If your employer is in agreement to investigate ill-health retirement they must be satisfied that you are permanently unable to do your job until your Normal Pension Age, and you are not immediately capable of undertaking gainful employment.
Your employer must get the opinion of an Independent Registered Medical Practitioner (IRMP) appointed by them before making the decision.
The IRMP is providing your employer with a medical recommendation in order to help them make a decision about the release of your pension on ill-health retirement grounds.