Many people have been successful with using internal birth control, such as an IUD or a NuvaRing®, alongside using a menstrual cup.
Because it's common for some people to experience spotting or daily bleeding while fitted with an IUD, a menstrual cup can be invaluable. A cup, even a small-sized one, should be sufficient to continue to collect the flow for a full 12-hour duration.
If you're thinking about using internal birth control with your menstrual cup, speak with your gynecologist prior to the procedure. Your doctor can trim the IUD strings and make them shorter to minimize the chances of the IUD becoming dislodged.
Get to know where your IUD strings are and their normal length. Monitor them regularly, both during your period and off your period when you aren't wearing a menstrual cup. If the strings suddenly feel longer than normal, it might be a sign that your IUD has migrated and you'll want to check with your doctor.
After your cup is inserted and correctly placed, use a finger to swipe around the rim and make sure the strings are not between the cup and your vaginal wall. The IUD strings should be inside the cup.
Make sure to break the seal/suction of the cup before removing it. If the seal is not broken, there is a chance of dislodging the IUD.
If you're using a contraceptive ring: insert the ring first and then the menstrual cup after.
Again, be sure to speak with your doctor about using a menstrual cup prior to starting any internal birth control methods (or vice versa).