Blood Drug Testing

are blood pregnancy tests ever wrong?

My little sisters last period ended December 5th. She has taken four first response pregnancy tests three which came back positive. She went to the doctor and they had done a blood test to check if she was pregnant, that came back negative. I was wondering if it is possible that she is pregnant and they were wrong? She could be no more than a month pregnant if that, probably less. She is also experiencing some signs of pregnancy. Another friend of mine didn't show up positive on a blood pregnancy test till she was two months pregnant. I was also thinking it depends on the person, because every pregnancy is different.

Public Comments

1. She needs to talk to the doctor about this, she also should have told the doctor about the positive tests.....it's very possible she had a miscarriage. The blood test is much more accurate than the urine test. Tell her to go back to the doctor.
2. it could be wrong, nothing in this world is 100%, i would go back to a different doctor and get another blood test, and if u have the money i would get another preg. test and follow it just like the directions says
3. Not usually
4. The blood test itself would have less than a 0.001% failure rate b/c it's not just "yes" or "no"-- it measures how much pregnancy hormone is in your blood. However, it could have been mixed up with someone else's test, measured incorrectly, or your sister may have had a chemical pregnancy (very early "miscarriage"-- the egg just never implants into the uterus).
5. my blood test was wrong!!! so yes very possible