HCG can be detected in urine or blood after implantation, which occurs on average 9 daye (range 6-12 days) after fertilization. Some home pregnancy tests claim to detect hCG as early as 4 days before the next expected period. Whether that statement is accurate for an individual woman depends on the length of her luteal phase and on how soon that individual embryo implanted. Quantitative blood (serum beta) tests can detect hCG levels as low as 1 mIU/mL, while urine tests have published detection thresholds between 20 and 100 mIU/mL, depending on the brand. Qualitative blood tests generally have a threshold of 25 mIU/mL, and so are less sensitive than some available home pregnancy tests.