The following is my approach to feline diabetes. I would give DIA-IONX along with insulin. DIA-IONX was designed to help with the symptoms of diabetes and to stimulate the body to heal. Healing takes time and so you need to monitor blood glucose levels to determine if it is appropriate to adjust your therapy. You may find your cat needs less insulin. Initially I would give 10 drops of DIA-IONX on the breakfast and supper food.
In the cat there are factors that help them to respond well to therapy if you do not feed any dry food and give a diet that is less than 2% carbohydrates. Dry food stresses out the pancreas.
For both cats it is important to give filtered water so you can avoid chlorine. I would also give PROBIOTICS and OMEGA 3,6,9 to both cats.
For thyroid issues I use DIA-IONX. I would give 10 drops on the breakfast and supper food. I would choose a grain-free food preferably using fish or turkey as the protein source. I would not stop conventional medications or reduce them without finding improvements in the body and then discussing it with your veterinarian. Homeopathics stimulate the body to heal and is not a drug replacement.