What is Levothyroxine used for?

Levothyroxine is indicated for: Hypothyroidism, Iatrogenic hypothyroidism (post-I131 or surgery), induction of moult, lifetime management, may induce molt, Post-thyroidectomy hormone replacement, thyroid supplementation.

Which species have cited Levothyroxine dosing data?

Levothyroxine dosing in the ExoticRx formulary covers 16 species: African Grey Parrot, Amazon Parrot, Cat (Domestic), Crested Gecko, Degu, Dog (Domestic), Domestic Pigeon, Dwarf Hamster, Green-cheeked Conure, Guinea Pig, Leopard Gecko, Lovebird, Pet Rat, Russian Tortoise, Sulcata Tortoise, Umbrella Cockatoo.

Is Levothyroxine a controlled substance?

Levothyroxine is not federally scheduled in the US. Controlled-drug status differs by country — verify your local rules.

How does Levothyroxine work?

Synthetic T4 (thyroxine) that is converted to active T3 in peripheral tissues. Restores normal metabolic rate, thermogenesis, and organ function.

Levothyroxine

US brand names:Soloxine, Thyro-Tabs

Calculate dosage

Sourced from published veterinary references. Awaiting credentialed clinical reviewer — our editorial process.

Levothyroxine is dosed at 0.02 mg/kg PO q48h in crested geckos, per Hadfield CA, Clayton LA, Clancy MM. Proliferative thyroid lesions in three diplodactylid geckos: Nephrurus amyae, Nephrurus levis, and Oedura marmorata. J Zoo Wildl Med. 2012;43:131-140. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.260 doi:10.1638/2011-0106.1 — Carpenter's Exotic Animal Formulary 6th ed, Table 4.8 (Hormones and Steroids Used in Reptiles). The copy held is an ebook conversion with no printed page numbers, so the table — not the page — is the citable location. — SOURCE EDITION: Carpenter's Exotic Animal Formulary — ISBN 9780323833929, https://openlibrary.org/isbn/9780323833929; Clinical Guide to Fish Medicine — ISBN 9781119259558, https://openlibrary.org/isbn/9781119259558. Verify against current literature before clinical use.

Drug Class

Endocrine

Side effects & warnings

Dose based on body weight, adjusted by monitoring serum T4 levels (4-6 hour post-pill sample). Give on empty stomach. Monitor for signs of thyrotoxicosis (tachycardia, panting, anxiety). Dogs primarily.

Backed by 15 published sources

· 122. Meredith A. BSAVA Small Animal Formulary: Part B: Exotic Pets, British Small Animal Veterinary Association, Quedgeley, Gloucester, UK; 2015. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.801 — Carpenter's Exotic Animal Formulary 6th ed, Table 9.7 (Miscellaneous Agents Used in Rodents). The copy held is an ebook conversion with no printed page numbers, so the table — not the page — is the citable location. — SOURCE EDITION: BSAVA Small Animal Formulary, Part B — Exotic Pets — ISBN 9781910443712, https://openlibrary.org/isbn/9781910443712; Carpenter's Exotic Animal Formulary — ISBN 9780323833929, https://openlibrary.org/isbn/9780323833929
· 159. Formulary. In: Chitty J, Lierz M, Chitty J, Lierz M, eds. BSAVA Manual of Raptors, Pigeons and Passerine Birds; British Small Animal Veterinary Association, Gloucester, UK; 2008:384-390. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.463 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.7 (Hormones and Steroids Used in Birds). The copy held is an ebook conversion with no printed page numbers, so the table — not the page — is the citable location. — SOURCE EDITION: BSAVA Manual of Raptors, Pigeons and Passerine Birds (Chitty J, Lierz M, eds., 2008) — Canine and Feline — ISBN 9781905319046, ; Carpenter's Exotic Animal Formulary — ISBN 9780323833929,

Sample dosing (2 of 16 cited rules)

A dog/cat sample is shown here. Cited dosing for all 16 species — reptiles, birds, pocket pets, livestock, and equine — is free on the per-species pages above. Pro adds the weight-based calculator for every species.

Species	Route	Dose	Frequency	Evidence	Source
Dog (Domestic)	PO	0.02 mg/kg	q12h	Strong	Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.777 (2026-08-01). — Plumb's 10th ed (held) printed p.749, Levothyroxine monograph spanning p.749-751; page located 2026-08-05 from the book's own running heads, verified to name the drug in its body text. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207
Cat (Domestic)	PO	0.05–0.1 mg per cat	q24h	Moderate	Scott-Moncrieff JC. Chapter 3: Hypothyroidism. In: Canine and Feline Endocrinology. 4th ed. Elsevier Saunders; 2015.; Peterson ME, Carothers MA, Gamble DA, Rishniw M. Spontaneous primary hypothyroidism in 7 adult cats. J Vet Intern Med. 2018;32(6):1864-1873. doi:10.1111/jvim.15417 — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.778 (2026-08-01). — Plumb's 10th ed (held) printed p.749, Levothyroxine monograph spanning p.749-751; page located 2026-08-05 from the book's own running heads, verified to name the drug in its body text. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207,

· 351. Norton TM, Jacobson ER, Caligiuri R, et al. Medical management of a Galapagos tortoise (Geochelone elephantopus) with hypothyroidism. J Zoo Wildl Med. 1989;20:212-216. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.261 — Carpenter's Exotic Animal Formulary 6th ed, Table 4.8 (Hormones and Steroids Used in Reptiles). The copy held is an ebook conversion with no printed page numbers, so the table — not the page — is the citable location. — SOURCE EDITION: Carpenter's Exotic Animal Formulary — ISBN 9780323833929, https://openlibrary.org/isbn/9780323833929

· 391. Hawkins MG, Barron H, Speer BL, et al. Birds. In: Carpenter JW, eds. Exotic Animal Formulary, 4th ed., Elsevier Saunders, St. Louis, MO; 2013:183-437. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.463 — SOURCE EDITION: Carpenter's Exotic Animal Formulary — ISBN 9780323833929, https://openlibrary.org/isbn/9780323833929; Current Therapy in Avian Medicine and Surgery — ISBN 9781455746712, https://openlibrary.org/isbn/9781455746712

· 43. Bailey TA, Apo MM. Pharmaceutics commonly used in avian medicine. In: Samour J, eds. Avian Medicine, 3rd ed., Mosby Elsevier, Edinburgh, Scotland; 2016:637-678. | 159. Formulary. In: Chitty J, Lierz M, eds. BSAVA Manual of Raptors, Pigeons and Passerine Birds; British Small Animal Veterinary Association, Gloucester, UK; 2008:384-390. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.463 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.7 (Hormones and Steroids Used in Birds). The copy held is an ebook conversion with no printed page numbers, so the table — not the page — is the citable location. — SOURCE EDITION: BSAVA Small Animal Formulary, Part A — Canine and Feline — ISBN 9781910443705, https://openlibrary.org/isbn/9781910443705; Carpenter's Exotic Animal Formulary — ISBN 9780323833929, https://openlibrary.org/isbn/9780323833929; Avian Medicine (Samour) — ISBN 9780723438328, https://openlibrary.org/isbn/9780723438328

· 43. Bailey TA, Apo MM. Pharmaceutics commonly used in avian medicine. In: Samour J, eds. Avian Medicine, 3rd ed., Mosby Elsevier, Edinburgh, Scotland; 2016:637-678. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.463 doi:10.1016/b978-0-7234-3832-8.00023-7 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.7 (Hormones and Steroids Used in Birds). The copy held is an ebook conversion with no printed page numbers, so the table — not the page — is the citable location. — SOURCE EDITION: Carpenter's Exotic Animal Formulary — ISBN 9780323833929, https://openlibrary.org/isbn/9780323833929; Avian Medicine (Samour) — ISBN 9780723438328, https://openlibrary.org/isbn/9780723438328 [w3r2 2026-08-14] LEADING REFERENCE IS WRONG FOR THIS FIGURE (10x). The served 20 micrograms/kg is CORRECT and does not move - Carpenter 6th ed Table 5.7 (Hormones and Steroids Used in Birds) prints "20 ug/kg PO q12-24h43,159,391 | Most species, including psittacines, pigeons, and raptors", and BSAVA Small Animal Formulary Part B printed p.179 independently prints "Birds: 0.02 mg/kg p.o. q12-24h. Dissolve 1 mg in 28.4 ml water and give 0.4-0.5 ml/kg q12-24h." But the cited leading reference - Bailey TA and Apo MM, Pharmaceutics commonly used in avian medicine, in Samour J ed, Avian Medicine 3rd ed, Mosby Elsevier, 2016:637-678 - prints levothyroxine TWICE at printed p.665 and BOTH times at 0.2 mg/kg PO q12-24h, ten times the served figure. LEAD WITH the BSAVA Part B monograph, which we hold and which prints the exact served figure, and keep Bailey and Apo only as a recorded disagreement so it is not silently re-added.

· 43. Bailey TA, Apo MM. Pharmaceutics commonly used in avian medicine. In: Samour J, eds. Avian Medicine, 3rd ed., Mosby Elsevier, Edinburgh, Scotland; 2016:637-678. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.463 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.7 (Hormones and Steroids Used in Birds). The copy held is an ebook conversion with no printed page numbers, so the table — not the page — is the citable location. — SOURCE EDITION: Carpenter's Exotic Animal Formulary — ISBN 9780323833929, https://openlibrary.org/isbn/9780323833929; Avian Medicine (Samour) — ISBN 9780723438328, https://openlibrary.org/isbn/9780723438328

· 781. Rosenthal KL, Johnston M. Hypothyroidism in a red-lored Amazon (Amazona autumnalis). Proc Annu Conf Assoc Avian Vet; 2003:33-36. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.463 — Carpenter's Exotic Animal Formulary 6th ed, Table 5.7 (Hormones and Steroids Used in Birds). The copy held is an ebook conversion with no printed page numbers, so the table — not the page — is the citable location. — SOURCE EDITION: Carpenter's Exotic Animal Formulary — ISBN 9780323833929, https://openlibrary.org/isbn/9780323833929 — SOURCE ROW: Carpenter's Exotic Animal Formulary 6th ed, corpus p.463 — "Levothyroxine (l-thyroxine) ... 5-200 ug/kg PO ... Amazon parrots ... May induce molt; monitor […]"

· Ewringmann A, Gloeckner B. Leitsymptome bei Meerschweinchen, Chinchilla und Degu, Enke, Stuttgart, Germany; 2012. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.801 — Carpenter's Exotic Animal Formulary 6th ed, Table 9.7 (Miscellaneous Agents Used in Rodents). The copy held is an ebook conversion with no printed page numbers, so the table — not the page — is the citable location. — SOURCE EDITION: Carpenter's Exotic Animal Formulary — ISBN 9780323833929, https://openlibrary.org/isbn/9780323833929

· Franco KH and Hoover JP (2009) Leveothyroxine as a treatment for presumed hypothyroidism in an adult male African spurred tortoise. Journal of Herpetological Medicine and Surgery 19(2), 47-49 — Source: BSAVA Small Animal Formulary, 10th Ed, Part B: Exotic Pets, p.194 — SOURCE EDITION: BSAVA Small Animal Formulary, Part B — Exotic Pets — ISBN 9781910443712, https://openlibrary.org/isbn/9781910443712

· Hadfield CA, Clayton LA, Clancy MM. Proliferative thyroid lesions in three diplodactylid geckos: Nephrurus amyae, Nephrurus levis, and Oedura marmorata. J Zoo Wildl Med. 2012,43:131-140. - Carpenter's Exotic Animal Formulary 6th ed, Table 4.8 (Hormones and Steroids Used in Reptiles): 'Levothyroxine | 0.02 mg/kg PO q48h172 | Geckos/post thyroidectomy, lifetime management'. SOURCE EDITION: Carpenter's Exotic Animal Formulary - ISBN 9780323833929. The entry 'Clinical Guide to Fish Medicine - ISBN 9781119259558' is REMOVED - no fish text bears on a gecko thyroid row.

· Hadfield CA, Clayton LA, Clancy MM. Proliferative thyroid lesions in three diplodactylid geckos: Nephrurus amyae, Nephrurus levis, and Oedura marmorata. J Zoo Wildl Med. 2012;43:131-140. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.260 doi:10.1638/2011-0106.1 — Carpenter's Exotic Animal Formulary 6th ed, Table 4.8 (Hormones and Steroids Used in Reptiles). The copy held is an ebook conversion with no printed page numbers, so the table — not the page — is the citable location. — SOURCE EDITION: Carpenter's Exotic Animal Formulary — ISBN 9780323833929, https://openlibrary.org/isbn/9780323833929; Clinical Guide to Fish Medicine — ISBN 9781119259558, https://openlibrary.org/isbn/9781119259558

· Meredith A. BSAVA Small Animal Formulary: Part B: Exotic Pets, British Small Animal Veterinary Association, Quedgeley, Gloucester, UK; 2015. — Source: Carpenter's Exotic Animal Formulary, 6th Ed, p.801 — Carpenter's Exotic Animal Formulary 6th ed, Table 9.7 (Miscellaneous Agents Used in Rodents). The copy held is an ebook conversion with no printed page numbers, so the table — not the page — is the citable location. — SOURCE EDITION: BSAVA Small Animal Formulary, Part B — Exotic Pets — ISBN 9781910443712, https://openlibrary.org/isbn/9781910443712; Carpenter's Exotic Animal Formulary — ISBN 9780323833929, https://openlibrary.org/isbn/9780323833929

· Scott-Moncrieff JC. Chapter 3: Hypothyroidism. In: Canine and Feline Endocrinology. 4th ed. Elsevier Saunders; 2015.; Peterson ME, Carothers MA, Gamble DA, Rishniw M. Spontaneous primary hypothyroidism in 7 adult cats. J Vet Intern Med. 2018;32(6):1864-1873. doi:10.1111/jvim.15417 — Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.778 (2026-08-01). — Plumb's 10th ed (held) printed p.749, Levothyroxine monograph spanning p.749-751; page located 2026-08-05 from the book's own running heads, verified to name the drug in its body text. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207

· Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.777 (2026-08-01). — Plumb's 10th ed (held) printed p.749, Levothyroxine monograph spanning p.749-751; page located 2026-08-05 from the book's own running heads, verified to name the drug in its body text. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207

Levothyroxine

Drug Class

Routes

Indications

Mechanism of Action

Side effects & warnings

Species with Levothyroxine dosing data (16 dose rules)

Evidence levels across 16 dose rules

Backed by 15 published sources

Sample dosing (2 of 16 cited rules)

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Levothyroxine

Drug Class

Routes

Indications

Mechanism of Action

Side effects & warnings

Species with Levothyroxine dosing data (16 dose rules)

Evidence levels across 16 dose rules

Backed by 15 published sources

Sample dosing (2 of 16 cited rules)

Upgrade for Full Details

More Endocrine drugs