Order Reverse T3 Blood Test from JustLabs for $28 ($46 all-in for a single-test order: $28 + one $18 lab & physician order fee per order). Price includes lab processing at Quest Diagnostics. No insurance required.
Reverse T3 (rT3) is an inactive form of thyroid hormone produced when the body diverts T4 conversion away from active T3. Elevated levels may indicate stress, illness, or thyroid conversion problems.
Reverse T3 (rT3) is a metabolically inactive form of thyroid hormone. Your body normally converts T4 (the storage hormone) into T3 (the active hormone), but under certain conditions, it instead converts T4 into rT3, which blocks T3 receptors without activating them.
This "thyroid shunting" is a protective mechanism during illness, stress, or calorie restriction—slowing metabolism to conserve energy. However, chronically elevated rT3 can cause hypothyroid symptoms despite normal TSH and T4 levels.
Reverse T3 testing is controversial in mainstream medicine but valued in functional medicine for explaining persistent hypothyroid symptoms with normal conventional labs. The ratio of Free T3 to Reverse T3 may be more informative than rT3 alone.
Price
$28
All-in
$46
incl. $18 lab & physician fee
Results
3-5 business days
Fasting
Not Required
What's Measured
What This Test Measures
This test measures the concentration of Reverse T3 in your blood, reported in ng/dL. It's often interpreted alongside Free T3 to calculate the Free T3:Reverse T3 ratio.
Who Should Consider This Test
People with hypothyroid symptoms despite normal TSH, those with chronic illness or stress, anyone investigating "low T3 syndrome," people on T4-only thyroid medication with persistent symptoms, and those evaluating thyroid conversion issues.
Health Insights
Conditions Screened
Related Symptoms
When to Get Tested
No fasting required. Best tested alongside Free T3 and Free T4 for complete interpretation. Avoid testing during acute illness unless evaluating sick euthyroid syndrome.
No fasting needed. How to prepare for your blood test →
Understanding Your Results
Normal Reverse T3: 9-27 ng/dL. More important is the Free T3:Reverse T3 ratio. Ratios above 20 (when Free T3 is in pg/mL and rT3 in ng/dL) are generally considered optimal. Lower ratios suggest T4-to-rT3 shunting.
What to Expect
After placing your order, we send it straight to Quest Diagnostics — there is no consent form to sign and no partner email to wait for. Your requisition is usually ready to download from your dashboard within about an hour, and you can book your blood draw at any Quest Diagnostics location.
The blood draw typically takes just a few minutes. Results are usually available within 3-5 business days and will appear in your secure JustLabs dashboard.
Our results include reference ranges and easy-to-understand indicators showing whether your values are within normal limits.
How much does the Reverse T3 test cost?
The Reverse T3 test costs $28 at JustLabs — $46 all-in, since the $18 lab & physician order fee is charged once per order, however many tests you add. The price is fixed before your blood draw; no insurance or doctor visit needed.
| Option | Price | Order all-in | Notes |
|---|---|---|---|
| Reverse T3 at JustLabsDrawn at Quest Diagnostics | $28 | $46 | Includes the one $18 fee, charged once per order |
Paying with an HSA or FSA? See which lab tests qualify
Frequently Asked Questions
Hospital cash price: $120–$180
$28
+ $18 order fee · $46 all-inOne $18 fee per order covers your Quest blood draw and the independent physician order, however many tests you add.
- Results in 3-5 business days
- No fasting required
- Physician order included
No insurance needed · HSA/FSA eligible
- Physician-ordered
- CLIA-certified Quest lab
- Drawn at Quest Diagnostics
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