What level is considered hypothyroidism?

Hypothyroidism is typically diagnosed when a person's thyroid-stimulating hormone (TSH) level is above 4.0 milli-international units per liter (mIU/L). A TSH level between 4.0 and 10.0 mIU/L usually indicates mild to moderate hypothyroidism, while levels above 10.0 mIU/L suggest more severe hypothyroidism. Additionally, low levels of free thyroxine (T4) can further confirm the diagnosis.