The region is spending £60m more a year than it receives in funding and income.
The figures are in a local NHS review which that found that services in the county were "struggling to deliver consistent, high quality care".
Changes suggested in the report include centralising more services in specialist treatment centres.
An example cited was the bringing together of cardiac services at the Lincolnshire Heart Centre, which opened at Lincoln County Hospital in 2013.
United Lincolnshire Hospitals NHS Trust, which runs the unit, said that "survival rates for heart attacks are now among the best in the country".
Other recommendations in the report include calls for more care to be provided outside hospitals and better communication and better sharing of medical records.
The report also claimed that "more funding would not deal with the challenges in recruiting professionals into key health and care roles, including nurses, GPs, radiologists, paediatricians and other professionals".
Dr Sunil Hindocha, chief clinical officer at Lincolnshire West Clinical Commissioning Groups, said: "What we know is if we carry on doing things in the manner we are, then Lincolnshire's healthcare system is simply not sustainable.
"It is clear we are not getting the best for the population under the current configuration."
The report will form the basis of a public consultation later in the year.
Lincolnshire's health and care system could see a £300m overspend by 2021, according to a new report.