Can a Blood Test Be Wrong?

Updated on November 05, 2007
A.C. asks from Lincoln, CA
12 answers

Ok, I am asking this question for my cousin. Her period is almost 3 weeks late, and all of the home pregnancy tests have been negative. She is usually very regular on her periods, so her doctor recommended a blood test at the lab. She got the results back yesterday and it was also negative. She hasn't actually seen the doctor yet, but she will soon. What could be causing this? She usually always has a 28 day cycle. Could the blood test be wrong? I've heard that they are pretty accurate, but maybe it's not 100%. If she was pregnant, she would be almost 7 weeks by now, so what is going on? Any input would be helpful, and I will pass the info along to her. I know she would appreciate it! She's very confused, and she really wants to be pregnant!
Thank you.

*Someone asked how old my cousin is - she is 24. Also, I would say that she has a lot of stress only because she wants so badly to be pregnant! They have been married for a little over a year, and they really wanted to be pregnant by now.

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L.L.

answers from Los Angeles on

I heard that blood tests are the most accurate. But if your cousin feels that it is wrong then she should wait until she sees the dr. She's knows her body better than anyone else. I'm actually going through something like that. I've taken tests after tests and they are negative so tomorrow I'm going for blood work. Well I hope everything turns out to her advantage.

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F.F.

answers from Los Angeles on

Maybe she is tricking her mind and body into thinking she is pregnant, because she wants it so bad. Sometimes we can do things like this to our selves and not even know it. It could be something else all together that that requires medical attention. It could be a good thing this happened if medical attention is needed. Either way i will pray for the best. By the way i took several test that said i was not pregnant and i was showing. The dr.said they would not see me untill they got a postive urine test(i had a hmo. By that time i was 6 mos. I had to go outside of the hmo to get a blood test that tested postived. Good luck

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S.D.

answers from Los Angeles on

How old is your cousin? The blood tests are usually pretty accurate, so long as you're at least 10 or more days pregnant. If her period still hasn't come, there is a chance she ovulated late, that she is not as far along as she thinks. In addition to the other reasons listed as to why periods don't come, some other reasons are weight gain, weight loss, the lining not building up to shed, too much exercise or dieting, hormone levels being off and age. You can also have regular periods when you're pregnant. The only way to be certain is a physical exam and a positive pregnancy test.

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J.I.

answers from Los Angeles on

A missed period can be caused by a number of things. Poor nutrition, stress, people who are very athletic with a rigorous workout routine are also prone to missed periods. Also your cousin may have developed anemia (low blood-iron count) which changed my cycle dramatically. Until she sees her doctor, she won't really know the cause.

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J.L.

answers from Sacramento on

It is unlikely that they are wrong. Stress can affect menstral cycles as well as some other things. I am sure her doctor will do a complete check of everything. It is possible to have false negatives however but at 7 weeks it is highly unlikely. Her hormone levels would be high enough to be detected.

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J.S.

answers from Stockton on

Chances are she's not pregnant. A lot of things can cause you to miss a period. Even stress.

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R.W.

answers from San Francisco on

Hi A.,

There are soooo many things that can cause a break in the menstrual cycle. It can be stress, illness, too much exercise and a host of other medical reasons. If her period doesn't start I would suggest that she see her GYN as soon as possible to rule out any medical disorder. It would be pretty hard to say if a test was negative without an exam. It is usually the first indicator of a pregnancy based on the hormone levels that are present during pregnancy. I would think that it would have detected a pregnancy if there was one. Overall, the best option for her is to seek good medical care and remember that you can occasionally miss a period and its perfectly normal. Good luck and take care!

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E.T.

answers from Los Angeles on

YES! It can be wrong! I have experienced this. I was very, very sick and my period was late. I had been told I was infertile due to PCOS and so was not expecting that I could be pregnant but took multiple home tests to be sure. I saw the doctor several times as well. I had negative tests with them both blood and urine. During this time I was so sick I lost 27 lbs and began to think I was dying of some horrible disease. They had actually put me on a hormone to start my period as well because they were so sure I was not pregnant. Finally the doctor did a physical exam and said that he did not believe I was pregnant but sent me for one last blood test. That blood test came back positive and I was 8 weeks pregnant.
So basically I would say she could absolutely still be pregnant...good luck!

Smallavatar-fefd015f3e6a23a79637b7ec8e9ddaa6

S.T.

answers from San Diego on

That happened to me once, I was nuts because my period was always right on cycle. I stopped having periods for a few months and then they came back, my Dr. said it was not uncommon for that to happen.

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K.F.

answers from Los Angeles on

Yes, the blood tests can be wrong and so can the urine tests. This actually happened to my cousin. In some women it takes a lot longer for the pregnancy hormone to be strong enough to detect. They finally confirmed that she in fact WAS PREGNANT through an ultrasound. They could see the sac and the baby.

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H.F.

answers from Los Angeles on

This has happened to me a few times for various reasons. I usually have very regular cycles but at least twice I have had a period late by 3-4 weeks. Both times I thought I was pregnant as well but several home tests and a few blood tests all were negative. I was not pregnant either time.

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K.H.

answers from San Francisco on

Her period could be this late for a number of health reasons other than being pregnant. I highly doubt that all of those negative test result are wrong. Has she changed her diet or started a more intense excercise routine? She should see her gyno who will probably offer her a number of possible reasons. I'm sure it's nothing to worry about.

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