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How long does Armour Thyroid stay in your system?

Medically reviewed by Sally Chao, MD. Last updated on Sep 1, 2021.

Official answer


Armour Thyroid contains two different thyroid hormones derived from pigs, T3 and T4, and T4 will remain in your system longer than T3.

  • Most people will clear T3 from the body in around 4 days.
  • T4 is eliminated in around 4 to 5 weeks for people with a normally functioning thyroid. Those with an overactive thyroid (hyperthyroidism) will clear T4 quicker (2 to 3 weeks), but it may take around 6 to 7 weeks for people with an underactive thyroid (hypothyroidism) to eliminate T4.

However, these are estimates based on the half-lives of these compounds. The processes involved in absorbing, utilizing and eliminating this combination of thyroid hormones is complex and sensitive, and can be altered by factors including your weight, age, thyroid function, underlying diseases and other medications, such as:

  • Birth control pills
  • Blood thinners
  • Diabetes medications
  • Aspirin
  • Steroids
  • Iodine-containing medications

The time it takes to eliminate these hormones can vary depending on these and other factors. For example, thyroid hormones are eliminated more slowly in people with hypothyroidism compared to those with normal thyroid function.

Armour Thyroid also contains other ingredients. Other ingredients include:

  • Calcium stearate
  • Dextrose
  • Microcrystalline cellulose
  • Sodium starch glycolate
  • Opadry white (a film coating)

Armour Thyroid is mainly excreted through urine.

People who are prescribed Armour Thyroid or the FDA-approved synthetic thyroid hormones, such as levothyroxine, which are absorbed similarly, generally achieve steady levels of the hormone within 6 weeks of starting treatment.

  1. Allergan. Armour® Thyroid (thyroid tablets, USP). June 2018. Available at: [Accessed August 25, 2021].
  2. Thyroid, desiccated. October 2020. Available at: [Accessed August 25, 2021].
  3. U.S. Food and Drug Administration (FDA). CYTOMEL®. Available at: [Accessed August 19, 2021].
  4. American Thyroid Association (ATA). Hypothyroidism: A Booklet for Patients and Their Families. 2019. Available at: [Accessed August 19, 2021].
  5. Colucci P, Yue CS, Ducharme M, Benvenga S. A Review of the Pharmacokinetics of Levothyroxine for the Treatment of Hypothyroidism. Eur Endocrinol. 2013;9(1):40-47. doi: 10.17925/EE.2013.09.01.40.
  6. Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement. Thyroid. 2014;24(12):1670-1751. doi: 10.1089/thy.2014.0028.
  7. Armour Thyroid. May 3, 2021. Available at: [Accessed August 25, 2021].

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