As a member of a statutory health insurance, you can apply for these benefits every 3 years. You should submit your spa application to the health insurance company at least 3 months before the planned spa treatment. The application should be completed by your trusted/family physician.
In the event of approval, this will not have any negative consequences for his budget! If the application is rejected, you can and should appeal against it in writing – ideally with the support of your doctor.