410. Don't simply tell the doctors. The ASR's on this topic seem pointless too. Who's going to ruin the day by dropping that hot potato at the next meeting? Call Crew Control, make sure they mark you down as Fatigued. Be specific: not sick, but fatigued and ensure they give the correct code.
The roster records must be kept. If the fatigue level is as high as it is claimed to be then the records will show this and no-one will have the inclination to tamper with the records retrospectively. They are kept by far too many people.
Be smart - Telling people things is a waste of breath around these parts. Its forgotten the moment you are out of sight. Everything must go on record.