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All biomarkers
Hormones

Free T3 (free triiodothyronine)

Measured in pg/mL · LOINC 3051-0

Reference ranges

Optimal
3.24.4 pg/mL
functional-medicine target
Standard
2.34.2 pg/mL
lab reference range

Optimal ranges are tighter than standard lab ranges and reflect functional-medicine targets, not the populations they were derived from. Reference bands depend on sex, age, and circumstance — Juno's lab analysis layers your profile context onto the printed range when you paste a value.

Peptide relevance

Biologically active thyroid hormone — symptoms correlate with T3 more than T4. Low T3 with normal T4 can indicate poor T4→T3 conversion (selenium / zinc deficiency, chronic stress, low-calorie dieting, illness). Common in users doing aggressive cuts or fasting. Tirzepatide / Semaglutide may slightly lower T3 during rapid weight loss (adaptive thermogenesis). No direct peptide effects from the standard stack peptides documented. Reverse T3 (rT3) is the inactive isomer — order alongside if poor conversion is suspected.

Have a recent Free T3 (free triiodothyronine) value?

Paste it on the lab analysis page. Juno reads your active stack + (if shared) your medications and conditions, and surfaces plausible contributors with citations. Doesn't diagnose.

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