Normal thyroid-stimulating hormone (TSH) levels generally fall between 0.5 and 5.0 milliunits per liter (mU/L). If your TSH level is higher than 5.0 mU/L it suggests an underactive thyroid ...

Historically, the "quality" of a serum TSH method has been determined from a clinical benchmark - the assay's ability to discriminate euthyroid levels (~ 0.4 to 4.0 mIU/L) from the profoundly low ...