T3 (Total)
Total triiodothyronine (T3) measures all T3 in blood — both the free, active fraction and the larger fraction bound to carrier proteins. T3 is the more biologically active thyroid hormone, although most circulates in the bound form.
Why it matters: Total T3 can shift when binding-protein levels change (during pregnancy or with certain medications). For evaluating thyroid function specifically, free T3 is often preferred because it reflects what the body's tissues actually use.
May increase with:
May decrease with:
What is T3 (Total)?
Total triiodothyronine (T3) measures all T3 in blood — both the free, active fraction and the larger fraction bound to carrier proteins. T3 is the more biologically active thyroid hormone, although most circulates in the bound form.
What might a high or low T3 (Total) mean?
Total T3 can shift when binding-protein levels change (during pregnancy or with certain medications). For evaluating thyroid function specifically, free T3 is often preferred because it reflects what the body's tissues actually use.
What is the typical reference range for T3 (Total)?
The general-population reference range shown here is 1.3 – 3.1 nmol/L. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.
What can affect T3 (Total)?
It may be higher with: Hyperthyroidism, T3 supplementation. It may be lower with: Hypothyroidism, Chronic illness, Fasting, Selenium deficiency.
Track your T3 (Total) over time
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