Quick answer
A thyroid profile measures T3, T4 and TSH. Normal TSH is about 0.4–4.5 µIU/mL. High TSH with low T4 means an underactive thyroid (hypothyroidism); low TSH with high T3/T4 means an overactive thyroid (hyperthyroidism). No fasting is needed.
What do T3, T4 and TSH measure?
- TSH (Thyroid Stimulating Hormone) — made by the pituitary gland; it tells the thyroid how much hormone to make. It is the most sensitive marker.
- T4 (Thyroxine) — the main hormone produced by the thyroid.
- T3 (Triiodothyronine) — the active hormone that controls metabolism.
Normal ranges
| Hormone | Typical adult range |
|---|---|
| TSH | 0.4–4.5 µIU/mL |
| Total T4 | 5.0–12.0 µg/dL |
| Total T3 | 80–200 ng/dL |
How to read your thyroid report
| TSH | T3 / T4 | Likely meaning |
|---|---|---|
| High | Low | Hypothyroidism (underactive) |
| High | Normal | Subclinical hypothyroidism |
| Low | High | Hyperthyroidism (overactive) |
| Low | Normal | Subclinical hyperthyroidism |
| Normal | Normal | Normal thyroid function |
Preparation tips
- No fasting needed.
- Give the sample in the morning before your thyroid tablet.
- Tell the doctor if you take biotin supplements.
- Recheck 6–8 weeks after a dose change.
Frequently asked questions
Is TSH alone enough to check thyroid?
TSH is a good screening test, but T3 and T4 help confirm the type and severity of a thyroid problem.
Can thyroid cause weight gain?
Yes. An underactive thyroid slows metabolism and can cause weight gain, tiredness and feeling cold.
Medical disclaimer: This information is for general awareness only and is not a substitute for professional medical advice. Please consult a qualified doctor to interpret your results and before starting or changing any treatment.