A healthy result should fall into the range 1.2 - 4.3 Units.

The T7 Index is the product of T4 x T3 Uptake, divided by 100. it is also known as the Free Thyroxine Index.

T7= (T4 x T3-Uptake)/100

This calculation is an attempt to correct for variations in thyroxine binding proteins.

Result interpretation:

Disorder Total T4 T3 Uptake T7
Primary hypothyroid Decreased Decreased Decreased
Secondary hypothyroid Decreased Decreased Decreased
Hyperthyroid Increased Increased Increased
T3 Toxicosis Normal Normal Normal


Reference ranges:

  • males: 1.22 - 4.86
  • females: 0.99 - 4.71

T7 Index result calculator

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