Nuvaring® may not be effective if: You forget to insert a new ring after the seven day break You remove it at any time for longer than three hours The same ring is left in for more than four weeks Certain medication may interfere with the effectiveness of NuvaRing®. Always ask your doctor if you need extra precautions Some non-prescribed medication, such as St Johns wort (or hypericum), can make NuvaRing® less effective. Check with the pharmacist. Emergency contraception may be required if you do not use NuvaRing® according to instructions, and sexual activity occurred without a condom being used More detailed information about the use of the ring is provided in a booklet included in each NuvaRing® packet.