Total T3 measures all triiodothyronine in the blood, both bound and free.
- Normal range (adults)
- 80–220 ng/dL (1.23–3.4 nmol/L)
- Sample
- Blood
- Fasting
- Not usually needed
- Also called
- T3, Triiodothyronine, Total Triiodothyronine, TT3, Serum T3
Total T3 normal range
| Group | ng/dLConventional units: US, South Asia | nmol/LSI units: UK, Europe, Australia, international |
|---|---|---|
| Adults | 80–220 | 1.23–3.4 |
Your report may use either unit system; labs in the Gulf often print both. Ranges also vary slightly between laboratories, so the range printed on your own report is the one to go by.
Why is the Total T3 test done?
It is mainly used to assess an overactive thyroid.
What does a high Total T3 level mean?
High Total T3 usually points to an overactive thyroid or excess thyroid medicine.
Common causes
- Graves' disease
- Toxic nodules
- Pregnancy or estrogen use
- Excess T3 medicine
Diet and lifestyle tips
- Avoid iodine supplements
- Limit caffeine
- Calcium and vitamin D for bone health
What does a low Total T3 level mean?
Low Total T3 is often the body's response to illness or fasting rather than thyroid disease itself.
Common causes
- Acute or chronic illness
- Fasting or very low-calorie diets
- Hypothyroidism
Diet and lifestyle tips
- Eat enough calories and protein
- Avoid crash diets
When should you see a doctor?
Total T3 alone is not used to diagnose an underactive thyroid; discuss results with your doctor alongside TSH.
Last updated
This page is for general education and is not a diagnosis. Normal ranges differ between laboratories, so always compare your result with the reference range printed on your own report, and discuss abnormal results with your doctor.