In North Carolina, by driving on the roads you are obligated to take a breath test at the request of an officer (assuming he has sufficient grounds for the request). If you refuse a test, your license will be revoked immediately for thirty days. It will then be revoked for an additional year for refusing the test. You will not be eligible for a limited privilege until at least six months has passed. That means NO DRIVING FOR SIX MONTHS! You should consider refusing a breath test if 1. You feel like you will blow extremely high (a result over .15 will require you to get an Ignition Interlock); 2. You have been in an accident where someone was hurt or killed; or 3. You have a prior conviction for DWI in the last seven years.
Remember that even if you refuse a breath test, the officer can still take your blood. He/she is allowed to use force to do so.