Possible side effects when you buy Ceftin may include diarrhea that is watery or bloody; fever, chills, body aches, flu symptoms; chest pain, fast or pounding heartbeats; unusual bleeding; blood in your urine; seizure (convulsions); pale or yellowed skin, dark colored urine, fever, disorientation or feebleness; jaundice (yellowing of the skin or eyes); fever, sore throat, and headache with a severe blistering, peeling, and red skin rash; skin rash, bruising, severe tingling, numbness, pain, muscle weakness; increased thirst, loss of appetite, bloating, weight gain, shortness of breath; or painful or difficult urination, urinating less than usual or not at all, nausea, vomiting, stomachache, moderate diarrhea, gas, upset stomach; cough, stuffy nose; stiff or tight muscles, muscle pain; joint pain or swelling; headache, drowsiness; feeling restless, irritable, or hyperactive; white patches or sores inside your mouth or on your lips; unusual or unpleasant taste in your mouth; mild itching or skin rash; or vaginal itching or discharge.