Does there have to be a diagnosis considered preexisting condition?

In general, yes, there must be a diagnosis or symptoms of a condition present before an insurance policy is issued in order for the condition to be considered a preexisting condition. However, there are some exceptions to this rule, such as for conditions that are considered to be congenital or hereditary, or for conditions that are considered to be chronic and have been present for a long period of time. Ultimately, whether or not a condition is considered a preexisting condition will depend on the specific terms and conditions of the insurance policy.