Hypothyroidism in dogs: treatment, monitoring and costs
Checked against veterinary references: October 2026
Short answer
Hypothyroidism means the thyroid makes too little hormone, causing weight gain, low energy, coat and skin problems. It is treated with levothyroxine tablets, usually once or twice a day for life, with blood tests to set the dose. Energy often improves within a couple of weeks and coat and skin over a few months. Human generic levothyroxine can be filled at a regular pharmacy with your vet’s prescription.
Hypothyroidism vs Cushing’s disease in dogs
- Typical signsHypothyroidism: Weight gain, low energy, seeking warmth, thinning coat on the body and tail, skin infectionsCushing’s disease: Drinking and urinating more, big appetite, panting, pot belly, thin skin
- Thirst and urinationHypothyroidism: Usually normalCushing’s disease: Increased
- Typical dogsHypothyroidism: Middle-aged, often medium to large breedsCushing’s disease: Middle-aged to older, often smaller breeds
- DiagnosisHypothyroidism: Thyroid blood tests such as T4, free T4 and TSHCushing’s disease: ACTH stimulation or dexamethasone suppression tests
- TreatmentHypothyroidism: Daily levothyroxine tabletsCushing’s disease: Daily trilostane capsules; surgery for some tumors
- OutlookHypothyroidism: Excellent with lifelong treatmentCushing’s disease: Controlled long term in most dogs
| Feature | Hypothyroidism | Cushing’s disease |
|---|---|---|
| Typical signs | Weight gain, low energy, seeking warmth, thinning coat on the body and tail, skin infections | Drinking and urinating more, big appetite, panting, pot belly, thin skin |
| Thirst and urination | Usually normal | Increased |
| Typical dogs | Middle-aged, often medium to large breeds | Middle-aged to older, often smaller breeds |
| Diagnosis | Thyroid blood tests such as T4, free T4 and TSH | ACTH stimulation or dexamethasone suppression tests |
| Treatment | Daily levothyroxine tablets | Daily trilostane capsules; surgery for some tumors |
| Outlook | Excellent with lifelong treatment | Controlled long term in most dogs |
Treatment with levothyroxine
Levothyroxine replaces the missing hormone. Veterinary brands such as Thyro-Tabs and human generics contain the same medicine, though dogs need much higher doses than people, so always follow your vet’s dose. Give it at the same times each day, consistently with or without food. See our levothyroxine guide.
Monitoring
About four weeks after starting or changing the dose, your vet checks a blood thyroid level, usually four to six hours after a pill, when levels peak. Once the dose is right, checks are typically every six to twelve months.
Signs of too much hormone
- Restlessness, panting or a racing heart.
- Increased thirst, urination or appetite with weight loss.
- Diarrhea or vomiting.
- Call your vet if these appear; the dose may need lowering.
What improves, and when
Energy and alertness often improve within one to two weeks. Weight comes down over a few months, and the coat and skin can take several months to recover fully. Skin infections that came with the condition may need their own treatment.
A low result is not always hypothyroidism
Other illnesses and some medicines, including steroids and phenobarbital, can lower thyroid test results in dogs whose thyroid is healthy. That is why vets confirm with more than one test before starting lifelong treatment.
Costs
Levothyroxine is an inexpensive generic, and a regular pharmacy can fill human tablets with your vet’s prescription, often for less than veterinary brands; ask your vet which product and strength to use. Periodic blood tests are the other ongoing cost. See which pet medicines a regular pharmacy can fill.
What about cats?
Cats rarely develop an underactive thyroid on their own; it is far more common for cats to have an overactive one. See hyperthyroidism in cats.
Frequently asked questions
Can hypothyroidism in dogs be cured?
No, but it is one of the most treatable conditions in dogs. With daily levothyroxine and periodic blood tests, most dogs live normal lives.
Can my dog take human levothyroxine?
Yes, when your vet prescribes it. It is the same medicine, though dogs need much higher doses than people, and a regular pharmacy can fill the prescription.
How long until my dog improves?
Energy often improves within one to two weeks; weight, coat and skin over several months.
What if I miss a dose?
Give it when you remember unless the next dose is near, and never double up. An occasional missed dose is not dangerous.