Hypothyroidism is one of the most commonly diagnosed endocrine disorders in dogs and is typically managed with lifelong thyroid hormone replacement prescribed by a veterinarian. The condition occurs when the thyroid gland does not produce sufficient thyroid hormone to support normal metabolic function.
Veterinarians most often use levothyroxine sodium for dogs to manage hypothyroidism. Because long-term treatment relies on consistent daily administration and individualized dosing, the prescribed formulation and dose accuracy play an important role in supporting stable management over time.
Many dogs do well on FDA-approved commercial levothyroxine products, while others may require adjustments or alternative formulations based on their individual needs.
This article explains the effects of hypothyroidism in dogs, how it is diagnosed, why levothyroxine is used and how veterinary compounding can support compliance when standard products are not the best fit.
Hypothyroidism in dogs occurs when the thyroid gland produces inadequate amounts of thyroid hormone, most commonly thyroxine (T4). Thyroid hormones regulate metabolism and influence many body systems, including:
Hypothyroidism symptoms in dogs can include:
Because these signs can overlap with other conditions, diagnosis is based on laboratory testing interpreted alongside clinical findings.
Veterinarians determine whether hypothyroidism is present and whether treatment is appropriate based on the individual dog’s history, exam findings and thyroid hormone testing.
Diagnosis typically involves blood testing to evaluate thyroid hormone levels. Depending on the clinical picture, veterinarians may assess:
Accurate diagnosis is essential before initiating therapy, as inappropriate supplementation can cause adverse effects.
Levothyroxine sodium for dogs is a synthetic thyroid hormone used to replace deficient thyroxine levels under veterinary supervision. Levothyroxine is considered the standard prescription medication for canine hypothyroidism.
Veterinarians determine whether levothyroxine sodium for dogs is appropriate, the formulation and strength and how response is monitored over time.
Thyroid hormone replacement is typically a lifelong therapy. Maintaining stable hormone levels depends on consistent daily administration and accurate dosing tailored to the individual dog.
Veterinarians consider multiple factors when determining and adjusting therapy over time, including:
Because commercially manufactured tablets are available only in fixed strengths, some dogs may fall between standard doses or require adjustments that are difficult to achieve without modification.
FDA-approved commercial levothyroxine products, like Thyro-tabs and others, are often the first-line option for dogs with hypothyroidism. Compounded formulations may be discussed when commercial options do not meet a dog’s specific dosing or administration needs.
For medications like levothyroxine that are given daily and often for life, compounding can support long-term adherence.
Veterinarians may consider compounded levothyroxine when:
Compounded formulations are prepared only with a valid prescription and are dispensed according to veterinarian direction.
Common compounded forms include:
The choice of formulation depends on the veterinarian’s prescription and the dog’s specific needs.
Managing hypothyroidism is an ongoing process rather than a one-time decision. Veterinarians typically reassess dogs receiving thyroid hormone replacement through follow-up examinations and laboratory testing to evaluate response and ensure hormone levels remain appropriate.
Adjustments may be made as dogs age, experience weight or health changes or encounter administration challenges. As mentioned, consistency in dosing and formulation plays an important role in maintaining long-term stability.
Can I Get Pet Medication Delivery to My House? →
Levothyroxine sodium for dogs is the most commonly prescribed medication for canine hypothyroidism. It replaces deficient thyroid hormone and is prescribed and monitored by a veterinarian.
No. Dosing of levothyroxine sodium for dogs is individualized based on the patient’s size, health status and laboratory results. Veterinarians determine dosing and make adjustments as needed.
T3 is not usually prescribed because healthy dogs naturally convert thyroxine (T4) into triiodothyronine (T3) within peripheral tissues as needed. Providing levothyroxine allows the body to regulate this conversion locally, which supports more physiologic thyroid hormone balance. Direct T3 supplementation may lead to fluctuations in hormone levels and is typically reserved for specific, veterinarian-directed situations rather than routine management.
Yes. When prescribed by a veterinarian, levothyroxine sodium for dogs may be compounded to provide customized strengths or alternative dosage forms that support consistent administration.
Yes—as long as they are properly formulated, accurately prepared, and administered with veterinary oversight. Compounded medications are prescribed by veterinarians when clinically appropriate.
Choosing a PCAB®-accredited compounding pharmacy can add an additional layer of assurance, as these pharmacies are independently reviewed for their facilities, processes, ingredient sourcing, quality controls and ongoing compliance with compounding standards.
No. Any changes to thyroid medication should be made only under the guidance of a veterinarian who is monitoring your dog’s condition.
Hypothyroidism is a common and manageable condition in dogs when appropriately diagnosed and treated under veterinary supervision.
Levothyroxine sodium for dogs remains the standard therapy, and because treatment is often lifelong, accurate dosing and consistent administration are important considerations.
Veterinary compounding may offer flexibility when commercial products do not meet a dog’s individual needs. Mixlab compounds levothyroxine and related formulations based on your veterinarian’s prescription, supporting individualized care for dogs with hypothyroidism.
Shop brand name and compounded levothyroxine medications for your dog at Mixlab. Once you place your order, our pharmacy team coordinates with your veterinarian for prescription approval, prepares the medication as directed and ships it fast and free to your doorstep.