Let’s explore “Free T4 — lab reference”

Binding abnormalities and severe illness may affect some free-hormone assays.

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

Affected by thyroid-binding globulin, pregnancy, estrogen, and medications.

Mayo example age 20-24: M 5.25-20.7; F <0.13-1.08. Declines with age and is method-dependent.

Often used when total PSA is in an indeterminate zone. Ask your clinician to use the performing-lab risk table.

How you sit or lie down for the sample, and stress during collection, can affect this result. Use the cutoff from the lab that ran your test.

Your lab may use its own range. Symptoms, medicines, and the types of white blood cells also matter.

Altitude, smoking, hydration, androgen therapy, and pregnancy may shift values.

Ask your clinician to consider altitude and iron/B12/folate status. Pregnancy requires trimester-specific ranges.

Hydration and altitude are major modifiers. Ask your clinician to review alongside hemoglobin and RBC indices.

Macrocytosis and microcytosis require cause-specific interpretation.

The test method matters. Ask your clinician to review with MCV and MCHC.