Thyroid

Free T4

Also known as: FT4

What it means

The main hormone your thyroid produces. Doctors check this alongside TSH to see what your thyroid is actually doing.

Typical normal range

0.8–1.8 ng/dL

Reference ranges vary by lab, age, sex, and pregnancy. Always check the range on your own report.

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Related terms in Thyroid

TSH
A hormone from your brain that tells the thyroid how hard to work. High TSH = thyroid is sluggish (hypothyroid). Low TSH = overactive (hyperthyroid).

Sources & Standards

The plain-language explanations above draw on published standards from the following bodies. Reference ranges and thresholds vary slightly by lab and demographic — always check the range on your own report and follow your doctor's interpretation.

World Health Organization (WHO)
Global public-health authority
Global reference ranges and disease classifications.
Indian Council of Medical Research (ICMR)
India's apex biomedical research body
India-specific clinical guidelines and reference values.
National Accreditation Board for Testing and Calibration Laboratories (NABL)
India's lab-accreditation authority
Reference-range framework used by accredited Indian labs.
NIH / MedlinePlus
US National Institutes of Health patient-education arm
Plain-language descriptions of tests, conditions, and medicines.

AI can be wrong. Explanations here are for comprehension only — confirm every decision with your doctor.

This is a plain-language explanation for patients, not clinical advice. AI can be wrong. Always confirm with your doctor.