Updated October 31, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
When a dog is diagnosed with hypothyroidism, thyroid hormone replacement can make a meaningful difference. The standard treatment is prescription levothyroxine, but the right dose and monitoring schedule depend on your dog. This article deliberately does not provide a dosing chart: changing thyroid medication without veterinary advice can cause significant problems.
First confirm the diagnosis
Low energy, weight gain, thinning fur and recurring skin trouble can occur with hypothyroidism, but they are not specific to it. A low total T4 result alone does not establish the diagnosis, because illness and some medications can also reduce T4. Veterinarians interpret the history and appropriate thyroid tests together before prescribing lifelong treatment.
How is levothyroxine given?
Different veterinary levothyroxine products have different labeled schedules. The veterinarian selects the product and amount for your dog and explains when to give it. Be consistent about giving it with or without food, because food can change absorption. Don’t switch formulations, split a dose or double up after a missed tablet unless your veterinary team instructs you.
Why are follow-up blood tests necessary?
Thyroid hormone levels are usually reassessed after starting treatment or changing the dose. The timing of blood collection relative to a dose matters, so follow the clinic’s instructions rather than scheduling a random draw. The veterinarian uses both laboratory results and clinical improvement to decide whether an adjustment is appropriate.
What improvements or side effects should you watch?
Energy may improve within weeks, while skin and coat changes often recover more gradually. Too much thyroid hormone or an adverse reaction may show up as restlessness, excessive drinking, increased urination, gastrointestinal upset or other unexpected changes. Contact the clinic if these develop. A dog with heart disease may need closer supervision when thyroid treatment begins.
Read how improvement after treatment is monitored and signs of thyroid disease in dogs.
Veterinary references
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.