Depends. If your cat has health issues now, you may see a dramatic change within a couple of weeks, but it depends on several factors - what the problem is, how long your cat has had it, what sort of treatment you have been doing up to this point, etc. If you read the comments some of our clients have sent in, you'll read about some who have seen results in days. But on average, you should see noticeable results within one month.
If your cat is young with no current health issues, you may not directly notice a change now. The major benefit of giving Dr. Jones' Ultimate Feline Health Formula to a young, healthy cat is PREVENTION. This is something I always advise my clients: if you can do anything to help prevent disease in your cat in the long run, do it - with better food, fewer vaccines, and supplements. If your cat develops a serious disease such as cancer, the cost to you and your cat, both financially and emotionally, will be more than the cost of a daily supplement now, by far. Just ask anyone who has a cat now with a serious health condition, or anyone (including myself) who lost a cat before his time.