Triiodothyronine (T3)
Private Triiodothyronine (T3) testing in London for £88, measuring one total thyroid hormone marker with results expected in around 1 day.
Turnaround time
1 business days
Biomarkers count
1
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Overview of the Triiodothyronine Test
The Triiodothyronine blood test measures Total T3, one of the principal thyroid hormones involved in regulating metabolism, energy use and many other physiological processes.
The test assesses 1 thyroid hormone marker: Triiodothyronine (T3).
Triiodothyronine, commonly abbreviated to T3, is the more biologically active of the two main thyroid hormones.
The thyroid gland produces some T3 directly.
A substantial proportion is generated elsewhere in the body by conversion of Thyroxine, or T4, into T3.
Most T3 circulating in the bloodstream is attached to transport proteins.
A smaller proportion circulates unbound as Free T3.
This test measures total Triiodothyronine, meaning both protein-bound and free hormone are included in the result.
That is different from a Free Triiodothyronine test.
Total T3 can be particularly useful when hyperthyroidism or thyrotoxicosis is being investigated.
In some people with thyroid overactivity, T3 becomes elevated before T4 or is disproportionately raised.
T3 can therefore add useful information when TSH is suppressed but other thyroid hormone measurements are less clear.
Total T3 is generally less useful as a standalone marker for hypothyroidism.
T3 concentrations can remain within the expected range despite early or established underactive thyroid function.
Transport proteins can also affect Total T3.
Pregnancy, oestrogen-containing medicines, liver conditions and changes in thyroid-binding proteins can alter total hormone concentrations without necessarily changing the free biologically active fraction.
For this reason, Total T3 is usually interpreted alongside Thyroid Stimulating Hormone, Free T4 and, where appropriate, Free T3.
What Does the Triiodothyronine Test Check?
The test measures the total concentration of Triiodothyronine circulating in the blood, including protein-bound and free T3. This test measures 1 biomarker.
Triiodothyronine (T3)
Measures total circulating T3, including protein-bound and unbound hormone, supporting assessment of thyroid hormone activity and particularly investigation of suspected thyroid overactivity.
Who May Benefit From the Triiodothyronine Test?
Total T3 testing can be useful where thyroid overactivity is suspected or where other thyroid results require additional clarification.
People with a suppressed TSH result - Total T3 can help determine whether circulating thyroid hormone activity is increased.
People undergoing investigation for hyperthyroidism - T3 can be elevated in Graves' disease and other causes of thyroid overactivity.
People with suspected T3-predominant thyrotoxicosis - T3 can occasionally be raised even when T4 remains within range.
People with an abnormal Free T4 result requiring broader thyroid assessment - Total T3 provides additional hormone information.
People with known thyroid disease under specialist monitoring - Repeat measurements may be useful in selected clinical pathways.
People taking thyroid medication under medical supervision - T3 may occasionally be monitored depending on the treatment regimen.
People with previous abnormal Triiodothyronine results - Repeat testing can establish whether the abnormality persists.
People undergoing a comprehensive thyroid profile - Total T3 can complement TSH, Free T4, Free T3 and thyroid antibodies.
How to Prepare
Do not stop prescribed thyroid treatment without clinical advice.
Because this test measures Total T3, changes in hormone-binding proteins can affect the result independently of the free hormone concentration.
Symptoms and Reasons to Consider the Triiodothyronine Test
Changes in T3 can produce symptoms through altered thyroid hormone activity, although symptoms are not specific enough to diagnose thyroid disease alone.
Palpitations or a racing heartbeat - Excess thyroid hormone can increase heart rate and cardiovascular stimulation.
Unexplained weight loss - Hyperthyroidism can increase metabolic activity.
Heat intolerance or increased sweating - Excess thyroid hormone can increase heat production.
Tremor or shakiness - Thyrotoxicosis can increase sympathetic nervous-system activity.
Nervousness or restlessness - Hyperthyroidism can contribute to anxiety-like symptoms.
Frequent bowel movements - Increased gastrointestinal activity can occur with thyroid overactivity.
A suppressed TSH result - Measuring T3 can help clarify the degree and pattern of thyroid hormone excess.
A previous abnormal thyroid hormone result - Repeat testing can provide information about the direction of change.
Symptoms associated with thyroid disease have many alternative causes and should not be interpreted from T3 alone.
Severe palpitations, chest pain, marked breathlessness, confusion or symptoms suggesting severe thyrotoxicosis require prompt medical assessment.
How to Book Your Triiodothyronine Test
The Triiodothyronine test can be booked privately for focused measurement of Total T3.
Choose the Triiodothyronine
Select the individual Triiodothyronine (T3) blood test online.
Select your sample collection option
Choose an in-clinic blood draw or professional home or hotel phlebotomy where suitable.
Attend your appointment
A trained healthcare professional collects the required venous blood sample.
Laboratory analysis
Your serum undergoes laboratory measurement of Triiodothyronine (T3).
Receive your results securely
Your authorised result is delivered securely and can be interpreted alongside TSH, Free T4 and Free T3 where appropriate.
When Will I Receive My Results?
The current London Blood Tests catalogue lists Triiodothyronine (T3) at £88.
The specialist laboratory pathway for Total T3 is typically approximately 1 day after laboratory receipt.
The sample undergoes thyroid hormone analysis, quality-control procedures and result authorisation.
Turnaround begins when the specimen reaches the laboratory rather than necessarily from the exact time of blood collection.
Understanding Your Results
A raised Total T3 result can occur with hyperthyroidism.
The result is particularly useful when TSH is suppressed and thyroid overactivity is suspected.
In some cases, T3 may be elevated disproportionately compared with T4.
A low Total T3 result can occur in several circumstances and does not necessarily mean primary hypothyroidism is present.
Severe illness, calorie restriction and reduced conversion of T4 to T3 can lower circulating T3.
Transport-protein changes can also alter Total T3.
For example, pregnancy or oestrogen treatment can increase thyroid-binding proteins and affect total hormone concentrations.
This is why Total T3 should generally be interpreted alongside TSH and Free T4.
Where binding-protein effects are a concern, Free T3 can provide a different view of circulating hormone activity.
The laboratory's own reference interval should always be used.
Why Book With London Blood Tests?
London Blood Tests provides private Total T3 testing for focused thyroid hormone assessment.
Measures total Triiodothyronine - The test assesses both bound and free circulating T3 together.
Useful in hyperthyroidism assessment - T3 can become elevated during thyroid overactivity.
Can identify T3-predominant patterns - Some people have disproportionately raised T3 despite less marked changes in other thyroid hormones.
Complements TSH and Free T4 - Combined thyroid markers provide more useful information than T3 alone.
Distinct from Free T3 - Total and free Triiodothyronine answer related but different laboratory questions.
Rapid laboratory analysis - The specialist laboratory pathway can typically report Total T3 in around 1 day.
Professional blood collection - Clinic and suitable home or hotel phlebotomy appointments are available.
Clear pricing - The Triiodothyronine test costs £88.
Private Triiodothyronine Blood Test in London
London Blood Tests provides private Triiodothyronine testing for people requiring assessment of Total T3.
The test costs £88 and measures 1 thyroid hormone biomarker: Triiodothyronine (T3).
Laboratory results are typically expected approximately 1 day after laboratory receipt.
Total T3 is particularly useful during investigation of hyperthyroidism and should normally be interpreted alongside TSH and Free T4.