Thyroiditis is a general term. Clinically, the most common type is subacute thyroiditis, and another is Hashimoto's thyroiditis, which are two different diseases. For subacute thyroiditis, the symptoms include fever, neck pain, and throat discomfort. Generally, the first step is to check thyroid function to see if there is hyperthyroidism or hypothyroidism. The second step is to suggest antibody tests, including anti-thyroid peroxidase antibodies and anti-thyroglobulin antibodies. The third suggestion is to conduct a routine blood test and erythrocyte sedimentation rate. Fourth, a thyroid ultrasound is recommended. If necessary, a thyroid fine-needle aspiration may be performed for a definitive diagnosis. If it's Hashimoto's thyroiditis, which is an autoimmune disease, a specific antibody, TPOAB or anti-thyroid peroxidase antibody, is used for diagnosis.