Chronic Diseases & Special Conditions
Hypothyroidism in Dogs: Diet and Weight Control
The most common signs of hypothyroidism are unexplained weight gain and hair loss. We show what diet can do in addition to treatment.
When to see a vet IMMEDIATELY
- •Blood in stool or vomit
- •Lethargy, not drinking, or not eating for 24+ hours
- •Repeated vomiting, especially if water won't stay down
- •Swollen or painful abdomen, whimpering
- •Diarrhea lasting more than 3 days, or worsening symptoms
This article is informational and does not replace veterinary examination.
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Hypothyroidism in Dogs: Diet and Weight Control
Hypothyroidism is one of the most common hormonal diseases in dogs. The thyroid gland produces fewer hormones, which slows down the entire metabolism. Diet does not cure it, but body weight, skin, and coat condition are largely dietary matters.
Typical Signs
- Unexplained weight gain with unchanged food portions
- Fatigue, less enthusiasm for walks
- Symmetrical hair loss, especially on the torso and tail
- Dry, flaky skin, recurrent skin infections
- Sensitivity to cold
- Slower heart rate
Predisposed breeds: Golden Retriever, Labrador, Doberman, Boxer, Irish Setter, Dachshund. Most commonly occurs between 4–10 years of age.
Diagnosis is a Veterinary Task
Blood tests are required (T4, fT4, TSH). Symptoms are very similar to obesity, Cushing's syndrome, and allergic dermatitis, so never start "thyroid treatment" with diet without a diagnosis. The basis of treatment is daily hormone replacement (levothyroxine); no food can substitute for this.
4 Tasks of the Diet
1. Weight Control: The Most Important
Due to slowed metabolism, the same portion causes weight gain. After treatment is established, the dog often returns to normal on its own, but until then:
- Recalculate daily calories for the target weight, not the current weight
- Reduce by 10–15% and portion with a scale
- Monitor with weekly weight measurements: a safe rate is 0.5–1% of body weight per week
2. High Protein, Moderate Fat
- Protein: 25–30% on a dry matter basis, to avoid muscle loss during weight reduction
- Fat: 10–14%, because hypothyroid dogs often have elevated blood fat levels (hyperlipidemia)
3. Omega-3 for Skin and Coat
- 50–100 mg EPA + DHA / kg body weight / day
- Hair regrowth takes 2–4 months after hormone replacement is established; omega-3 supports this
4. Iodine: Neither Too Little Nor Too Much
A complete, FEDIAF/AAFCO compliant food contains sufficient iodine. Do not give iodine supplements or seaweed preparations on your own: excessive iodine intake impairs thyroid function and confuses lab values.
What to Watch for with Medication
- Levothyroxine should generally be given on an empty stomach; food reduces its absorption. Maintain the timing specified by your veterinarian and do not change it daily.
- Soy and large amounts of calcium also reduce absorption, so do not mix the tablet into dairy products.
- Control blood tests usually after 4–8 weeks, then annually.
When to See a Veterinarian Immediately
- If the dog suddenly becomes very tired, weak, and has a low body temperature
- If the dog is restless, pants a lot, or loses weight during treatment (may be a sign of overdose)
This information is for informational purposes only and does not replace a veterinary examination.
Free tool — no sign-up
Enter weight and activity level — 10 seconds and you get the daily portion.
This is general information and does not replace a veterinary diagnosis.
This guide was compiled based on the expert input of Reka Fazekas-Birizdo canine nutritionist.
Certified Canine Nutritionist
