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New England · Reverse T3 Test – rT3 Testing

Reverse T3 Test – rT3 Testing in Massachusetts

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 Massachusetts

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

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

Boston4,208,580Reverse T3 Test – rT3 TestingSpringfield620,494Reverse T3 Test – rT3 TestingWorcester573,573Reverse T3 Test – rT3 TestingNew Bedford158,353Reverse T3 Test – rT3 TestingLeominster118,190Reverse T3 Test – rT3 TestingCambridge116,892Reverse T3 Test – rT3 TestingLowell114,804Reverse T3 Test – rT3 TestingBrockton104,216Reverse T3 Test – rT3 TestingQuincy100,544Reverse T3 Test – rT3 TestingLynn100,233Reverse T3 Test – rT3 TestingFall River93,339Reverse T3 Test – rT3 TestingNewton88,647Reverse T3 Test – rT3 TestingLawrence87,798Reverse T3 Test – rT3 TestingSomerville80,608Reverse T3 Test – rT3 TestingFramingham72,089Reverse T3 Test – rT3 TestingHaverhill67,093Reverse T3 Test – rT3 TestingMalden65,602Reverse T3 Test – rT3 TestingWaltham64,655Reverse T3 Test – rT3 TestingRevere60,720Reverse T3 Test – rT3 TestingMedford60,708Reverse T3 Test – rT3 TestingTaunton59,076Reverse T3 Test – rT3 TestingChicopee55,636Reverse T3 Test – rT3 TestingPeabody54,200Reverse T3 Test – rT3 TestingMethuen Town52,536Reverse T3 Test – rT3 TestingEverett48,368Reverse T3 Test – rT3 TestingAttleboro46,146Reverse T3 Test – rT3 TestingSalem44,452Reverse T3 Test – rT3 TestingPittsfield43,890Reverse T3 Test – rT3 TestingBeverly42,448Reverse T3 Test – rT3 TestingFitchburg41,796Reverse T3 Test – rT3 TestingMarlborough41,505Reverse T3 Test – rT3 TestingWoburn40,967Reverse T3 Test – rT3 TestingWestfield40,922Reverse T3 Test – rT3 TestingChelsea40,025Reverse T3 Test – rT3 TestingHolyoke38,480Reverse T3 Test – rT3 TestingWatertown Town35,171Reverse T3 Test – rT3 TestingGloucester29,814Reverse T3 Test – rT3 TestingMelrose29,567Reverse T3 Test – rT3 TestingNorthampton29,379Reverse T3 Test – rT3 TestingGardner21,183Reverse T3 Test – rT3 TestingNewburyport18,282Reverse T3 Test – rT3 TestingNorth Adams13,024Reverse T3 Test – rT3 TestingSouth Yarmouth11,696Reverse T3 Test – rT3 TestingMiddleborough Center7,790Reverse T3 Test – rT3 TestingMansfield Center7,689Reverse T3 Test – rT3 TestingWhitinsville7,329Reverse T3 Test – rT3 TestingWest Concord7,003Reverse T3 Test – rT3 TestingCochituate6,966Reverse T3 Test – rT3 TestingEast Falmouth6,739Reverse T3 Test – rT3 TestingPinehurst6,653Reverse T3 Test – rT3 TestingWest Yarmouth6,124Reverse T3 Test – rT3 TestingYarmouth Port5,872Reverse T3 Test – rT3 TestingBliss Corner5,529Reverse T3 Test – rT3 TestingNorth Scituate5,519Reverse T3 Test – rT3 TestingEast Harwich5,519Reverse T3 Test – rT3 TestingRaynham Center5,072Reverse T3 Test – rT3 TestingSmith Mills4,846Reverse T3 Test – rT3 TestingNorth Westport4,835Reverse T3 Test – rT3 TestingThe Pinehills4,724Reverse T3 Test – rT3 TestingMillis-Clicquot4,653Reverse T3 Test – rT3 Testing