Blood test for thyroid-stimulating hormone (TSH)
Blood test for free thyroxine (free T4)
Blood test for total T4
Blood test for triiodothyronine (T3), if needed
Thyroid peroxidase antibody (TPOAb) test
Thyroglobulin antibody test, if needed
Repeat thyroid blood tests to confirm abnormal results
Review of symptoms and medical history
Physical examination of the thyroid gland
Thyroid ultrasound, if a goiter or nodules are present
Pituitary hormone testing, if central hypothyroidism is suspected