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Thyroid Function

Total Thyroxine (Total T4)

Normal range 5–12 µg/dL (64–154 nmol/L SI). Specimen: Serum.

Also known as: T4.

5–12 µg/dLReference range

Reference range

Conventionalµg/dL
512
SInmol/L
64154
SpecimenSerum
Conventional range5–12 µg/dL
SI range64–154 nmol/L
Conversion factor×12.87 (conventional → SI)
PanelThyroid Function

Convert any Total Thyroxine (Total T4) result between units on the unit converter.

What is the normal range for Total Thyroxine (Total T4)?

The standard teaching reference range for Total Thyroxine (Total T4) is 5–12 µg/dL in conventional units, or 64–154 nmol/L in SI units. This value is measured in serum.

Source: Adult reference values compiled from Pagana & Pagana, Mosby's Diagnostic and Laboratory Test Reference, and Fischbach & Dunning, A Manual of Laboratory and Diagnostic Tests. Reference ranges vary by laboratory, method, age, sex, and population — always use the range printed on the actual result.

Above the range

Common causes of a high Total Thyroxine (Total T4)

  • Hyperthyroidism
  • Pregnancy or estrogen (raises binding protein)

Below the range

Common causes of a low Total Thyroxine (Total T4)

  • Hypothyroidism
  • Low binding proteins

At the bedside

Nursing considerations

  • Affected by protein binding; Free T4 is preferred when binding is altered.

Study aid

Your notes on Total Thyroxine (Total T4)

Same panel

More Thyroid Function tests

Free Thyroxine (Free T4)0.8–1.8 ng/dLFree Triiodothyronine (Free T3)2.3–4.2 pg/mLThyroid Peroxidase Antibody (TPO Ab)< 35 (negative) IU/mLThyroid-Stimulating Hormone (TSH)0.4–4 mIU/LTotal Triiodothyronine (Total T3)80–200 ng/dL