Yes, if you were to get admitted to a non panel hospital, the medical report is not submitted directly to your insurer.

This means that the insurer has no idea as to why you were admitted for apart from the bill that you had submitted.

You will also need to get the discharge summary, itemized billing, police report (if any), medical or investigative reports such as blood test results (if any) for the claim.

That is why it is easier to get admitted to a panel hospital.

Also if you want to claim from multiple insurer (up to the maximum of the bill), you will need to CTC the supporting documents.

For the variance bill that is not paid by the first insurer, the bill submitted to the second insurer must be original.