Estimate the earliest reliable testing date.
After implantation (~9 DPO), hCG doubles every 48 hours. Sensitive tests (10 mIU/mL) may detect pregnancy at 9–10 DPO. Standard tests (25 mIU/mL) are reliable at 12–14 DPO. Testing on the day of your expected period gives ~99% accuracy. Early testing before 10 DPO often yields false negatives.