Laboratory test
fT4
Other names and abbreviations: free thyroxine
A hormone produced by the thyroid. It complements TSH in assessing thyroid function.
fT4 to aktywna, „wolna” część tyroksyny. Wynik interpretuje się razem z TSH – to para, która pozwala odróżnić typy zaburzeń tarczycy.
Typical ranges in adults
| Parameter | Typical range | What a deviation may mean |
|---|---|---|
| fT4 | approx. 0.9–1.7 ng/dl (12–22 pmol/l) | the range depends heavily on the laboratory method |
The ranges are approximate and differ between laboratories; they also depend on age, sex and pregnancy. A result outside the range doesn't always mean illness – discuss it with a doctor.
When it is done
With abnormal TSH and when monitoring thyroid treatment.
How to prepare
As with TSH – ideally in the morning, before your dose.
