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  • Doley Road,
  • Byford,
  • Western Australia,
  • Phone: (040) 735-2836

Levothyroxine/Thyroxine

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medicationWhy has my veterinarian prescribed this medicine?

Levothyroxine (also called Thyroxine) is used to treat low thyroid levels. This medication belongs to the general group of medicines called hormones. It is used to provide replacement thyroid hormone when the thyroid gland does not produce enough (hypothyroid).

How does this medicine work?

Levothyroxine is an optical isomer of thyroxine, the main normal secretory product of the thyroid gland. Some of the medicine is de-iodinated in peripheral tissues to the more active tri-iodothyronine.

How do I give this medication?

- Give this medicine to your pet as directed by your veterinarian. READ THE LABEL CAREFULLY.

-  Try to give this medication at about the same time(s) each day. It may be better to give the dose as a single daily dose than in divided daily doses.

- DO NOT give your pet more medicine than directed and DO NOT give the drug more often than directed.

- DO NOT discontinue the medication without first checking with your veterinarian. Contact your veterinarian in advance if your pet needs a repeat prescription.

- Try not to miss giving any doses.

- The correct dose depends on the condition of your pet. Your veterinarian will need to monitor your pet and the results of blood tests.

What if I miss giving a dose?

Give the dose as soon as possible. If it is almost time for the next dose, skip the missed dose, and continue with the regular schedule. Do not give the pet two doses at once.

How do I store this medicine?

Keep this medicine out of reach of children. Store this medicine in a cool, dry place at room temperature. Store away from heat and direct sunlight. Do not store this medicine in the bathroom, near the kitchen sink or in damp places. The medicine may break down if exposed to heat or moisture.

Potential side effects

- When administered at the appropriate dose, there should not be any adverse effects.

- Rarely the following side-effects may be seen: excessive drinking, diarrhoea, excessive urination, fast heart rate, excessive ingestion of food, nervousness, excessive panting and weight loss. Notify your veterinarian if these symptoms occur.

- Other side effects may occur. If the pet experiences anything unusual, contact your veterinarian.

Possible drug interactions

- Make sure to tell your veterinarian what other medication you are giving to your pet.

- Drugs may interact such that they can cause an increased or decreased effect or side effects. Although drug interactions may occur, it does not mean that there is necessarily a high risk of any of these occurring.

- Contact your veterinarian if your pet experiences any unusual reactions when different medications are given together.

© Copyright 2025 LifeLearn Inc. Used and/or modified with permission under license. This content written by LifeLearn Animal Health (LifeLearn Inc.) is licensed to this practice for the personal use of our clients. Any copying, printing or further distribution is prohibited without the express written consent of LifeLearn. This content does not contain all available information for any referenced medications and has not been reviewed by the FDA Center for Veterinary Medicine, or Health Canada Veterinary Drugs Directorate. This content may help answer commonly asked questions, but is not a substitute for medical advice, or a proper consultation and/or clinical examination of your pet by a veterinarian. Please contact your veterinarian if you have any questions or concerns about your pet’s health. Created on Jul 29, 2015.