When a dog has confirmed hypothyroidism, the usual treatment is replacement of the thyroid hormone the body no longer produces adequately. Most dogs can feel much better with consistent care, but starting treatment without a reliable diagnosis can hide other problems.
Confirm the diagnosis first
Low energy, weight gain and hair loss are common clues, not proof. A low total T4 value may occur during another illness or as a medication effect. A veterinarian interprets symptoms with thyroid tests, sometimes including free T4 and TSH, and considers the dog’s breed and health history before prescribing.
How levothyroxine helps
Levothyroxine is a prescription thyroid hormone replacement, and FDA-approved veterinary products are available. Your vet selects the product and dose for the individual dog. Give doses consistently in relation to meals as instructed; food can affect how much hormone is absorbed. Do not swap products, double missed doses or stop treatment on your own.
Expect ongoing monitoring
Energy often improves before coat and skin changes resolve. Veterinarians commonly check thyroid levels after treatment starts or doses change, then at longer intervals once stable. The timing of a blood sample relative to the pill is important, so ask the clinic exactly when to give medication before a monitoring appointment.
When to call about a possible side effect
Marked restlessness, panting, vomiting, diarrhea, unusual thirst, fast heartbeat or weight loss can accompany excessive thyroid replacement or another illness. Call the prescribing veterinarian rather than making an independent dose change. For day-to-day guidance see how thyroid medicine works and living with a hypothyroid dog.
Veterinary references
- AAHA: Canine hypothyroidism
- AAHA: Diagnostic testing and monitoring
- FDA: Approved treatments for hypothyroidism in dogs
For education only. Thyroid tests and treatment must be interpreted by a veterinarian.
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.