"Many home pregnancy tests claim to be able to “answer the question after the very first day of the delay”. Is that really true? The fact is that the test can only provide for an accurate result in case the following two factors are considered:

The HCG level in the examined substance;Sensitivity of that specific test.

The level of this hormone in blood or urine depends on the specific day, following fertilization. In the case of normal uterogestation, the level of HCG is being twice increased every 48-60 hours during the first eight weeks.

Thus, 4-5 days after implantation (i.e. approximately before the due time of the expected period), the HCG content in the blood sample is about 25mIU/ml. It can be detected by an immunoassay (analysis of a blood serum, taken from a vein in special laboratories). In another 1-2 days, the HCG level reaches the same mark (25mIU/ml) in urine, but home pregnancy tests are better to be taken in the morning, when the urine is least attenuated.

Be careful when choosing a test in a drugstore! If the package has a note, saying “sensitivity 20 mIU/ml”, then the test is suitable for early detection of pregnancy (immediately after the delay). Tests, with a note “sensitivity 40 mIU/ml” can be used no sooner than on the 7-9 day after implantation bleeding."