What is a full thyroid panel?

Typically TSH, Free T4, Free T3, and thyroid antibodies (TPO and thyroglobulin). Some practitioners add markers like reverse T3 for additional context.

Can my TSH be normal and my thyroid still be off?

TSH is a screening marker, and it's possible for TSH to sit in range while other markers — free hormones or antibodies — show something worth attention. That's the argument for a complete panel when symptoms persist.

What do thyroid antibodies mean?

Elevated TPO or thyroglobulin antibodies indicate immune activity directed at the thyroid, associated with autoimmune thyroid conditions like Hashimoto's. Interpretation and next steps belong with your healthcare provider.

Do I need to fast for thyroid blood tests?

Fasting isn't generally required for thyroid markers, though timing and biotin supplements can influence results — follow your lab's and practitioner's instructions.

Thyroid Blood Tests, Explained

Most people's only thyroid test has been a single TSH at an annual physical. TSH is a genuinely useful screening marker — but it's one gauge on a dashboard. Here's what a fuller panel includes and what each piece shows.

TSH (thyroid-stimulating hormone)

TSH comes from the pituitary gland and tells the thyroid how hard to work. High TSH generally suggests the thyroid is underperforming (the pituitary is shouting); low TSH suggests overactivity. It's the standard first-line marker — and also the reason a “normal” result can feel unsatisfying, since it measures the signal to the thyroid rather than the hormones themselves.

Free T4 and Free T3

T4 is the thyroid's main output; T3 is the more active form your body converts it into. The “free” versions measure hormone that's actually available to your cells. Together with TSH, they show not just whether the system is being pushed, but what it's producing — and whether conversion from T4 to T3 appears adequate.

Thyroid antibodies (TPO and thyroglobulin)

Antibody testing looks for immune activity directed at the thyroid. Elevated thyroid peroxidase (TPO) or thyroglobulin antibodies are associated with autoimmune thyroid conditions such as Hashimoto's — the most common driver of underactive thyroid in the United States. Antibodies can be elevated years before hormone levels shift, which is why practitioners investigating symptoms often include them rather than waiting.

Sometimes added

Some practitioners also look at reverse T3 and related markers for a fuller conversion picture; views differ across conventional and functional medicine on how much these add, and your practitioner can explain their reasoning either way.

The takeaway

If thyroid symptoms are on the table, the informative move is a complete panel — TSH, Free T4, Free T3, and antibodies — reviewed by someone who looks at the pattern, not a single number in isolation.