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Midwest · Reverse T3 Test – rT3 Testing

Reverse T3 Test – rT3 Testing in Missouri

This page explains the reverse t3 test – rt3 testing, what it measures, and how to order it. The Reverse T3 blood test measures a form of thyroid hormone that can help clarify unusual thyroid function test results. It is often used alongside other thyroid tests to give a fuller picture of how the body is handling thyroid hormone.

Sample typeBlood and/or urine at a collection lab
ReferralIncluded — no referral from your own doctor needed

Lab requirements in Missouri

Here is what you need before ordering and completing the Reverse T3 Test – rT3 Testing in MO. Review each item and confirm the details with the collection lab.

Physician's order
Included. A physician's order is required for lab testing and is provided for you by our partner's physicians — no referral from your own doctor is needed.
Fasting
Some tests require fasting or avoiding certain foods or drinks beforehand. You will be informed when you order — confirm the details with the collection lab.
Preparation
Preparation instructions can vary depending on the laboratory and the other tests being performed at the same time. Always follow the specific instructions provided by the collection lab or…
Sample & visit
A blood and/or urine sample is collected; the visit usually takes about 10 minutes.
Identification
Bring the lab requisition form from your account. The collection lab may also ask for a government-issued photo ID.
Turnaround
1-3 business days
Availability
Our partner lab does not serve ND, RI, NY, NJ, MD or HI. Confirm availability for your location with the collection lab.

Before you go

  • Order your test before visiting a lab, then use the requisition form in your account.
  • Print the requisition form, or fax it to the lab directly from your account.
  • No scheduling is needed — visit the collection lab during its normal business hours.
  • A blood and/or urine sample is collected; the visit usually takes about 10 minutes.
  • Bring a government-issued photo ID in case the lab requests it.
  • Results are posted to your secure account within 1–3 business days.

Requirements are summarized from our partner lab's published policies. Preparation and availability can change — confirm current instructions with the collection lab before your visit.

What this test is

Reverse T3 is a biologically inactive form of thyroid hormone produced when the body converts thyroxine (T4) in an alternative pathway. This test measures the amount of reverse T3 circulating in the blood. It is not a stand-alone diagnostic test but is interpreted with other thyroid hormone measurements.

What it measures

  • Reverse T3 — reflects the amount of this inactive thyroid hormone form in the blood
  • Total T3 — often measured alongside to assess active thyroid hormone levels
  • Free T4 — helps evaluate the main thyroid hormone produced by the thyroid gland
  • TSH — indicates how the pituitary gland is responding to thyroid hormone levels

What the test involves

A healthcare professional collects a small sample of blood, usually from a vein in your arm, using a standard blood draw. The sample is then sent to a laboratory for analysis.

Why it is often ordered

A clinician may order a reverse T3 test when thyroid test results are confusing or when a nonthyroidal illness is suspected. It is typically used to help evaluate whether symptoms or abnormal thyroid tests might be related to how the body is converting thyroid hormones.

Preparation

Preparation instructions can vary depending on the laboratory and the other tests being performed at the same time. Always follow the specific instructions provided by the collection lab or your healthcare provider.

How results are reported

Results are reported as a numeric value for reverse T3, and the laboratory will provide a reference range for comparison. Reference ranges can differ between laboratories because of differences in equipment, methods, and population, so your result should be interpreted using the range from the lab that performed the test.

Before you go

  • Whether any other tests will be drawn at the same time and if fasting is required.
  • The specific reference range used by the laboratory performing the test.
  • How and when you will receive your results.

Cities

Reverse T3 Test – rT3 Testing in Missouri communities

Choose your city for local context and to order this test.

St. Louis2,092,481Reverse T3 Test – rT3 TestingKansas City1,644,497Reverse T3 Test – rT3 TestingSpringfield298,722Reverse T3 Test – rT3 TestingColumbia136,736Reverse T3 Test – rT3 TestingIndependence122,230Reverse T3 Test – rT3 TestingLee's Summit100,772Reverse T3 Test – rT3 TestingO'Fallon90,802Reverse T3 Test – rT3 TestingJoplin81,025Reverse T3 Test – rT3 TestingSt. Joseph80,099Reverse T3 Test – rT3 TestingSt. Charles70,218Reverse T3 Test – rT3 TestingBlue Springs58,265Reverse T3 Test – rT3 TestingSt. Peters57,289Reverse T3 Test – rT3 TestingFlorissant52,382Reverse T3 Test – rT3 TestingChesterfield49,675Reverse T3 Test – rT3 TestingWentzville43,213Reverse T3 Test – rT3 TestingJefferson City43,076Reverse T3 Test – rT3 TestingCape Girardeau39,415Reverse T3 Test – rT3 TestingWildwood35,384Reverse T3 Test – rT3 TestingOakville35,357Reverse T3 Test – rT3 TestingUniversity City34,953Reverse T3 Test – rT3 TestingBallwin30,998Reverse T3 Test – rT3 TestingLiberty30,129Reverse T3 Test – rT3 TestingRaytown29,893Reverse T3 Test – rT3 TestingKirkwood29,233Reverse T3 Test – rT3 TestingMehlville28,672Reverse T3 Test – rT3 TestingMaryland Heights28,141Reverse T3 Test – rT3 TestingGladstone26,825Reverse T3 Test – rT3 TestingGrandview25,931Reverse T3 Test – rT3 TestingHazelwood25,466Reverse T3 Test – rT3 TestingBelton23,832Reverse T3 Test – rT3 TestingWebster Groves23,817Reverse T3 Test – rT3 TestingNixa22,925Reverse T3 Test – rT3 TestingRaymore22,722Reverse T3 Test – rT3 TestingSedalia21,696Reverse T3 Test – rT3 TestingOzark20,874Reverse T3 Test – rT3 TestingArnold20,808Reverse T3 Test – rT3 TestingOld Jamestown20,382Reverse T3 Test – rT3 TestingRolla19,949Reverse T3 Test – rT3 TestingWarrensburg19,509Reverse T3 Test – rT3 TestingAffton18,925Reverse T3 Test – rT3 TestingFerguson18,826Reverse T3 Test – rT3 TestingConcord18,760Reverse T3 Test – rT3 TestingCreve Coeur18,648Reverse T3 Test – rT3 TestingRepublic18,313Reverse T3 Test – rT3 TestingManchester18,308Reverse T3 Test – rT3 TestingFarmington17,959Reverse T3 Test – rT3 TestingSpanish Lake17,721Reverse T3 Test – rT3 TestingKirksville17,600Reverse T3 Test – rT3 TestingHannibal17,165Reverse T3 Test – rT3 TestingClayton16,905Reverse T3 Test – rT3 TestingLake St. Louis16,665Reverse T3 Test – rT3 TestingPoplar Bluff16,318Reverse T3 Test – rT3 TestingLemay16,312Reverse T3 Test – rT3 TestingSikeston16,054Reverse T3 Test – rT3 TestingOverland15,908Reverse T3 Test – rT3 TestingFort Leonard Wood15,629Reverse T3 Test – rT3 TestingGrain Valley15,435Reverse T3 Test – rT3 TestingCarthage15,395Reverse T3 Test – rT3 TestingJackson15,272Reverse T3 Test – rT3 TestingLebanon14,880Reverse T3 Test – rT3 Testing