Progesterone's time to take effect depends on the form used and the purpose. Generally, for triggering a period, progesterone treatment is typically evaluated after about two weeks, with bleeding usually occurring 2-5 days after stopping progesterone if pregnancy has not occurred. For menopausal symptom relief via hormone replacement therapy (HRT) containing progesterone, it can take up to 3 months to fully see the effects. Progesterone creams may take several months to improve symptoms. Peak blood levels after administration vary by form, such as about 3 hours for oral capsules and up to 24 hours for vaginal inserts. Key timelines:

• Period triggering: about 2 weeks to see if a period occurs after progesterone treatment, bleeding 2-5 days after stopping.
• Menopausal symptom relief (HRT): up to 3 months for full effect.
• Progesterone creams: several months for symptom improvement.
• Peak blood levels after doses: oral capsules ~3 hours, injections ~8 hours, vaginal gels 3.5-7 hours, vaginal inserts 17-24 hours.

Thus, the effect onset depends largely on the specific use and administration method.