What is the normal range of T4 in adults?

Normal levels in adults. In adults, normal levels of total T4 range from 5–12 micrograms per deciliter (mcg/dl) of blood. Normal levels of free T4 range from 0.8–1.8 nanograms per deciliter (ng/dl) of blood. Normal T4 levels also vary across trimesters of pregnancy. A 2011 study in the Journal of Thyroid Research outlines
What does it mean if your T4 level is low?
Low levels of any of these tests (total T4, free T4, or free T4 index) may indicate an underactive thyroid, also known as hypothyroidism. If your T4 test results are not normal, your health care provider will likely order more thyroid tests to help make a diagnosis. These may include: T3 thyroid hormone tests.
What is the difference between free T4 and Total T4?
A total T4 test detects levels of both bound and free T4, while a free T4 test only identifies free T4 levels. A healthcare provider may also recommend a TSH test to assess thyroid function. Combining a free T4 test with a TSH test gives the most accurate insight into how the thyroid is functioning.

What does a high free T4 index mean?

The free T4 index includes a formula that compares free and bound T4. High levels of any of these tests (total T4, free T4, or free T4 index) may indicate an overactive thyroid, also known as hyperthyroidism.

What does it mean if my T4 level is low?
T4 levels exist within a normal range. Hypothyroidism is where the thyroid produces too little thyroid hormone, which results in lower-than-normal T4 levels. In people with hyperthyroidism, the…
Can cytomel cause low free T4 levels?
Taking T3 only thyroid medication like Cytomel or liothyronine will cause your free T4 to drop below the "normal" range completely and even flag as low. This has to do with the fact that you are suppressing the TSH with the T3 and so endogenous production of T4 decreased dramatically.