This question can be answered only with reference to the industrial establishment in which the employee is employed and its leave regulations. As far as I know generally there is no such category of " medical leave" in the Labour Laws. But it may find its place in the leave provisions of any industrial establishment as an additional leave benefit as in the case of unearned leave on medical grounds available to Central and State Govt. employees.
However, in the absence of any sufficient leave in his/her credit and a long spell of leave is required on genuine medical reasons, an employee can apply for leave on loss of wages on medical grounds supported by a certificate issued by any registered medical practioner in order to avoid break of continuity of service.
In case the employer has any doubt regarding the authenticity of the medical certificate furnished by the employee, he can refer the employee for a Medical Board's examination.