Hill's Prescription Diet y/d Thyroid Care offers a safe, effective and easy way to manage your cat's overactive thyroid. Each thoughtful bite works to reduce your cat's iodine intake and lower T4 hormone production in as little as three weeks when fed as the sole source of nutrition. It also helps support your cat's kidney, heart and urinary health. And best of all, it comes in a great chicken flavor your kitty can enjoy!