What thyroid labs should I ask for?
If the only thyroid number you got back was TSH, you may still be missing useful context. A fuller panel can surface things TSH alone won't catch.
TSH (thyroid stimulating hormone) is the standard screening test, but it is a pituitary signal, not a thyroid hormone. It reflects how the brain is signaling the thyroid rather than showing the full hormone picture directly. That is one reason some patients with fatigue, weight gain, hair loss, brain fog, or cold intolerance are told their labs are normal based on TSH alone.
A fuller workup usually includes Free T3, Free T4, Reverse T3, and thyroid antibodies like Anti-TPO and Anti-Thyroglobulin. Together those give a broader view of production, conversion, and whether autoimmune activity is involved.
Some clinicians work with narrower targets than the standard lab reference range. Many labs still mark TSH as normal up to about 4.5 to 5.0, while some practitioners prefer to see it lower. Free T3 tends to get interpreted in the context of symptoms rather than by range cutoff alone. That's why people can be told everything looks normal and still feel very much not normal.
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Frequently asked questions
Is TSH enough to check my thyroid?
For a basic screen, maybe. But it often misses things. A fuller thyroid panel usually includes TSH, Free T3, Free T4, Reverse T3, and thyroid antibodies such as Anti-TPO and Anti-Thyroglobulin — especially if you have symptoms that a normal TSH doesn't explain.
What is Reverse T3 and why does it matter?
Reverse T3 is an inactive form of T3. During stress, illness, or caloric restriction, the body may convert more T4 into Reverse T3 instead of active T3. In the right context, that can help explain ongoing symptoms even when TSH does not look alarming.
Can I order thyroid labs without a doctor?
In most US states, yes. Direct-to-consumer lab companies and third-party ordering services often let you order thyroid panels yourself. LabLooker helps compare prices across providers.
How often should I retest thyroid levels?
If you are starting thyroid medication or adjusting a dose, retesting every 6 to 8 weeks is common until levels are stable. After that, many people recheck every 3 to 6 months. If this is your first thyroid workup, a comprehensive panel can serve as a baseline.