With U.S. healthcare spending approaching 5T(NHEFactSheet2024),and25ofitestimatedtobewasteful(WasteintheUSthehealthcaresystem:estimatedcostsandpotentialforsavings,n.d.),theneedtobetterpredictriskandoptimalpatientcareisevermoreimportant.ThispaperintroducestheLargeMedicalModel(LMM),agenerativepre−trainedtransformer(GPT)designedtoguideandpredictthebroadfacetsofpatientcareandhealthcareadministration.Themodelistrainedonmedicaleventsequencesfromover140Mlongitudinalpatientclaimsrecordswithaspecializedvocabularybuiltfrommedicalterminologysystemsanddemonstratesasuperiorcapabilitytoforecasthealthcarecostsandidentifypotentialriskfactors.Throughexperimentationandvalidation,weshowcasetheLMM′sproficiencyinnotonlyincostandriskpredictions,butalsoindiscerningintricatepatternswithincomplexmedicalconditionsandanabilitytoidentifynovelrelationshipsinpatientcare.TheLMMisabletoimprovebothcostpredictionby14.1modelsandchronicconditionspredictionby1.9modelsinresearchpredictingabroadsetofconditions.TheLMMisasubstantialadvancementinhealthcareanalytics,offeringthepotentialtosignificantlyenhanceriskassessment,costmanagement,andpersonalizedmedicine.