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Reverse T3
Access Labcorp Draw · Access Medical Labs2 test optionsFrom $47.19
Reverse T3
Access Labcorp Draw · Access Medical LabsCatalog information reviewed: August 24, 2026 by the Sunridge Medical clinical team.
What this laboratory test evaluates
DetailsReverse T3 (rT3) is an inactive form of the thyroid hormone T3 that is produced under stress or illness when the body converts T4 into rT3 instead of active T3. It is used to assess thyroid hormone conversion efficiency and may help identify non-thyroidal illness or functional hypothyroidism.
What type of sample is required for this test?Serum
Test ResourcesFor more information, please consult your healthcare provider.
Additional test information
Reverse T3 (rT3) is an inactive form of the thyroid hormone T3 that is produced under stress or illness when the body converts T4 into rT3 instead of active T3. It is used to assess thyroid hormone conversion efficiency and may help identify non-thyroidal illness or functional hypothyroidism.
Collection and processing
- Sample type: Serum
- Fasting: No
- Estimated laboratory processing: Results should arrive 4 – 6 business days after the lab receives samples.
How Sunridge uses laboratory information
Sunridge considers the medical question, symptoms, history, medications, prior results, and whether the finding could change care before recommending testing. A laboratory result is not interpreted in isolation and does not establish a diagnosis by itself.
Before requesting this test
Availability, collection requirements, eligibility, and processing estimates can change. Sunridge reviews each request and, when appropriate, creates the order through Fullscript. Follow the current instructions supplied with the approved order.
Common questions about this laboratory test
- What sample does this test require?
- The listed sample type is Serum. Confirm current collection instructions in the approved order.
- Does this test require fasting?
- The current catalog record lists fasting as: No. Follow the instructions supplied with the approved order.
- How long does laboratory processing usually take?
- Results should arrive 4 – 6 business days after the lab receives samples.. Timing can change after collection or if a laboratory requires additional review.
About this test
DetailsReverse T3 (rT3) is an inactive form of the thyroid hormone T3 that is produced under stress or illness when the body converts T4 into rT3 instead of active T3. It is used to assess thyroid hormone conversion efficiency and may help identify non-thyroidal illness or functional hypothyroidism.
What type of sample is required for this test?Serum
Test ResourcesFor more information, please consult your healthcare provider.
Additional details
Reverse T3 (rT3) is an inactive form of the thyroid hormone T3 that is produced under stress or illness when the body converts T4 into rT3 instead of active T3. It is used to assess thyroid hormone conversion efficiency and may help identify non-thyroidal illness or functional hypothyroidism.
Highlighted health areas
- Hormones
- Thyroid
Biomarkers and report focus
The exact analytes and report format can change. Confirm the current contents in the Fullscript order before payment.
- Reverse T3