Depends on the type of health organization:

provider organizations like hospitals may have a strong geographic approach as well as specialising by disease or service. They also may specialize according to the framework of the health care system for public paid services or private services.

payer organizations may use provider types they have contracts with to segment their view on services - hospitals , pharmacies, doctors in single practices. Or on the type of services- pharmaceuticals , medical interventions (fee for service), inpatient procedures, long time care and services for chronic conditions (bundle payment , capitation or HMO type reimbursement of services).

decision makers may use service levels - primary, secondary, tertiary care. Or they may take the preferences of patients to shape the service provision landscape - self relating/self managing patients//less empowered patients// marginalized groups - needing choice or increasingly dependent on guidance, regulation and actively visiting and inviting service organization.

So different types of health organizations (public, private, for or not for profit, providng services or organicing the health care system) have different types of "consumers/customers/clients/patients" . so they will end up with different characteristics for segmentation. These characteristics should  be documented/expressed in the vision/mission statement of the individual organization or in the regulatory framework for the more general defined type of organization. 

I think Age Group is the major one. Second one type is based on organs or decease, family

Identify the intended users based on epidemiology (who is affected?), demographics, behavior, culture, and attitude. This is known as segmentation

https://www.google.co.in/url?sa=t&source=web&rct=j&url=http://health.gov/communication/literacy/quickguide/healthinfo.htm&ved=0ahUKEwilmfLl9LDJAhWWj44KHdgRBMQ4PBAWCCAwAg&usg=AFQjCNHpwTmvQn2VXmNoQjoR_cPfBeneHw&sig2=mWvI_kWdbTh7Un_rL4gfoQ