Abnormal free T4 levels can have various causes, just like most other symptoms. Finding the true cause means ruling out or confirming each possibility – in other words, diagnosis.
Diagnosis is usually a complex process due to the sheer number of possible causes and related symptoms. In order to diagnose abnormal free T4 levels, we could:
T4 (Free). Unit: ng/dL [pmol/L]
Possible responses:→ Don't know
→ Under 0.4  (very low)
→ 0.4 to 0.8 [5-10] (low)
→ 0.9 to 2.0 [11-26] (normal)
→ Over 2.0  (elevated)