Let’s explore “Total T4 — lab reference”

Useful in selected hyperthyroid states; not a sensitive stand-alone test for hypothyroidism.

No broadly accepted treatment target. Dr. Purser to define whether and how this is used.

The test method matters. Positive result supports thyroid autoimmunity but does not determine treatment alone.

The test method matters. Also affects thyroglobulin tumor-marker interpretation.

Ask your clinician to use the exact assay cutoff. Helpful in selected Graves disease questions.

This is not a general thyroid wellness target. It may be used for follow-up after certain thyroid conditions, alongside thyroid anatomy and antibody results.

Morning fasting collection is preferred when practical. Day-to-day variation is substantial.

Negative acute-phase reactant; affected by liver function and nutrition.

Calculated from iron and TIBC. Fasting and timing improve consistency.

Acute-phase reactant. Menstruation, menopause, inflammation, liver disease, and iron therapy matter.

<150 supports deficiency; 150-400 is often treated as borderline and may warrant MMA/homocysteine review.

<4.0 suggests deficiency. Recent intake or supplementation may raise serum values.