If you mean 'can disciplinary action proceed whilst a person is absent owing to illness', then the answer is a qualified 'yes'. The actions that can proceed would be the gathering of any evidence which it is possible to gather whilst the person is not present. Under some circumstances (e.g. a person still absent owing to illness such as a broken leg), it might be reasonable to ask them to attend a disciplinary hearing. It would not, however, be reasonable to expect a person to attend a disciplinary meeting if their doctor deems them too ill to attend.