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How long does Tirosint stay in your system?

Medically reviewed by Carmen Fookes, BPharm. Last updated on Sep 16, 2021.

Official answer


Tirosint stays in your system a long time, taking approximately 45 days (6 or 7 weeks) for your body to completely clear it, although its effects do not take that long to wear off. This estimate is based on the half-life of levothyroxine (or T4) which is contained in Tirosint. The half-life of levothyroxine (Tirosint) is about 6 to 7 days and experts agree that it takes up to 5 half-lives for a drug without active metabolites to be completely removed from the body. A drug’s half-life is the time it takes for 50% of that drug to be removed from the body. However, levothyroxine (T4) is metabolized to liothyronine (T3) which has a half-life of ≤ 2 days, so this needs to be considered as well. The final calculation estimates it takes 45 days for Tirosint (T4) and its metabolite (T3) to leave the body.

This calculation is an estimate only because other, individual factors must be taken into account. For example, how a person’s thyroid is functioning. 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.

In addition, the processes involved in absorbing, utilizing, and eliminating thyroid hormones is complex and sensitive and can be altered by factors including a person’s weight, age, underlying diseases, and other medications, such as:

  • Birth control pills
  • Blood thinners
  • Diabetes medications
  • Aspirin
  • Steroids
  • Iodine-containing medications.
  • Tirosint (levothyroxine) Updated 09/2020[CF1] IBSA Pharma Inc.

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