The most accurate time to take a pregnancy test is generally from the first day of a missed period. For higher accuracy, waiting about a week after the missed period is recommended. Pregnancy tests work by detecting the hormone hCG, which only rises to detectable levels some days after conception and implantation. Key points:

• A pregnancy test can typically detect pregnancy about 9 to 10 days after intercourse or ovulation, roughly corresponding to the time a period is missed or just after.

• Some highly sensitive tests can be used as early as 4 to 6 days before the expected period, but results before the missed period may be less reliable and require retesting later.

• For the most reliable results, waiting about 1 to 2 weeks after the missed period is advised, as this allows hCG levels to build up sufficiently.

• If the menstrual cycle is irregular or uncertain, it is best to wait at least 21 days after unprotected sex before testing.

• Testing too early can give a false negative due to low hCG levels despite pregnancy.

In summary, the best approach is to take a pregnancy test from the first day of a missed period, and for more certainty, wait about a week after that missed period to avoid false negatives. If the test is done too early, it is advisable to repeat it a few days later for confirmation. This guidance balances accuracy with early detection options using modern sensitive pregnancy tests. Let me know if more details on specific types of tests or how to interpret results are needed.