Product details
Thyro-L (levothyroxine sodium powder, USP) is indicated for use in horses to correct conditions associated with low circulating thyroid hormone (hypothyroidism).
- The original levothyroxine sodium powder supplement for horses
- Contains Levothyroxine Sodium powder, USP (T-4) for predictable therapeutic results
- Highly reliable and stable thyroxine replacement hormone
- Adjunct treatment for weight loss in horses with insulin resistance
- Aids in the prevention of laminitis and hyperlipidemia
Product sourced directly from the manufacturer or their approved distributor. Guaranteed genuine product backed by the manufacturer.
For
Horses
Active ingredient(s)
Levothyroxine sodium
Inactive ingredients
Complete inactive ingredients list not provided by manufacturer.
Brand name
Thyro-L
Drug class
Thyroid hormone
Product flavoring
The manufacturer states that this product is formulated in a palatable flavor base that is eagerly accepted by horses; however, specific flavoring information is not provided.
Manufacturer
LLOYD, Inc.
Product strength & size
Thyro-L Powder contains 1000 mg of levothyroxine sodium, USP in each pound (453.6 grams) of powder. Each level teaspoonful contains approximately 12 mg of T-4. A teaspoon measuring scoop is included in each bottle.
Please ensure the selected product is appropriate for your animal, as recommended by your veterinarian. For current availability, please refer to the product selection above.
Usage
For additional product information, please refer to the product label or consult your veterinarian.
Thyro-L should be given orally as directed by your veterinarian. Wash your hands thoroughly with soap and water before and after handling the medication. Please consult your veterinarian before making any changes or discontinuing the prescribed dosing schedule.
Missed doses
Administer 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 more medication than prescribed or two doses at once.
If you have questions about your animal’s prescribed dosing schedule (e.g., timing, interval), please consult your veterinarian.
Storage
Store in a cool, dry place at a controlled room temperature and protect from light. Avoid excessive heat (104°F). Keep in a secure location out of the reach of children and animals.
Exposure to extreme temperatures, light, or moisture can affect the integrity and effectiveness of medications. Always store medications properly (e.g., away from the bathroom, kitchen sink, or other damp places).
Side effects
This medication is generally well-tolerated, and side effects are uncommon when administered at the appropriate dosage. Dosages should be individualized and animals should be monitored daily for clinical signs of hyperthyroidism or hypersensitivity.
Clinical signs of hyperthyroidism can occur at high doses, including (but not limited to) rapid or excessive weight loss, increased heart and/or respiratory rates, and behavioral changes (e.g., agitation, excitability, restlessness).
Notify your veterinarian if your horse experiences any of the effects described above, or if you notice any other side effects that are persistent or troublesome.
If you notice anything unusual, please consult your veterinarian.
Precautions
Before using this product, please review the product label and prescribing information for important safety information, including any relevant warnings and precautions.
For oral use in horses only. Keep out of reach of children.
Use with caution in animals with clinically significant heart disease, hypertension, or other complications for which a sharply increased metabolic rate might prove hazardous. Use in pregnant mares has not been evaluated.
Do not administer this medication to animals with a known or suspected allergy/hypersensitivity to any levothyroxine product, including Thyro-L, or any of its ingredients. Allergic reactions to medications may occur. Please inform Vetsource and your veterinarian if your animal has any known sensitivities or allergies, especially to medications and supplements.
If your horse displays symptoms of an allergic reaction, discontinue therapy and call your veterinarian immediately or seek emergency veterinary attention. Symptoms may include (but are not limited to): swollen lips, tongue, face, or airways; difficulty breathing; agitation; profuse salivation; and widespread hives or itching.
Drug and food interactions
The following drugs* may have potential interactions with this medication:
antacids (containing aluminum, calcium, and/or magnesium), antidiabetic agents (including insulins), beta blockers (e.g., sotalol), corticosteroids (e.g., dexamethasone, prednisone), digoxin, fiber supplements (or high-fiber diets), fluoroquinolone antibiotics (e.g., ciprofloxacin), iron supplements, omeprazole, phenobarbital, SSRIs (e.g., fluoxetine), sucralfate, and warfarin.
*NOTE: This may not be a comprehensive list. Contact your veterinarian if your animal experiences any unusual reactions when multiple medications and/or supplements are given together.
As with all medications, please consult your veterinarian if you have any questions or concerns prior to use. Please ensure your veterinarian is aware of all medications, supplements, and over-the-counter (OTC) products that your horse is currently using. Your veterinarian may prescribe multiple medications, even if a potential drug interaction may occur. In these instances, your veterinarian may adjust the dosages or monitor your horse more closely.
Adverse reactions
If you are concerned that your horse has experienced an adverse reaction to this medication, please contact the manufacturer LLOYD, Inc. at 1-800-831-0004 or Vetsource Pet Owner Care at 877-738-4443.
Overdose
If you have any reason to suspect an overdose, call your doctor/veterinarian or the appropriate poison control resource immediately.
For humans:
The national toll-free Poison Help line, 1-800-222-1222, will connect you to your local poison center in case of emergency. This service is available nationwide and in most U.S. territories.
For animals:
The ASPCA Animal Poison Control Center is available 24 hours a day, 365 days a year at 888-426-4435.
Pet Poison Helpline® also provides a 24/7 animal poison control service at 855-764-7661.
*Please note: this information is for third-party services and is provided for convenience in case of potential poison-related emergencies. There may be consultation fee for these services.
Disclaimer
The content provided on this page is NOT medical advice.
All content, including the images and product description above, is intended for general informational purposes only and should not be considered a substitute for professional veterinary consultation, diagnosis, or treatment.
For additional information about this product and how it fits into your horse's individual treatment plan, please consult your veterinarian.
Last revised: 3/09/2026
-
Description
Product detailsThyro-L (levothyroxine sodium powder, USP) is indicated for use in horses to correct conditions associated with low circulating thyroid hormone (hypothyroidism).- The original levothyroxine sodium powder supplement for horses
- Contains Levothyroxine Sodium powder, USP (T-4) for predictable therapeutic results
- Highly reliable and stable thyroxine replacement hormone
- Adjunct treatment for weight loss in horses with insulin resistance
- Aids in the prevention of laminitis and hyperlipidemia
Product sourced directly from the manufacturer or their approved distributor. Guaranteed genuine product backed by the manufacturer.ForHorsesActive ingredient(s)Levothyroxine sodiumInactive ingredientsComplete inactive ingredients list not provided by manufacturer.Brand nameThyro-LDrug classThyroid hormoneProduct flavoringThe manufacturer states that this product is formulated in a palatable flavor base that is eagerly accepted by horses; however, specific flavoring information is not provided.ManufacturerLLOYD, Inc.Product strength & sizeThyro-L Powder contains 1000 mg of levothyroxine sodium, USP in each pound (453.6 grams) of powder. Each level teaspoonful contains approximately 12 mg of T-4. A teaspoon measuring scoop is included in each bottle.Please ensure the selected product is appropriate for your animal, as recommended by your veterinarian. For current availability, please refer to the product selection above.UsageFor additional product information, please refer to the product label or consult your veterinarian.Thyro-L should be given orally as directed by your veterinarian. Wash your hands thoroughly with soap and water before and after handling the medication. Please consult your veterinarian before making any changes or discontinuing the prescribed dosing schedule.Missed dosesAdminister 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 more medication than prescribed or two doses at once.If you have questions about your animal’s prescribed dosing schedule (e.g., timing, interval), please consult your veterinarian.StorageStore in a cool, dry place at a controlled room temperature and protect from light. Avoid excessive heat (104°F). Keep in a secure location out of the reach of children and animals.Exposure to extreme temperatures, light, or moisture can affect the integrity and effectiveness of medications. Always store medications properly (e.g., away from the bathroom, kitchen sink, or other damp places).Side effectsThis medication is generally well-tolerated, and side effects are uncommon when administered at the appropriate dosage. Dosages should be individualized and animals should be monitored daily for clinical signs of hyperthyroidism or hypersensitivity.Clinical signs of hyperthyroidism can occur at high doses, including (but not limited to) rapid or excessive weight loss, increased heart and/or respiratory rates, and behavioral changes (e.g., agitation, excitability, restlessness).Notify your veterinarian if your horse experiences any of the effects described above, or if you notice any other side effects that are persistent or troublesome.If you notice anything unusual, please consult your veterinarian.PrecautionsBefore using this product, please review the product label and prescribing information for important safety information, including any relevant warnings and precautions.For oral use in horses only. Keep out of reach of children.Use with caution in animals with clinically significant heart disease, hypertension, or other complications for which a sharply increased metabolic rate might prove hazardous. Use in pregnant mares has not been evaluated.Do not administer this medication to animals with a known or suspected allergy/hypersensitivity to any levothyroxine product, including Thyro-L, or any of its ingredients. Allergic reactions to medications may occur. Please inform Vetsource and your veterinarian if your animal has any known sensitivities or allergies, especially to medications and supplements.If your horse displays symptoms of an allergic reaction, discontinue therapy and call your veterinarian immediately or seek emergency veterinary attention. Symptoms may include (but are not limited to): swollen lips, tongue, face, or airways; difficulty breathing; agitation; profuse salivation; and widespread hives or itching.Drug and food interactionsThe following drugs* may have potential interactions with this medication: antacids (containing aluminum, calcium, and/or magnesium), antidiabetic agents (including insulins), beta blockers (e.g., sotalol), corticosteroids (e.g., dexamethasone, prednisone), digoxin, fiber supplements (or high-fiber diets), fluoroquinolone antibiotics (e.g., ciprofloxacin), iron supplements, omeprazole, phenobarbital, SSRIs (e.g., fluoxetine), sucralfate, and warfarin.*NOTE: This may not be a comprehensive list. Contact your veterinarian if your animal experiences any unusual reactions when multiple medications and/or supplements are given together.As with all medications, please consult your veterinarian if you have any questions or concerns prior to use. Please ensure your veterinarian is aware of all medications, supplements, and over-the-counter (OTC) products that your horse is currently using. Your veterinarian may prescribe multiple medications, even if a potential drug interaction may occur. In these instances, your veterinarian may adjust the dosages or monitor your horse more closely.Adverse reactionsIf you are concerned that your horse has experienced an adverse reaction to this medication, please contact the manufacturer LLOYD, Inc. at 1-800-831-0004 or Vetsource Pet Owner Care at 877-738-4443.OverdoseIf you have any reason to suspect an overdose, call your doctor/veterinarian or the appropriate poison control resource immediately.For humans:The national toll-free Poison Help line, 1-800-222-1222, will connect you to your local poison center in case of emergency. This service is available nationwide and in most U.S. territories.For animals:The ASPCA Animal Poison Control Center is available 24 hours a day, 365 days a year at 888-426-4435.Pet Poison Helpline® also provides a 24/7 animal poison control service at 855-764-7661.*Please note: this information is for third-party services and is provided for convenience in case of potential poison-related emergencies. There may be consultation fee for these services.DisclaimerThe content provided on this page is NOT medical advice.All content, including the images and product description above, is intended for general informational purposes only and should not be considered a substitute for professional veterinary consultation, diagnosis, or treatment.For additional information about this product and how it fits into your horse's individual treatment plan, please consult your veterinarian.Last revised: 3/09/2026 -
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