The normal, healthy range of a thyroid test result should be between 0.4 and 4.0 milli-international units per liter, states the National Institutes of Health's Medline Plus. The thyroid level is tested by submitting a sample of the patient's blood to a lab.
Before a thyroid test can be completed, some medications should be avoided temporarily. These medications include Amiodarone, Prednisone, Potassium iodide, Dopamine and Lithium. If a patient's thyroid level comes back higher than normal, it means he may be suffering from an underactive thyroid gland and if it comes back lower than normal, it means he may be suffering from an overactive thyroid gland.