Why do you have to wait three months to get retested for chlamydia?

Test says pos.: The test for chlamydia can stay positive for a while even after you are treated. That is the reason to wait to be retested.

Check reinfection: With recommended treatments for chlamydia (azithromycin or doxyccyline), treatment failure is very rare. Retesting is designed mostly to check for reinfection, which is present in 10-15% of people retested within 3 months. If an atypical treatment is used, or if the patient may have not completed treatment, an earlier test for treatment failure can be done after 3-4 weeks after (but no sooner).