Free T3 (FT3) is the unbound, biologically active form of triiodothyronine (T3), the thyroid hormone that directly regulates metabolism at the cellular level. Measuring FT3 indicates how much hormone is actually available to enter cells and exert physiological effects. Only about 0.3% of total T3 is free; the remainder is bound to proteins and biologically inactive. Therefore, FT3 measurement can reflect thyroid hormone activity, peripheral T4-to-T3 conversion efficiency, and tissue-level thyroid hormone effects.

The RayBio^® Free T3 Enzyme Immunoassay (EIA) Kit is a competitive immunoassay that quantifies T3 in serum or plasma from human, mouse, rat, porcine, feline, canine, equine, and sheep samples, as well as urine samples within 2.5 hours. Absorbance is measured at 450 nm, and concentrations are interpolated from a ready-to-use T3 standard curve. The assay demonstrates a sensitivity of 0.002 ng/dL and has been validated for linearity, stability, precision, and spike-recovery performance. Each kit provides sufficient reagents to perform up to 96 assays, including standard curve and unknown samples.

• Various species
• High sensitivity
• Rapid detection within 2.5 hours
• Good characteristics in terms of linearity, stability, precision, and spiking & recovery

• Pre-Coated 96-well Strip Microplate
• Assay Diluent
• Lyophilized Standard
• Positive Control
• Capture Antibody
• HRP-conjugated Secondary Antibody
• Wash Buffer
• TMB One-Step Substrate Reagent
• Stop Solution

• Microplate reader capable of measuring absorbance at 450 nm
• Precision pipettes to deliver 2 μL to 1 mL volumes
• Adjustable 1-25 mL pipettes for reagent preparation
• 100 mL and 1-liter graduated cylinders
• Distilled or deionized water
• Tubes to prepare standard or sample dilutions
• Orbital shaker
• Software which can perform four-parameter logistic regression models

1. Prepare all reagents, samples and standards as instructed.
2. Add 50 µL standards or samples to appropriate well. Incubate for 10 minutes at room temperature.
3. Add 50 µL Capture Antibody to appropriate well. Incubate 1 hour at room temperature. And wash 5 times.
4. Add 100 µL prepared HRP-Secondary Antibody solution. Incubate 1 hour at room temperature. And wash 5 times.
5. Add 100 µL TMB One-Step Substrate Reagent to each well. Incubate 5-20 minutes at room temperature.
6. Add 50 µL Stop Solution to each well. Read at 450 nm immediately.