Yes, sleeping with a menstrual cup is generally considered appropriate for overnight wear when used as directed, which is up to 12 hours for most brands. That makes them a popular overnight option since you can insert before bed and empty in the morning. Always follow the specific instructions that came with your cup, since wear time and care vary by brand. If you're worried about leaks on heavy nights, you can layer with period underwear or an overnight pad for backup. Rael makes organic cotton overnight pads and period underwear if you want that extra peace of mind. If you ever feel unwell while using any internal product, take it out and check in with your doctor.