Do I need a full panel or just TSH?

Often TSH alone is the starting point; further tests are added if it is abnormal or symptoms suggest a problem.

How often should thyroid tests be repeated?

It depends on the reason. People taking thyroid medicine are usually retested after dose changes, as advised by their clinician.

Lab test · Thyroid

Thyroid panel (thyroid function tests)

A thyroid panel combines TSH, free T4 and sometimes T3 and antibodies. What each part shows, when a panel is ordered and how results fit together.

Written by LON6EVITY Editorial Team · Last updated 2026-09-29

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What is included

There is no single fixed thyroid panel. NIDDK explains that TSH is usually measured first, with T4 (often free T4) as a common follow-up; T3 and thyroid antibody tests are added depending on the question being asked.

How results fit together

High TSH with low free T4 suggests an underactive thyroid; low TSH with high free T4 or T3 suggests an overactive thyroid. A mildly abnormal TSH with normal free T4 is sometimes called subclinical thyroid disease and is often rechecked. Antibody tests help identify autoimmune causes such as Hashimoto's or Graves' disease.

Before the test

Biotin supplements can interfere with some thyroid assays, and pregnancy and certain medicines change results. Tell the person ordering the test about anything you take.

Factors that can affect the result

Biotin supplements
Pregnancy
Medicines
Acute illness
Time since dose change

Questions people commonly ask

Do I need a full panel or just TSH?: Often TSH alone is the starting point; further tests are added if it is abnormal or symptoms suggest a problem.
How often should thyroid tests be repeated?: It depends on the reason. People taking thyroid medicine are usually retested after dose changes, as advised by their clinician.

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Sources

Thyroid Tests. National Institute of Diabetes and Digestive and Kidney Diseases (NIH).
Thyroxine (T4) Test. MedlinePlus, U.S. National Library of Medicine.
Triiodothyronine (T3) Tests. MedlinePlus, U.S. National Library of Medicine.
Thyroid Antibodies. MedlinePlus, U.S. National Library of Medicine.