant on this. I had light bleeding one day almost like diluted red water. For like 5 minutes. I have had nausea and all the symptoms cramping but no period. I tested on the 16 and it was negative. Did I test too early? My last period was in December last day was about the 14th could I be pregnant?

  • mzzbarker

    I had my last period Jan 24th, Feb 7th I took a hot and it was faintly positive…I bought 3 more of different brands and they were all positive. I went to the doctor a and he did a blood test which was also positive. Yesterday (2/22) I began to spot. Today (2/23) I bleed every time I void (pee) as if i’m having a period. I bought a hpt today (2/23) and the result was negative…am i pregnant or not? Should I call my doctor?

  • Brooklynn

    I am going through the same exact thing. My pregnancy test said positive today at the obgyn. I am 4 days late and waiting for my blood work results Monday. I started spotting when I left. This bass happened to me before. The doctor gave me a pee test about 5 years ago, it said positive and blood work came back with hormones at zero saying I’m not pregnant. I hope it isn’t happening again. I am now worried until Monday. Why would a teT say positive and blood work say negative? Weird is right!

  • Kristie Meleen

    2 positive confirm hpt then negative <2 blood test, last p beginning February had sex 17th n 18th unprotected?
    HELP last week I done 2 hpt one faint both visible positive bloods done 3 days later <2 negative, period late by 9 days all symptoms no bleeding at all n slight yellow discharge is the hpt wrong or the blood I'm trying to get another blood done but Dr thinks I'm a nutcase used a friends paperwork for another test today just waiting for results, what would make a test a false positive, has anyone experienced this before l had ectopic 4 yes ago

  • Sandy

    Endometreosis can make ur period 2months late along with pcos have ur dr to check u for that I have gone threw this at 22 and I’m 27 now and it
    seems like I’m going threw it again and this can give you the same symptoms of being pregnant

  • Suzanne

    BLOOD PREGNANCY TESTS CAN BE WRONG!! It is VERY possible to be pregnant with negative urine and blood tests! This is what is known as a “Cryptic Pregnancy”. I have created a support group for this on Facebook called “Cryptic Pregnancy Support Group”


    I have a baby bump and just spotted, however, all my tests were neg from blood and urine. What could be happening. The doc dont want to do anymore testing to rule out other things. What do I do?

  • H

    I am a few days late. I have all the symptoms and I got 2 positive pregnancy tests the other day but when I went to my doctor’s office yesterday they ran a pregnancy serum blood test and it was negative. When I had my daughter they did both quantitaive and qualitative because they wanted to know the numbers of my hcg level. they did not do this this time. could I still be pregnant?

  • kerry

    I was due on my period 20/4/14 I was being sick at the same time every day, really tierd and emotional, never came on so I went to the doctor. they did a blood test for pregnancy on the 13th may and it came back negative. I still felt like I had morning sickness, bit faint at times and tierd so 23/5/14 I did a hpt and it was positive. could the doctors blood test be wrong?

  • OLA

    I av been TTC for 9yrs with so much done. Recently I av started feeling all d symptoms of pregnancy and I opted for blood test which came out negative. My last period was 21st April 2014 and yet to see it. My average cycle is 26 cos it’s sometimes 27 or 28. Pls what do I do next. I am so confused.

  • Crystal

    hi name is crystal on May 17th 2014 I was supposed to start my cycle last time I had a cycle was in April but in May I started antibiotics so I may 17th my Cycle never started I didn’t notice until that Sunday when I started my new birth control I had taking home test they came back negative and a blood one that said negative there in a middle of doing another blood test cause they think the other one was to soon I know the symptoms I’m having I’ve had to Cycle for 10 years now I have never had a problem On or Off birth control I know my body and something ain’t right I have a daughter the symptoms I’m having are the same I need some help

  • kkiernan

    My lamp was April 3 2014 I had my Korean removed may 16.. on May 31 I got 2 positive results with home pregnancy tests. I ended up in the er on May 10 because of a sharp pain I was having in my ovary. Long story short doc tells me my blood work was negative for pregnancy. I have taken 2 more hpt with negative results. I have when my last actual period was or when I could have been ovulating. I’m basically going by when my iud was removed. I have 4 children and was hoping for a 5 th. Any feedback……oh and still no period.

  • Kat

    My periods are irregular, I never know when they are gonna happen, how long they will be, or how heavy they will be. I was having unprotected sex and when my period was 4 days late( which isn’t unusual) I took a pregnancy test and it came back negative. I took another pregnancy test when I was a week late because I didn’t have any normal menstrual symptoms but I had tender breasts which isn’t normal for me, it too came back negative. I also started what I thought was my period that same day I took the second pregnancy test. My period was extremely heavy and lasted for 7 days. After it ended I started having unprotected sex again and 7 days after my period ended(today) I took a pregnancy test, it came back positive. I took a second one and it was also positive. I went to the hospital and had a blood test done and it came back negative.. When I got home I took a 3rd pregnancy test and it came back positive. Could I still be pregnant? Is it possible that I had a miscarriage? I plan on taking more home pregnancy tests in about a week.. I used first response home pregnancy tests.

  • Vickie B.

    If you keep taking pregnancy tests and they come back positive, you have the pregnancy hormone in your urine. It could be that the level of hcg is lower than what the blood test picks up. First Response is one of the most sensitive pregnancy tests. If you wait a couple of days and have a blood test, again it should pick up the pregnancy. It could also be an early miscarriage, in which case you will eventually end up with a negative pregnancy test.

  • sharon

    I had my tubes tied in 1999 I had to go thru 2 different laproscopic surgerys in the last 4 months and have been doing nothing but throwing everything up since these surgerys so they did a pregnancy test it came back positive I told them they were crazy so they did the dip stick it came back neg symptoms continue so my general dr did some labs on me my hcg came back showing pregnant so she ordered more labs with blood and urine blood came back at 5 which usally means your pregnant so they told me I need to go see obgyn I am so stressed over this right now going for ultrasound on Wednesday hope it will tell the truth.

  • lucy

    Hi I thought I was about 7 weeks pregnant since I still haven’t gotten my period since may 20th I had some spotting the other day and went to the doctors and my blood test came back negitive but I have had 10 home pregnantcy come back positive. Could the blood test be wrong?

  • Carrie

    Hi my name is carigan and im in that same boat I have every symptom of pregnancy but everything is negative and I even feel flutters in my stomach from time to time so im not understanding!!! Help??!!

  • Emily Rose Shelley

    That happened to me too, did you ever find out what the situation was?

  • Nekea Dishon

    my last period was june 2nd i took a home test the 8th of july and it was positive went to the doctors and had a blood test the 11th it came back negative went home and took a clearblue pregnancy test which came back positive i still havent started and im so confused

  • Vickie B.

    What does your doctor say about that? It would appear that you are suffering from a miscarriage or the blood test is incorrect. If you wait 3 or 4 days and you don’t start your period and a hpt comes back positive yet again, you should definitely contact your doctor again and ask them what is going on.

  • gracejames??

    Have you found out whats happening yet?? I was due for my period on the 24th june and it never came, i had 4 early home preg test come back negative and one blood test come back neg (all in july) then 21 days after missing my cycle i got a positive blood and positive home test.. but now im paranoid there is another reason they were positive and its not due to pregnancy… i am by calculators 7weeks and 5 days…

  • chaparita 17

    Hello, June 15 I started workout, June 18 I started to bleed a little bit it didn’t look like if it was my menstruation, so I decided to go for a blood test and the test said it was negative. July and no period yet, July 21 I went for a next blood test and showed negative again, can some tell me if I can still be pregnant if two blood test came out negative?? Plz help

Last modified: February 10, 2013