Nathan has two daughters. When he and his wife were trying to have a baby, they did considerable research on issues concerning pregnancy.
Dr. Mark Trolice, Director of Fertility Care, The IVF Center
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?
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.
Pregnancy Blood vs. Urine 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.
- 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:
- Biochemical pregnancy, or a pregnancy that is lost before the woman even knew she was pregnant.
- 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.
- 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.
This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
© 2014 NathaNater
Ruth on June 11, 2020:
Hi..ive been having cramps and pain in my lower bk 2weeks before my period date and now im 1week 2days late for my period,but im still getting period like cramps.i took 2 urine test and 1 blood test,both came bk negative..im confused..need help
aisha on January 06, 2020:
I had sex a day before my ovulation mean to say I was on my fertile day and my ovulation was the next day and I had sex a day before that....is it possible to get pregnant
Kaylee on December 15, 2019:
Ill adopt your kid paula lol
Sharon on September 09, 2019:
I had unprotected twice I. the month of September 2and 3.2 of September was my ovulation time and my period is schedule to come on the 17. But I want to know if I can do a pregnancy test before my period time to know if I'm pregnant or not
Clara on July 12, 2019:
You say that a urine test is only accurate done a week after a missed period. This is inaccurate.
Lovely on October 24, 2018:
Hello, i would like to ask for your help, i have a 34 day cycle, and had unprotected sex last 27th of september, i have been cramping for 2 weeks then I've missed my period that was supposed to be on the 17th of October, now im 6 days late, i took a urine test last saturday on the 20th with negative result and on the 22nd I took a bloodtest with another negative result, so I assumed i was not pregnant , but the day after that i had some spotting and it stopped the next day and i still feel some cramping, please help is this because of stress or am i really pregnant?
Kim on September 18, 2018:
Hi..ive been having cramps and pain in my lower bk 2weeks before my period date and now im 1week 2days late for my period,but im still getting period like cramps.i took 2 test and both came bk negative..im confused..need help
May on September 07, 2018:
Hi there I have a line under my belly button to the pelvic and most pregnancy symptoms but my main worry is the line but got negative test and just took a blood test so I have to wait need help thank you
amanda on August 14, 2018:
How do I know I am going to be a mother for the first time.
lydia on August 11, 2018:
i have i week after unprotected sex and am experiencing some change in mybody but i got my period earliar than usual and its regular could i be pregnant
Paula on June 28, 2018:
When i take blood pregnancy test ( which is part of the requirements of my work) the result came positive I was shock because I didnt have sex to my boyfriend and when I take the home pregnancy test it came negative result, now I missed 9 days of my period and my breast is hurting I dont know if this is stress because I’m not yet ready to have a Child and I’m confusing because there’s nothing happen to us (boyfriend) What do you think?
Alexis on June 19, 2018:
I have Nexplanon which is a birth control that is highly affective due to not getting my period ever I have no way of knowing whether I am pregnant. I have been having some sharp cramping in my lower uterus area and I've been extremely tired all the time. I recently (a week ago) took a at home urine test and it was negative. Should I just go to the doctors and have a test done? Does anyone know of pregnancy symptoms you might have while being on this type of contraceptive?
Rae on April 13, 2018:
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!
Stella on March 25, 2018:
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.
haseena on March 25, 2018:
1st i missed period so i take pregnency test how many days to take
larissa on March 13, 2018:
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
Marissa Henderson on March 05, 2018:
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
Emily on March 05, 2018:
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?
rossy on February 06, 2018:
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????
Ann on January 26, 2018:
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?
Katie on January 06, 2018:
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.
JENN on December 27, 2017:
I HAD SEX ON DEC 3RD, THE IUD WAS TAKEN OUT DEC 4TH AND GOT MY PERIOD ON DEC 6TH. CAN I STILL GET PREGANT FROM THE INTERCOURSE THAT TOOK PLACE ON DEC 3RD?
Samvia munir on December 16, 2017:
My serum test positive what I do
glory on November 17, 2017:
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???
Star on November 05, 2017:
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
i am Helen i got pregnant for 5 days carried out blood test but still negative on October 27, 2017:
I am Helen I got pregnant for 5 days I carried out blood test but still negative
Lori ward on October 11, 2017:
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
Xxxx on September 07, 2017:
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?
Mary on September 04, 2017:
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.
Special Kay on September 02, 2017:
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?
Kayla on September 02, 2017:
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?
Xmen on June 25, 2017:
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??
DONT KNOW ANYMORE on May 29, 2017:
I WAS DIAGNOSED WITH PCOS, WENT ON CLOMID FOR 3 MONTHS, THIS WAS MY LAST CYCLE, DID NOT GET THE USUAL SYMPTOMS OF PMS, SO STARTED TO WONDER, TOOK A HPT 6 DAYS BEFORE MY PERIOD IS DUE, THE TEST GAVE A FEINT POSITIVE WITH FIRST MORNING URINE, TOOK ANOTHER ONE A FEW HOURS LATER, THAT WAS NEGATIVE, I WENT FOR A BLOOD TEST THE SAME DAY IN THE AFTERNOON, ALSO NEGATIVE, SO COULD I STILL BE PREGNANT? PERIOD IS EXPECTED WEDNESDAY...
Peanut on May 21, 2017:
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
Larissa on April 27, 2017:
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
Annabel on February 07, 2017:
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?
lexie on September 08, 2016:
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
Pequena on May 04, 2016:
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
Neha on January 05, 2016:
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?
elizabeth on October 26, 2015:
am 10 days to my menses,can blood test detect if am pregnant?please any help
Jenn on October 08, 2015:
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
Carlota on October 03, 2015:
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 ??
Ivone on July 31, 2015:
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 :)
Chrissy on June 01, 2015:
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.
vicky on May 28, 2015:
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.....
laurice on May 19, 2015:
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 +++
kia on May 12, 2015:
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?
lisa on May 06, 2015:
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?
steph on April 01, 2015:
Yes, but it could also be your body adjusting
Jordan Yates on March 30, 2015:
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 (author) on February 20, 2015:
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.
Nicole Franco on February 19, 2015:
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 (author) on January 14, 2015:
Good luck, Shai. Sounds hopeful. Hopefully your daughter will soon have a brother or sister.
Shai on January 14, 2015:
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 (author) on January 06, 2015:
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.
beth on January 06, 2015:
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