Is there any other way I can use "diagnose"? Like "diagnose to something"? Or should I always use "diagnose with"?
Yes, there are other ways you can use the word "diagnose", and it does not always have to be used as "diagnosed with". However, "diagnosed with" is a common use of the word when using it to describe what the result is from the process of "diagnosing" someone, because "diagnose" means to recognize or detect a condition of something. You can use "diagnose to", however, this is a little less common. Ex: The child was diagnosed to better understand his mental disabilities. Ex: The engineer diagnosed the problem with the computer. Ex: The doctors haven't diagnosed the disease.