Levothyroxine
Thyro-Tabs, ThyroKare, Synthroid (veterinary and human) · generic levothyroxine
Levothyroxine replaces thyroid hormone in dogs with hypothyroidism, a common cause of weight gain, lethargy, hair loss and skin disease in middle-aged dogs. Veterinary products are approved for dogs, and the human generic contains the same hormone; dogs need much larger doses per kilogram than people.
What it is used for
Hypothyroidism is one of the commonest hormone disorders in dogs. Once diagnosed by blood tests, treatment is a twice-daily (sometimes once-daily) tablet for life, with the dose adjusted against a blood test a few weeks after starting and then every six to twelve months. Most dogs show a lift in energy within weeks and skin and coat improve over months.
Thyro-Tabs and ThyroKare are FDA-approved veterinary tablets; human levothyroxine is the same hormone and some vets prescribe it, choosing a strength that matches the dog’s weight. Because dogs absorb and clear the hormone faster than people, a dog’s dose is far higher per kilogram, so a human strength that would be a very high dose for a person can be routine for a dog.
Safety points that differ from human use
- Too much hormone causes restlessness, panting, weight loss and a fast heart; the blood test guards against it.
- Give consistently either with or without food, at the same times, since food changes absorption.
- Soy, calcium and iron supplements reduce absorption; separate them by several hours.
- Hypothyroidism is overdiagnosed in dogs because other illnesses lower thyroid levels; the vet may run a full panel before committing to lifelong treatment.
- Tablets (veterinary and human)
- Chewable tablets (veterinary)
- Oral solution (veterinary, some markets)
- Veterinary tablets from 0.1 to 1 mg
- Human tablets from 25 to 300 mcg
Veterinary strengths are labelled in milligrams and human strengths in micrograms; a vet writing for the human product will state the exact strength.
Why the cash price varies
Veterinary levothyroxine is sold through vets and veterinary pharmacies and costs more than the human generic, which is one of the cheapest tablets a pharmacy stocks. For a large dog on a high dose, the human tablet count and strength matter; a vet may prescribe a higher-strength human tablet to keep the count down.
How to pay less
- Ask the vet whether the human generic at a matching strength is suitable, and for a ninety-day prescription.
- Ask the vet to choose a strength that keeps the tablet count low.
- Ask whether levothyroxine is on the pharmacy’s flat-price generic list.
- Upload the prescription to Script Unlock so licensed pharmacies can quote. You pay the pharmacy directly.
Questions for your vet
- Is the diagnosis confirmed with a full thyroid panel?
- Can I use the human generic, and at what exact strength?
- With food or without, and at what times?
- When is the next blood test?
- What signs suggest the dose is too high or too low?
Rules on refills, transfers and controlled substances differ by state; see pharmacy rules by state.
How Script Unlock gets you a cash price for your pet’s levothyroxine prescription
Prices on this site come from pharmacies responding to a real prescription. We do not publish estimated, average or "typical" prices, because none of those would be your price.
- 1You upload your prescription
A photo of your your pet’s levothyroxine prescription prescription is enough. Nothing is sold on the site; you are asking pharmacies to quote.
- 2Licensed pharmacies respond
Pharmacies that Script Unlock has verified see the request and each can reply with its own cash price for your exact drug, strength and quantity.
- 3You choose and pay the pharmacy
You compare the responses, pick a pharmacy, and pay that pharmacy directly when you collect. Script Unlock never takes a patient payment and never sets the price.
Related pet medications
Sources
- FDA Approved Animal Drug Products (Green Book)
- Merck Veterinary Manual
- FDA Orange Book (approved generics and therapeutic equivalence)
Written by the Script Unlock editorial team from the sources above. Not yet reviewed by a veterinarian or veterinary pharmacist. Last checked 2026-10-03. Nothing here replaces your vet\u2019s directions; doses for animals are set by weight and species.
Script Unlock is a marketplace that lets licensed pharmacies quote a cash price on your prescription. It does not prescribe, dispense or sell medication, does not process patient payments, and does not give medical advice. Always follow the instructions of your prescriber and pharmacist and read the medication guide supplied with your medicine.