TSH Test
The single most important first-line thyroid screen — a sensitive check for underactive or overactive thyroid function.
The TSH test is the single most important first-line screen for thyroid health, offering a highly sensitive check for both underactive and overactive thyroid function.
About the TSH Test
Thyroid-Stimulating Hormone (TSH) is produced by the pituitary gland to regulate your thyroid. Because it responds sensitively to even small changes in thyroid activity, TSH is the preferred first test for detecting thyroid disorders. A raised TSH typically suggests an underactive thyroid, while a low level suggests an overactive one, prompting further hormone testing where needed.
Preparation and turnaround
A quick venous blood sample is taken with no fasting required, though a morning sample is often preferred. Results are usually available within one to two working days. If your TSH is abnormal, your doctor may recommend a full Thyroid Function Test to clarify the picture.
Frequently asked questions
What does a high TSH mean?
A raised TSH usually indicates an underactive thyroid (hypothyroidism), while a low TSH suggests an overactive thyroid (hyperthyroidism).
Is TSH enough on its own?
TSH is an excellent first-line screen. If it is abnormal, T3 and T4 are usually added to complete the assessment.
Do I need to fast?
No fasting is required, though testing in the morning is often preferred.
Some tests require fasting. We'll confirm any preparation (such as fasting for 8–10 hours) when we confirm your appointment. When in doubt, ask us at booking.
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