This code system http://hl7.org/fhir/flag-category defines the following codes:

CodeDisplayDefinition
dietDietFlags related to the subject's dietary needs.
drugDrugFlags related to the patient's medications.
labLabFlags related to performing laboratory tests and related processes (e.g. phlebotomy).
adminAdministrativeFlags related to administrative and financial processes.
contactSubject contactFlags related to coming into contact with the patient.