A Reverse T3 (rT3) test measures the level of reverse triiodothyronine, an inactive form of thyroid hormone. Unlike active T3, reverse T3 does not stimulate metabolism and may actually block T3 receptors.
What This Test Measures
Reverse T3 (rT3):
When your body converts T4 to T3, a portion is converted to reverse T3 instead. Reverse T3 is metabolically inactive and acts as a “brake” on thyroid function. The ratio between active T3 and reverse T3 affects how thyroid hormone functions in your body.
Reference Ranges
Normal Reverse T3: 9.2-24.1 ng/dL (ranges vary by laboratory)
More important than absolute value is the ratio of Free T3 to Reverse T3.
Who Should Consider This Test
• Those with thyroid symptoms despite normal TSH and T4:
– Persistent fatigue
– Weight issues
– Cold intolerance
– Brain fog
• People under chronic stress or recovering from illness
• Those with chronic fatigue syndrome or fibromyalgia
• Anyone with suspected thyroid hormone conversion issues
• Patients on thyroid medication who still feel unwell
• Those interested in comprehensive thyroid evaluation
When Reverse T3 Increases
Your body produces more reverse T3 (and less active T3) during:
• Chronic illness or acute illness
• Severe calorie restriction or fasting
• High stress (elevated cortisol)
• Certain medications
• Inflammation
• Aging
This is sometimes called “Low T3 Syndrome” or “Euthyroid Sick Syndrome” – the body conserves energy by reducing metabolic rate.
How It Works
1. Order your test online – no doctor visit required
2. Visit any Quest Diagnostics location nationwide
3. Simple blood draw takes approximately 5 minutes
4. Results delivered to your secure portal within 1-2 business days
Preparation
No fasting required.
Related Tests to Consider
• Free T3 – Active thyroid hormone (calculate ratio with rT3)
• Free T4 – Main thyroid output
• TSH – Primary thyroid screening
• Cortisol – Stress hormone affecting T3 conversion
• Comprehensive Thyroid Panel – Complete evaluation
Why Choose Wittmer Rejuvenation Clinic
At $70, our Reverse T3 test is competitively priced. We partner with Quest Diagnostics for reliable, CLIA-certified laboratory testing with convenient locations across all 50 states.
Reviews
There are no reviews yet.