for further detail (in German) follow this Link
In Germany some medical services do exist which are not covered by the insurance (Krankenkassen). These are not part of the accepted catalog of services. They comprise a wide field beginning with lab tests and ending with expensive imaging like MRI.
Here is our statement and opinion: Every investigation, we find necessary for diagnosis will not be charged to you. If e.g. an unusual lab test is required it will either be performed by us or you will be referred. In case of dispute with the insurance we and not you would have to answer.
However, we will NOT suggest any "IGel" to you since we regard most of them as useless.
Naturally, you can always request and obtain any service or lab test not necessarily required if you wish. For example, long-time blood sugar test or an ergometry without having signs of a cardiac disease. Should this result in laboratory cost you would receive a bill directly from the lab. We will not and do not wish to earn money on this.