No, a patient cannot dictate to any doctor as to what to write and doctors have to follow their protocol. Clause 7.7 of the Indian Medical Council Professional Conduct, Etiquette and Ethics Regulations, 2002, states that the name of the doctor will be deleted from the register of Medical Council if he/she is found to have signed, or given under his name, any certificate, report, etc., which is false or misleading. The provisions of Clause 7.7 are reproduced hereunder: 

“7.7 Signing Professional Certificates, Reports and other Documents: Registered medical practitioners are in certain cases bound by law to give, or may from time to time be called upon or requested to give certificates, notification, reports and other documents of similar character signed by them in their professional capacity for subsequent use in the courts or for administrative purposes etc. Such documents, among others, include the ones given at Appendix –4. Any registered practitioner who is shown to have signed or given under his name and authority any such certificate, notification, report or document of a similar character which is untrue, misleading or improper, is liable to have his name deleted from the Register.” 

Therefore, if a doctor writes what is dictated by the patient without following the proper protocol, and it is found to be untrue or misleading, then the Medical Council of India or the respective state medical council will delete his name from the register of the respective medical council in which he/she is registered.