Why Was My Home Pregnancy Test Positive, But My Blood Test Negative?
Typically, after you get your positive pregnancy test, or tests if you are a testaholic, the next step is usually a visit to your doctor for confirmation. If your pregnancy blood test has a negative result, you need to have another blood sample drawn. Home pregnancy tests are very accurate, when you follow the directions exactly. Blood tests tend to be more accurate, but are not necessarily more sensitive. The blood test results received can vary depending on the lab, methodology and technique used to perform the test.
Quantative blood tests measure the exact amount of hCG (human chorionic gonadotropin) in your blood and can pick up very low level of hCG present.
Quantitave blood tests simply tell you if you are pregnant or not, but not how much hCG is in the blood sample.
There can be a couple of reasons why you would get a positive urine based pregnancy test but have a negative, not pregnant, blood test result.
Home pregnancy tests, on the market today, can be very, very sensitive. Depending on what brand you are using, there is a possibility that your test picked up a level of hCG that is below what the lab, processing your blood sample, considers a positive result. The typical cut off levels for a positive, blood based, pregnancy test are typically 5, 10 and 25 units of hCG. If your home pregnancy test picked up a hCG level of 10 or less, but the lab considers a 25 unit level a positive test, you will get conflicting results.
Here are a few reasons why there was a discrepancy in your urine and blood test results:
False Positive Home Pregnancy Test
Home pregnancy tests are usually very accurate. There are times when this is not the case though. False positive test results can happen if the user reads the test beyond the time frame specified in the test instructions. The tester erroneously assumes that they received a positive pregnancy test result, when it was actually a non pregnancy related chemical reaction that was occurring beyond the testing time frame. In rare cases, an extremely rare form of cancer can cause a positive result on your pregnancy test as can some medications.
Qualitative and Quantitative Pregnancy Blood Test Results
For both types of blood tests, the results may negative, even if you are pregnant, if your blood was drawn too early and your hCG level was below what the lab considered a positive result. You can also get a negative result if the lab did not process the sample correctly.
With the quantitative blood test, an ectopic pregnancy or a miscarriage could be the cause of lower than normal hCG levels. Further testing by your doctor can determine if either of these issues could be the cause of a negative blood test.