It would not hurt your non-diabetic dog if it gets DIA-IONX, but I prefer to add the homeopathic to the food rather than the water so the intended recipient will more likely get the whole dose. Initially I give a half dose twice daily on the breakfast and supper food. After improvement I switch to a whole dose once daily on one of the meals. I also like to give PROBIOTICS and OMEGA 3,6,9 to support the body. I would wait to give the well dog the homeopathic if he has no symptoms. The PROBIOTICS and OMEGA 3,6,9 would be a good preventative for the well dog.
Are you giving purified water? It is important to avoid chlorine in the water.
It would be beneficial for both dogs if you can give them a regular moderate exercise schedule. Exercise moves glucose out of the blood stream into the muscles.
Please keep us updated on your progress.