Thyroxine (Total)
Private Thyroxine (Total) testing in London for £68, measuring one total thyroid hormone marker with results expected in around 1 day.
Turnaround time
1 business day
Biomarkers count
1
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Overview of the Thyroxine (Total) Test
The Thyroxine (Total) blood test measures the total concentration of Thyroxine, or T4, circulating in the bloodstream.
The test assesses 1 thyroid hormone marker: Thyroxine (T4).
Thyroxine is the principal hormone secreted by the thyroid gland.
It plays a central role in regulating metabolism and also acts as the main circulating precursor from which the more biologically active hormone Triiodothyronine, or T3, is produced.
Most T4 in the bloodstream is attached to transport proteins.
These include thyroxine-binding globulin, transthyretin and Albumin.
Only a small proportion circulates as unbound Free T4.
The Total T4 result therefore includes both protein-bound and free hormone.
This is an important distinction from Free Thyroxine testing.
Changes in thyroid-binding proteins can alter Total T4 even when biologically available Free T4 remains normal.
Pregnancy and oestrogen-containing medication can increase thyroid-binding globulin and therefore increase Total T4.
Certain illnesses, liver conditions, protein abnormalities and medicines can also change binding proteins.
For this reason, Total T4 usually requires interpretation alongside Thyroid Stimulating Hormone and, where appropriate, Free T4.
A high Total T4 can occur with hyperthyroidism but can also result from increased thyroid-binding proteins.
A low result can occur with hypothyroidism or reduced binding proteins.
The pattern across TSH, Free T4 and clinical symptoms is generally more informative than Total T4 considered alone.
What Does the Thyroxine (Total) Test Check?
The test measures the combined amount of protein-bound and unbound Thyroxine circulating in the blood. This test measures 1 biomarker.
Thyroxine (T4)
Measures total circulating Thyroxine, including both protein-bound and free T4, supporting assessment of thyroid hormone status when interpreted alongside TSH and binding-protein effects.
Who May Benefit From the Thyroxine (Total) Test?
Total T4 can provide useful thyroid information where a clinician specifically wants to assess overall circulating Thyroxine.
People undergoing investigation of abnormal thyroid function - Total T4 can contribute to a broader assessment of thyroid hormone status.
People with an abnormal Thyroid Stimulating Hormone result - Additional thyroid hormone measurement can clarify the biochemical pattern.
People with suspected hyperthyroidism - Total T4 can become elevated with increased thyroid hormone production.
People with suspected hypothyroidism - Total T4 can be reduced in underactive thyroid disease.
People with a previous abnormal Total T4 result - Repeat measurement can establish whether the change persists.
People undergoing specialist thyroid assessment - Total T4 can provide complementary information where binding proteins are also being considered.
People taking thyroid hormone treatment under clinical supervision - Selected monitoring pathways may include Total T4.
People requiring comparison with historical Total T4 results - Using the same type of hormone measurement can support longitudinal comparison.
How to Prepare
Do not stop thyroid or hormonal medication solely to alter the laboratory result.
Total T4 should be interpreted with awareness of pregnancy, oestrogen therapy and other factors that can affect thyroid-binding proteins.
Symptoms and Reasons to Consider the Thyroxine (Total) Test
Changes in thyroid hormone activity can affect energy, metabolism, cardiovascular function, temperature regulation and reproductive health.
Persistent fatigue or low energy - Reduced thyroid hormone activity can contribute to tiredness.
Unexplained weight gain - Hypothyroidism can reduce metabolic activity.
Unexplained weight loss - Hyperthyroidism can increase metabolic rate.
Cold intolerance - Feeling unusually cold can occur with hypothyroidism.
Heat intolerance or excessive sweating - Excess thyroid hormone can increase heat production.
Palpitations or a racing heartbeat - Thyroid overactivity can affect cardiovascular function.
Hair thinning or skin changes - Both underactive and overactive thyroid states can affect hair and skin.
A previous abnormal TSH result - Total T4 can provide additional hormone information.
Total T4 can be affected by thyroid-binding proteins as well as thyroid hormone production.
An abnormal Total T4 does not automatically mean the biologically active hormone level is abnormal.
Free T4 and TSH are often required for more complete interpretation.
How to Book Your Thyroxine (Total) Test
The Thyroxine (Total) test can be booked privately for focused measurement of circulating Total T4.
Choose the Thyroxine (Total)
Select the individual Total T4 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 Thyroxine (T4).
Receive your results securely
Your authorised result is delivered securely and can be interpreted alongside TSH and Free T4 where appropriate.
When Will I Receive My Results?
The specialist laboratory turnaround for Thyroxine (Total) is approximately 1 day after laboratory receipt.
Total T4 is a routinely available endocrine assay.
The sample undergoes laboratory hormone measurement, quality-control procedures and result authorisation.
Turnaround begins when the specimen reaches the laboratory rather than necessarily from the exact time the blood sample is collected.
Understanding Your Results
A raised Total T4 result can occur with hyperthyroidism.
However, an elevated result can also occur when thyroid-binding proteins are increased, including during pregnancy or with oestrogen-containing medication.
A low Total T4 result can occur with hypothyroidism but may also reflect reduced concentrations of thyroid-binding proteins.
This is why Total T4 should not usually be interpreted without TSH and, where necessary, Free T4.
In primary hypothyroidism, TSH is generally elevated as thyroid hormone production falls.
In primary hyperthyroidism, TSH is commonly suppressed as thyroid hormone levels rise.
Free T4 is less affected by changes in binding proteins and can therefore provide a more direct assessment of biologically available Thyroxine.
The laboratory's own validated reference interval should always be used.
Why Book With London Blood Tests?
London Blood Tests provides private Total T4 testing for focused assessment of circulating Thyroxine.
Measures total circulating T4 - The assay includes both bound and unbound Thyroxine.
Useful in broader thyroid assessment - Total T4 can complement TSH and Free T4.
Relevant to hyperthyroid and hypothyroid patterns - Abnormal production can change Total T4 concentrations.
Provides historical comparability - Total T4 may be useful where previous monitoring has used the same marker.
Can highlight binding-protein effects - Total T4 differs from Free T4 and can be influenced by pregnancy or oestrogen treatment.
Rapid laboratory turnaround - Results are expected approximately 1 day after laboratory receipt.
Professional blood collection - Clinic and suitable home or hotel phlebotomy appointments are available.
Clear pricing - The Thyroxine (Total) test costs £68.
Private Thyroxine (Total) Blood Test in London
London Blood Tests provides private Thyroxine (Total) testing for people requiring measurement of total circulating T4.
The test costs £68 and assesses 1 thyroid hormone biomarker.
Results are expected approximately 1 day after laboratory receipt.
Total T4 is most informative when interpreted alongside TSH, Free T4 and factors that can alter thyroid-binding proteins.