What Is a Thyroid Blood Test?

Thyroid blood tests evaluate how well your thyroid gland is functioning.

Common Thyroid Tests

• TSH: most sensitive screening test
• Free T4: main hormone produced by thyroid
• Free T3: active hormone
• Anti-TPO antibodies: Hashimoto's
• TSI: Graves' disease

Typical Panel

• TSH + free T4 for basic screening
• Add free T3 and antibodies for full evaluation

When to Test

• Symptoms of hypo/hyperthyroidism
• Family history
• Pregnancy
• Monitoring medication