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Free T4, Free4.
A reflex test for thyroid function to assist in diagnosing hyperthyroidism and hypothyroidism in the presence of an abnormal TSH level.
Serum collected in a gold-, red-, or red/gray-top tube. Plasma collected in a green-top (heparin) tube is also acceptable.
|Age||Conventional Units||SI Units (Conventional Units × 12.9)|
|Newborn||0.8–2.8 ng/dL||10–36 pmol/L|
|1–12 mo||0.8–2 ng/dL||10–26 pmol/L|
|1–18 yr||0.8–1.7 ng/dL||10–22 pmol/L|
|Adult–older adult||0.8–1.5 ng/dL||10–19 pmol/L|
|Pregnancy||0.7–1.4 ng/dL||9–18 pmol/L|