Thyforon is a thiamazole (methimazole) tablet manufactured by Dechra for the treatment of feline hyperthyroidism. It is one of the most affordable long-term treatment options for this common condition in older cats. Thiamazole works by blocking thyroid hormone production.

Price Comparison

Thyforon tablets (per month supply):

  • From your vet: £12–£28 per month
  • Online pharmacies (with prescription): £7–£18 per month
  • Generic thiamazole: £5–£12 per month from online pharmacies

Thyforon is already one of the cheaper hyperthyroid treatments, and online pharmacies offer further savings of 35–55%.

What Does Thyforon Treat?

Thyforon is licensed for the stabilisation of hyperthyroidism in cats prior to surgical thyroidectomy and for the long-term management of feline hyperthyroidism. It is the same active ingredient (thiamazole/methimazole) that has been used for decades in both human and veterinary medicine.

Species and Forms

  • Cats only: Sugar-coated tablets in 2.5mg and 5mg sizes
  • Dosing: Typically 2.5mg twice daily initially, adjusted based on blood test results
  • Can be given with or without food

Side Effects

  • Vomiting, reduced appetite, and lethargy — most common in the first 2–3 weeks
  • Facial itching and self-excoriation — stop medication and contact your vet immediately if this occurs
  • Blood disorders (agranulocytosis, thrombocytopenia) — rare but potentially life-threatening; requires monitoring
  • Liver toxicity — occasional; monitor liver values on blood tests
  • Blood tests every 3–6 months are essential for safe long-term use

Thyforon vs Vidalta

  • Dosing frequency: Thyforon is twice daily; Vidalta is once daily
  • Cost: Thyforon is cheaper (£7–£18/month online vs £15–£28 for Vidalta)
  • Compliance: Once-daily Vidalta is easier for many owners
  • Dose adjustment: Thyforon is easier to fine-tune in small increments

Prescription Requirements

Thyforon is POM-V. Obtain a written prescription to buy from online pharmacies.

How to Save

  • Written prescription: Save 35–55% by buying from online pharmacies
  • Generic thiamazole: Even cheaper than branded Thyforon
  • Compare pharmacy prices: Use VetCost to compare across pharmacies
  • Consider radioactive iodine: A one-off cure at £2,000–£3,500 may be cheaper than years of daily medication

Last updated: March 2026. Sources: VMD product datasheet, CMA provisional decision (October 2025), VetCost pharmacy data.