If a cat with hyperthyroidism is currently controlled on medication for treatment, then switching to our fresh meals would be suitable! Medications can control the disease without the use of a prescription diet.If they are currently being fed Hill's Thyroid Care y/d or this has been prescribed by your vet, then a switch to our fresh meals would not be appropriate without chatting to your vet first. Thyroid Care y/d is an iodine-restricted diet that is unique among commercial diets and intended only for hyperthyroid cats. We work in line with vet recommendations regarding your cat's Hyperthyroidism, however if you would like additional support from our in-house vet team please send an email to meow@katkin.com