FT4 normal range — check your value

Roughly 0.8 to 1.8 ng/dL, with the exact range depending on the lab's method.

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Your FT4 test value

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FT4

ng/dL

What FT4 measures

The unbound form of thyroxine, the main hormone the thyroid produces before it is converted to T3.

FT4 normal range chart

ResultFT4 (ng/dL)

Below rangeBelow 0.93

In range0.93 – 1.7

Above range1.7 and above

These bands are for female, 31–45 years. Enter your age and gender above to see the bands for you. The table below shows the range for every age and gender.

FT4 normal range by age and gender

AgeMaleFemale

0–1 years0.9 – 2.2 ng/dL0.9 – 2.2 ng/dL

2–6 years0.9 – 1.9 ng/dL0.9 – 1.9 ng/dL

7–11 years0.9 – 1.8 ng/dL0.9 – 1.8 ng/dL

12–17 years0.8 – 1.8 ng/dL0.8 – 1.7 ng/dL

18–30 years0.93 – 1.7 ng/dL0.93 – 1.7 ng/dL

31–45 years0.93 – 1.7 ng/dL0.93 – 1.7 ng/dL

46–60 years0.93 – 1.7 ng/dL0.93 – 1.7 ng/dL

60 years and above0.93 – 1.7 ng/dL0.8 – 1.8 ng/dL

What a high FT4 means, and common causes

The main thyroid hormone is above range, which with a low TSH confirms an overactive thyroid.

Common causes: Graves' disease, toxic nodule, thyroiditis releasing stored hormone, and too high a dose of thyroid medication.

What a low FT4 means, and common causes

Free T4 below range with a high TSH confirms an underactive thyroid that needs treatment.

Common causes: Hashimoto's thyroiditis, iodine deficiency, after thyroid surgery or radioiodine, pituitary disease, and some medicines.

Frequently asked questions

Roughly 0.8 to 1.8 ng/dL, with the exact range depending on the lab's method.

Total T4 includes hormone bound to carrier proteins, which pregnancy and some medicines change. Free T4 measures only the active, unbound fraction, so it is more reliable.

Not entirely. In subclinical hypothyroidism TSH is raised while Free T4 is still normal, which is why both are tested together.

Thakan, wazan badhna, kabz aur sust mehsoos hona aam hai. Yeh hypothyroidism ki pushti karta hai aur ilaaj se theek ho jaata hai.

Please note. This page explains what a number means against reference ranges for your age and gender. It does not diagnose anything, cannot see the rest of your report, and is no substitute for a doctor. If your lab’s printed range differs, your lab’s range applies.