Thyroid
Free T4
Unit: ng/dLID: T002
What This Test Measures
Unbound thyroxine; storage hormone produced by thyroid
Conventional vs. Functional Optimal Range
Conventional "Normal"
0.8-1.8 ng/dLYour doctor says you're "fine" anywhere in this range
Functional Optimal
1.0-1.5 ng/dLThis is where you actually feel great
The gap between these ranges is why you feel terrible with "normal" labs. Conventional medicine waits for disease. Functional medicine optimizes for health.
Gabriel's Take
Free T4 measures the raw material your body must convert to active T3. Being in the upper-middle range (1.0-1.5) ensures adequate substrate for conversion. Low-normal T4 with symptoms suggests production issues, not just "borderline."
When This Test Is High
Hyperthyroidism, thyroiditis, T4 overmedication
When This Test Is Low
Hypothyroidism, poor thyroid production
Related Conditions
Energy regulation, metabolism, body temperature
Recommended Follow-Up
Check Free T3, Reverse T3, and thyroid antibodies