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Question

11 Jan 2005

Urine HCG test vs. Blood HCG test
A friend of mine did a home urine hcg test 3 weeks after missing a menstruation and it showed negative. then when she missed a second one she did another test which also showed negative so she went to her GP who suggested she go for a blood test. it was positive and she was about 10 weeks already - how can this be?
Answer 689 views
Expert
pathologist

01 Jan 0001

The urine HCG tests are not as reliable as the blood test. The blood test is much more sensitive, and will detect pregnancy much sooner than the urine test. The estimation of duration of pregnancy is only a guideline, as the values of HCG may vary substantially between pregnancies. However, the estimate of 10 weeks would fit in with the blood test being done after 2 missed menstruations.
The time period is calculated from the last normal menstruation, which would have been approximately 10 weeks before the blood was taken.
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