Total T4 measures the total amount of thyroxine in the blood, including both protein-bound and free forms. Thyroxine is the primary hormone released by the thyroid gland.
Category: Thyroid Panel
Also known as: total t4, t4, thyroxine, thyroxine total
Reference range: 5–12 µg/dL (Source: ABIM)
Standard unit: µg/dL
High values may indicate
High total T4 may indicate hyperthyroidism, Graves' disease, thyroiditis, or elevated thyroid-binding globulin (e.g., from pregnancy or estrogen use).
Low values may indicate
Low total T4 may indicate hypothyroidism, pituitary insufficiency, severe illness, or decreased thyroid-binding globulin.