What is the normal thyroid level and how does it relate to hyperthyroidism?

Normal labs vary by lab and method, but typically a normal TSH is approximately 0.4–4.0 mIU/L (ranges differ). In primary hyperthyroidism, TSH is suppressed (very low) and free T4 and/or free T3 are high. Because lab ranges vary, your doctor interprets results in context of symptoms and other tests. If only T4 is mildly high but symptoms are strong, further testing (free T3 or antibody tests) may be needed. Don’t self-adjust medication — discuss results with your clinician