Reverse T3 levels: what's normal, high and low
An inactive form of T3 that the body produces during stress, illness, or low-calorie states.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
The short answer
Reverse T3 is measured with a standard blood draw; no fasting is needed. A typical reference range is 8.00 – 25.0 ng/dL. At TestWell it's $35.99 all-in as Reverse T3, results in 4–7 business days, drawn at Quest or Labcorp. An out-of-range result is a prompt to look closer, not a diagnosis.
- Units
- ng/dL
- Sample
- Blood draw
- Fasting
- Not required
- Results
- 4–7 business days
- Price
- $35.99
- Labs
- Quest or Labcorp · BioReference in NY/NJ
Reverse T3 Reference Range
These are the typical adult reference ranges used by major US labs. Your report will include the specific range used by the lab that processed your sample.
| Population | Range |
|---|---|
| age 18+ | 8.00 – 25.0 ng/dL |
Reference ranges are educational. Always interpret your result with the specific range printed on your lab report and discuss anything outside the range with a clinician.
Have a result in hand? analyze it with your AI assistant using these reviewed ranges, or run it through our explainer. Tools: look up another marker's range · convert lab units
What your Reverse T3 result may mean
Can reflect physiological stress, illness, severe dieting, or certain medications.
What a high Reverse T3 means: causes, symptoms, next steps ↓Educational only — not a diagnosis. Many factors can influence a single result. Discuss anything that concerns you with a healthcare provider.
What does a high Reverse T3 mean?
Reverse T3 is an inactive form of thyroid hormone the body makes more of during illness, fasting, severe calorie restriction, surgery, and with some medications (amiodarone, glucocorticoids, beta-blockers). A high level is a marker of that physiological stress — not, by mainstream guidelines, a thyroid disease to treat. It is interpreted alongside TSH, Free T4 and Free T3.
Common causes of a high Reverse T3
- Acute or chronic illness, hospitalization, sepsis
- Fasting, very low-calorie dieting, eating disorders
- Medications: amiodarone, propranolol, glucocorticoids, iodinated contrast
- Levothyroxine dose changes (transient)
- Older age (mild)
Ordered from most to least common.
Symptoms that can go with it
- None from reverse T3 itself; fatigue and cold intolerance are usually from the underlying illness or calorie deficit
What clinicians usually check next
- TSH, Free T4 and Free T3 — the actionable thyroid tests
- Review recent illness, dieting and medications
- Retest when well and eating normally; most values normalize
Follow-up tests at TestWell: TSH (Thyroid Stimulating Hormone) ($26.99), TSH + Free T4 ($27.99), Free T3 (Triiodothyronine) ($30.99), Free T4 (Thyroxine) ($23.99), T3 Uptake ($22.99), T3, Total (Triiodothyronine) ($24.99).
Should high reverse T3 be treated with T3 medication?
Major endocrine guidelines do not recommend it. Reverse T3 rises as a normal response to illness and calorie deficit; addressing those, not adding hormone, is the evidence-based path.
Educational only — not a diagnosis. A single result outside the range is a prompt to look closer with a clinician.
How do you get a Reverse T3 test?
Order online, a licensed physician reviews the requisition, and you walk into a nearby lab for the draw. Reverse T3 is available on its own or inside these panels — panels cost less per marker when you want the fuller picture.
| Option | Includes | Price |
|---|---|---|
| Reverse T3 | This marker only | $35.99 |
| Complete Thyroid Panel | 4 tests | $109.99 |
| Advanced Thyroid Panel | 7 tests | $129.99 |
| Female HRT Starting Panel | 20 tests | $249.99 |
| Men's Health Advanced Panel | 22 tests | $299.99 |
Quest vs. Labcorp for Reverse T3: which lab should you pick?
Both are CLIA-certified national labs and the result is clinically equivalent, so pick whichever location is closer. Your report will print that lab's own reference range, which can differ slightly from the table above.
| Lab | Available | Price |
|---|---|---|
| Quest Diagnostics | Yes | $35.99 |
| Labcorp | Yes | $35.99 |
| BioReference (NY & NJ) | Yes | $39.99 |
Need help choosing a location? Use the lab finder to see draw sites near your ZIP.
Related Thyroid biomarkers
Markers commonly tested alongside Reverse T3.
Frequently asked
What does a high Reverse T3 mean?
Reverse T3 is an inactive form of thyroid hormone the body makes more of during illness, fasting, severe calorie restriction, surgery, and with some medications (amiodarone, glucocorticoids, beta-blockers). A high level is a marker of that physiological stress — not, by mainstream guidelines, a thyroid disease to treat. It is interpreted alongside TSH, Free T4 and Free T3.
Should high reverse T3 be treated with T3 medication?
Major endocrine guidelines do not recommend it. Reverse T3 rises as a normal response to illness and calorie deficit; addressing those, not adding hormone, is the evidence-based path.
Do I need a doctor's order to test my reverse t3?
No. TestWell's licensed physician network reviews and approves your order — usually within minutes. You can place an order online without an in-person visit or a referral from your own doctor.
How long does it take to get Reverse T3 results?
Most Reverse T3 results are available in 1–3 business days after your specimen arrives at the lab. You'll get an email the moment your results are ready, with everything viewable in your TestWell portal.
How much does a Reverse T3 test cost?
Our Reverse T3 starts at $35.99. That's the all-in price — no copays, no insurance hoops, no surprise bills. HSA and FSA cards are accepted.
Do I need to fast before my Reverse T3 test?
Fasting is not required for the Reverse T3 test. You can have your blood drawn any time of day.
Which lab will process my Reverse T3 test?
Your test will be processed by Quest Diagnostics, Labcorp, or BioReference depending on which is closest to you and which lab carries the test. All three are CLIA-certified and trusted by hospitals nationwide. You'll choose your lab during checkout from 4,000+ locations.
Ready to test your reverse t3?
Order in two minutes, get physician-approved, and visit a lab the same day. Starts at $35.99.