t4 (eclia)
ThyroidBlood sampleResults 24 hrsNo fasting
T4 (ECLIA)
T4 (Thyroxine) is the main hormone produced by the thyroid gland and a key marker of how well your thyroid is working. High levels can suggest an overactive thyroid (hyperthyroidism), while low levels can point to an underactive thyroid (hypothyroidism).
Sample
Blood
Results
24 hrs
Fasting
Not required
Follow-up
Optional add-on
What this test detects
Total T4
ECLIA · serum
Quantitative (µg/dL)
When to get this test
Suspected hypo- or hyperthyroidism
Helps assess whether the thyroid is underactive or overactive, usually together with TSH.
Goiter or neck swelling
Useful when there is enlargement of the thyroid or a lump in the neck.
Fatigue or weight changes
Supports evaluation of tiredness, unexplained weight gain or loss, and other symptoms that may be thyroid-related.
How to prepare
01
No special preparation needed.
02
If you take thyroid medication, ask whether to take it before or after the draw.
Common questions
Do I need to fast before a T4 test?
No, fasting is not required. You can eat and drink as usual before your test.
What is the difference between T4 and TSH?
T4 is the hormone made by your thyroid, while TSH is the signal from your brain that controls how much hormone the thyroid releases. Checking both gives a clearer picture of thyroid health.
What symptoms might warrant a T4 test?
Symptoms like persistent fatigue, weight changes, neck swelling, feeling unusually hot or cold, or changes in mood may prompt your doctor to check your T4.