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Levothyroxine Sodium

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Drug Details

  • Drug Name: Levothyroxine Sodium
  • Common Name: Soloxine, Thyro-Tabs, Pala-Tech, Thyrovet (vet forms)
  • Generics: Generics available
  • Drug Type: T4 replacement
  • Used For: Underactive Thyroid
  • Species: Dogs, Cats
  • Administered: Tablets, Chewable Tablets
  • How Dispensed: Prescription Only
  • Available Forms: 0.1mg, 0.2mg, 0.3mg, 0.4mg, 0.5mg, 0.6mg, 0.7mg, 0.8mg, 0.9mg, or 1.0mg Tablets
  • FDA Approved: Yes



Levothyroxine Sodium is a synthetic thyroid hormone, usually as a lifelong medication, for animals that have an underactive thyroid (i.e., animals with hypothyroidism).


Dosage and Administration


Always follow the dosage instructions from your veterinarian.


The initial recommended dose is 0.1mg/10 lb of body weight in a twice daily dosing. Dosage will need to be monitored and adjusted to achieve the correct maintenance dose. Blood work should be kept up to date to ensure proper dosing.


Missed Dose?


If a dose of Levothyroxine Sodium is missed, give the dose as soon as you remember. If you remember when it is almost time for the next dose, skip the one you missed and get back on your regular schedule. Do NOT double the dosing.


Possible Side Effects


When given at the correct dose, there are no known side effects associated with Levothyroxine Sodium.  High doses of Levothyroxine Sodium may cause: 

  • Excessive thirst
  • Large amounts of urine production
  • Increased appetite
  • Personality change
  • Reduced heat tolerance
  • Personality change


Immediately contact your veterinarian if you think your dog has any medical problems or side effects while taking Levothyroxine sodium.




Differences exist between different brands; do not change brands if possible.  If you need to change, please consult with your veterinarian as blood work may need to be rechecked to verify correct dosing.


Use with caution with animals that have heart disease, hypertension or other complications for which a sharply increased metabolic rate could be hazardous. Do not use in animals that have a hyperactive thyroid (produce too much thyroid hormone). Do not give Levothyroxine sodium if your pet is allergic to it.


Use in pregnant and lactating animals has not been evaluated.




Store in a tight, light-resistant container.  Store at controlled room temperature 59-86oF.


Keep this, and all medications, out of reach of children.


Drug Interactions


Consult your veterinarian when giving other medications with Levothyroxine Sodium as interactions may occur.  Possible interactions may be noticed but not limited to epinephrine, norepinephrine, insulin, estrogens, warfarin, digoxin, and vitamins or supplements.


Signs of Toxicity/Overdose


Overdose of Levothyroxine Sodium may cause: 

  • Excessive thirst
  • Large amounts of urine production
  • Increased appetite
  • Personality change
  • Reduced heat tolerance
  • Personality change


If you suspect or know you dog has had an overdose, please contact your veterinarian or emergency vet clinic immediately.

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