Davis's Lab & Diagnostic Tests

Triiodothyronine, Free

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Free T3, FT3.

Common Use:
A complementary adjunct to evaluate thyroid hormone levels primarily related to hyperthyroidism and to assess causes of hypothyroidism.

Serum collected in a gold-, red-, or red/gray-top tube.

Normal Findings:
(Method: Immunoassay)

AgeConventional UnitsSI Units (Conventional Units × 1.54)
0–3 d2–7.9 pg/mL3.1–12.2 pmol/L
4–30 d2–5.2 pg/mL3.1–8 pmol/L
1–23 mo1.6–6.4 pg/mL2.5–9.9 pmol/L
2–6 yr2–6 pg/mL3.1–9.2 pmol/L
7–17 yr2.9–5.1 pg/mL4.5–7.8 pmol/L
Adults and older adults2.6–4.8 pg/mL4–7.4 pmol/L
Pregnant women (4–9 mo gestation)2–3.4 pg/mL3–5.2 pmol/L

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