Thyroid
T3 Total (Total Triiodothyronine)
Thyroid
Total T3 including protein-bound. Useful when binding proteins may be abnormal.
VAT-exempt medical service
Total T3 (TT3) measures the combined amount of protein-bound and free triiodothyronine circulating in your blood. T3 is produced directly by the thyroid gland and through conversion of T4 in peripheral tissues. Together with T4 and TSH, T3 plays a central role in regulating metabolism, heart rate, and body temperature. Total T3 is a valuable component of a complete thyroid panel and should always be interpreted alongside other thyroid markers.
Total T3 testing adds depth to a thyroid evaluation, especially when combined with TSH, Free T4, and Free T3. It helps detect hyperthyroidism, assess thyroid hormone production, and monitor treatment response. It is particularly useful when investigating symptoms of thyroid imbalance that persist despite apparently normal TSH and T4 values.
What a high value can mean
Elevated Total T3 suggests overproduction of thyroid hormone, commonly seen in hyperthyroidism. It may also be associated with iodine deficiency, Graves' disease, or thyroid nodules. Pregnancy and oestrogen-containing medications can raise total T3 by increasing binding proteins, so results should be interpreted in clinical context.
What a low value can mean
Low Total T3 can indicate hypothyroidism or impaired conversion of T4 to T3. Contributing factors include Hashimoto's thyroiditis, calorie restriction, low-carbohydrate diets, chronic stress, insulin resistance, and deficiencies in iodine, selenium, zinc, iron, and B vitamins. Certain supplements and medications may also lower T3 levels.
No preparation is needed before the test. Do not take thyroid medication until after the blood draw. Test before 10 am for consistent results. Avoid vigorous exercise on the morning of the test. Bring valid identification. If you take a supplement containing biotin (often sold for hair and nails), pause it for two days before the test, as high doses can distort the result.
Order your test
Choose your test and pay online. Your lab referral is created straight away.
Give your sample
Visit any of our partner sampling locations. No appointment needed at most of them.
The lab analyses it
Your sample is analysed at an accredited Swedish laboratory.
Get your results
Your values appear in your account with reference ranges and an explanation of each marker.
Total T3 measures both the protein-bound and unbound fractions of T3, while Free T3 measures only the unbound, active fraction. Free T3 more directly reflects hormone activity at the cellular level, but Total T3 provides useful additional context, especially when binding protein levels may be altered.
Yes. Chronic stress triggers the body to convert more T4 into reverse T3 instead of active T3, which can reduce both Total T3 and Free T3 levels. This is part of the body's adaptive response to conserve energy.
Fasting is not required, but it is best to avoid exercise on the morning of the test and to have your blood drawn before 10 am for the most reliable results.