Clinicians order Free T3 when thyroid symptoms don’t match other tests, or to monitor therapy that includes liothyronine (T3). It helps assess suspected overactive or underactive thyroid and T4-to-T3 conversion. It’s useful when TSH or Free T4 are borderline but symptoms persist. You can test this marker with Aniva across Germany and Finland.

Clinicians order Free T3 when thyroid symptoms don’t match other tests, or to monitor therapy that includes liothyronine (T3). It helps assess suspected overactive or underactive thyroid and T4-to-T3 conversion. It’s useful when TSH or Free T4 are borderline but symptoms persist. You can test this marker with Aniva across Germany and Finland.

High: May suggest an overactive thyroid, too much T3 medication, or thyroid inflammation. Often reviewed with TSH and Free T4 to confirm the pattern.
Low: May suggest an underactive thyroid, reduced T4-to-T3 conversion, or effects of illness or certain medicines. If results surprise you, discuss timing, supplements, and meds, then consider a repeat test with your clinician.

• TSH
• Free T4
• Total T3
• TPO antibodies

Common factors that can skew results include high-dose biotin supplements, recent thyroid medication (levothyroxine or liothyronine), antithyroid drugs, amiodarone, glucocorticoids, and heparin. Acute illness, pregnancy, estrogen therapy, severe calorie restriction, and timing differences can also shift Free T3. Aim for steady routines, and tell the lab about all medicines and supplements.

Special situations: results during pregnancy, severe illness, or soon after contrast dye may need confirmation with repeat testing or alternate methods.