Side effects associated with the use of Unithroid include the possibility of stomach cramping, anxiousness, changes in eating patterns, menstrual cycle changes, pain in the chest, emotional issues, being tired, loss of hair, diarrhea, racing heart, weakness in the muscles, palpitations of the heart, insomnia, vomiting, weight loss, fever, sweating or heart attack. Other side effects associated with the use of Unithroid could include a preliminary loss of hair and headaches. Allergic reactions may occur with the side effects being characterized by an outbreak of hives, itching of the skin, swelling of the maxofacial area or collapsing of the airway. If this occurs, medical attention should be sought at once.