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Midwest · Reverse T3 Test – rT3 Testing

Reverse T3 Test – rT3 Testing in Illinois

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 Illinois

Here is what you need before ordering and completing the Reverse T3 Test – rT3 Testing in IL. 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 Illinois communities

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

Chicago8,595,181Reverse T3 Test – rT3 TestingRockford289,763Reverse T3 Test – rT3 TestingRound Lake Beach287,012Reverse T3 Test – rT3 TestingPeoria255,718Reverse T3 Test – rT3 TestingAurora183,447Reverse T3 Test – rT3 TestingSpringfield162,588Reverse T3 Test – rT3 TestingChampaign153,278Reverse T3 Test – rT3 TestingJoliet150,323Reverse T3 Test – rT3 TestingNaperville149,013Reverse T3 Test – rT3 TestingBloomington134,357Reverse T3 Test – rT3 TestingElgin114,156Reverse T3 Test – rT3 TestingWaukegan89,751Reverse T3 Test – rT3 TestingDecatur88,002Reverse T3 Test – rT3 TestingCicero84,905Reverse T3 Test – rT3 TestingAlton83,705Reverse T3 Test – rT3 TestingKankakee82,095Reverse T3 Test – rT3 TestingEvanston78,454Reverse T3 Test – rT3 TestingSchaumburg78,053Reverse T3 Test – rT3 TestingArlington Heights77,283Reverse T3 Test – rT3 TestingBolingbrook73,807Reverse T3 Test – rT3 TestingPalatine67,754Reverse T3 Test – rT3 TestingSkokie67,444Reverse T3 Test – rT3 TestingDeKalb66,624Reverse T3 Test – rT3 TestingCarbondale66,482Reverse T3 Test – rT3 TestingDes Plaines60,413Reverse T3 Test – rT3 TestingOrland Park58,622Reverse T3 Test – rT3 TestingOak Lawn58,032Reverse T3 Test – rT3 TestingBerwyn56,960Reverse T3 Test – rT3 TestingMount Prospect56,510Reverse T3 Test – rT3 TestingTinley Park55,988Reverse T3 Test – rT3 TestingOak Park54,100Reverse T3 Test – rT3 TestingWheaton53,762Reverse T3 Test – rT3 TestingNormal53,446Reverse T3 Test – rT3 TestingHoffman Estates52,153Reverse T3 Test – rT3 TestingDowners Grove50,209Reverse T3 Test – rT3 TestingGlenview48,150Reverse T3 Test – rT3 TestingElmhurst45,661Reverse T3 Test – rT3 TestingLombard44,311Reverse T3 Test – rT3 TestingPlainfield44,296Reverse T3 Test – rT3 TestingBuffalo Grove43,062Reverse T3 Test – rT3 TestingMoline42,660Reverse T3 Test – rT3 TestingBelleville42,463Reverse T3 Test – rT3 TestingBartlett41,126Reverse T3 Test – rT3 TestingRomeoville40,099Reverse T3 Test – rT3 TestingCrystal Lake40,082Reverse T3 Test – rT3 TestingCarol Stream39,895Reverse T3 Test – rT3 TestingStreamwood39,736Reverse T3 Test – rT3 TestingQuincy39,687Reverse T3 Test – rT3 TestingPark Ridge39,562Reverse T3 Test – rT3 TestingUrbana39,189Reverse T3 Test – rT3 TestingWheeling39,104Reverse T3 Test – rT3 TestingCarpentersville37,940Reverse T3 Test – rT3 TestingHanover Park37,545Reverse T3 Test – rT3 TestingRock Island37,519Reverse T3 Test – rT3 TestingCalumet City36,065Reverse T3 Test – rT3 TestingAddison35,999Reverse T3 Test – rT3 TestingNorthbrook35,108Reverse T3 Test – rT3 TestingOswego34,324Reverse T3 Test – rT3 TestingWoodridge34,161Reverse T3 Test – rT3 TestingGlendale Heights33,443Reverse T3 Test – rT3 Testing