ThyroidPrices verified 2026-03-23
Reverse T3 Serum/Plasma
Reverse T3 (rT3) is an inactive isomer of T3, formed from T4. During periods of stress, illness, or caloric restriction, the body may preferentially convert T4 to rT3 instead of active T3, conserving energy. Elevated rT3 can indicate non-thyroidal illness ('euthyroid sick syndrome') or impaired T4-to-T3 conversion. The ratio of Free T3 to rT3 (e.g., FT3(pg/mL)/rT3(ng/dL) > 0.2) is sometimes used to assess conversion efficiency.
Cost Recon
Self-Pay Price Comparison
| Provider | Price | vs. Highest | Order |
|---|---|---|---|
Quest QuestHealth self-pay | Not Available | N/A | Check Provider Site · Quest |
LabCorp Labcorp OnDemand | Not Available | N/A | Check Provider Site · LabCorp |
GoodLabs Discount lab network | $32.00Best value | Best price | Order · GoodLabs |
About GoodLabs: About GoodLabs: GoodLabs offers the same Quest and LabCorp tests at discounted self-pay rates. Their prices reflect direct negotiated rates; not retail list prices.
Recon Snapshot
What This Test Measures
Key analytes included in this test (see your lab’s order for the full finalized list).
Reverse T3
Clinical Notes
Reverse T3 is produced by deiodination of T4 to a biologically inactive form. Elevated rT3 may reflect impaired T4-to-T3 conversion in illness, stress, or selenium deficiency.