Leader in Medicine

Rex Mahnensmith


Dr. Rex Mahnensmith, a Primary Care Physician and expert Comprehensive Internist, has been welcomed as “Best in Medicine” of the acclaimed American Health Council. Dr. Mahnensmith has worked in multiple locations in Connecticut including New Haven, Branford, Hamden, Hartford, Waterbury and Southington. He has been working in the healthcare industry for an impressive 40 years and has spent the past 4 years in his current role as Primary Care Internist and Preceptor for PAs and APRNs with DOCS of CT Medical Group.

Dr. Mahnensmith grew up in rural Indiana, where he enjoyed athletics and small-town life.  He suffered a serious life-changing injury when he was 16, requiring major emergency surgery and three weeks of hospital confinement.  However after four months rehabilitation he was able to walk again and he even resumed playing basketball. This extraordinary experience inspired him to help others in a similar way. After college studies at Denison University in Ohio, he matriculated into the prestigious Yale University School of Medicine where he received his MD cum laude in 1977.  During his four years of medical school studies, he was precepted and mentored by metabolic physicians and completed thesis research on metabolic acidosis in humans, yielding two major publications in medical journals. After graduating, he went on to complete a 3-year Internal Medicine Residency Program at Yale, and was asked to serve the following year as Chief Medical Resident and Instructor in Medicine, precepting Interns and Residents and Serving as a Hospital Attending. Following this, he was granted a special 3 year Fellowship in Nephrology, Metabolism and Hypertension also at Yale. His Fellowship years yielded competent expert training in Adult and Pediatric Nephrology care plus Laboratory Research Training in the field of renal responses to metabolic acidosis. He published additional expert articles in research journals and received Life-Time Specialist Certifications by The American Board of Internal Medicine and American Board of Nephrology.

As he transitioned into employment, Dr. Mahnensmith’s first call was to Duke University, serving as Clinician Educator and Assistant Professor of Internal Medicine.  He loved his time at Duke, and he earned a Best Teacher Award and contributed chapters to a major medical and surgical textbook.  He then received a surprise invitation to join a large Private Practice Group, and after long deliberation he decided to serve as a Metabolic Specialist in Private Clinical Practice for two years, but he dearly missed the Educator Role. So, he moved back into Academic Medicine.  From 1987 through 2014, he served in Clinician Educator roles first within Brown University for five years and then at Yale University for 22 years. In these roles, he provided Primary Care, Consultative Nephrology and Metabolic Care, Acute and Chronic Dialysis Care, and he taught Medical Students, Interns, Residents, and Fellows on an ongoing basis and Precepted Numerous Students with their own individual research and Master’s Thesis endeavors.

Dr. Mahnensmith’s Professional Journey has been very positive, he shares, and it has allowed him to gain knowledge and experience in a wide variety of conditions including comprehensive general internal medicine, diabetes, hypertension, metabolic and nutritional conditions, in addition to deep depths and breadths of nephrology and kidney disease management. 

Dr. Mahnensmith retired with Honors from Yale School of Medicine in 2014, but he has continued providing care to many many individuals. 

Presently, he loves serving folks with DOCS of CT Medical Group. This Practicing Group is proud to offer the best care and support possible to anyone who visits their  clinics. They specialize in providing both primary and follow up care to anyone, of any age, that requires medical care. The services provided by DOCS of CT include, but are not limited to primary care, urgent care, comprehensive general internal medicine care and family care as well as allergy testing, ongoing allergy care, and comprehensive pulmonary care.

Rex Mahnensmith, MD provides exceptional and personalized primary care with DOCS Medical Group at DOCS Care Center locations in Southington and Waterbury. Dr. Rex aims to connect with each person according to their needs and concerns and aims to deliver excellent care with caring and carefulness.

Practicing since 1984, Dr. Rex has specialized in Nephrology Care wherein he provided deep and broad expert care to patients with acute and chronic kidney diseases of all types, including the comprehensive care of folks requiring maintenance dialysis for life. He was recognized as a knowledge and practice leader throughout these years and served as Advisor and Medical Director for Dialysis Care in multiple Dialysis Care Centers. National Dialysis Providers recruited him to serve as Regional Advisors for Quality Assurance and Quality Improvement within their centers and this led him to National Medicare Advisory endeavors as well. He was viewed as an outstanding Clinician Educator at Yale University since 1992, and he continues to be sought for Expert Consultations.

Dr. Mahnensmith is very pleased to serve in three of the DOCS Clinics four days per-week, every week, where he sees individuals and families through appointments but is always on hand to give any urgent or walk-in care as required. Alongside these responsibilities, Dr. Mahnensmith also provides care to those who are triaged from hospitals and nursing homes, connecting with individuals to provide collaborative follow up care, metabolic care, allergy evaluations and care, asthma care, and ongoing preventative care so their conditions do not worsen.

Throughout his wide-ranging career, Dr. Mahnensmith has had many successes. For example, he received multiple Teacher of the Year awards from both Brown Medical School and Yale Medical School, with the Yale award being specifically for internal medicine. He received special recognitions in successive years as Model Physician at Brown Medical School. The Physician’s Associate Master’s Program at Yale also recognized Dr. Mahnensmith as “Best Teacher” on two occasions.  Dr. Mahnensmith also served as Divisional and Regional Medical Director with both the Gambro and DaVita National Dialysis Corporations, and he provided consultant services between Gambro Dialysis Corporation and the National Medicare Oversight Board for 3 years.  During his later years at Yale University, Dr. Mahnensmith served on the Chairman’s Advisory Board for Best Practices in the Internal Medicine Department and rose to Full Professor of Medicine rank with tenure and ultimately Professor Emeritus designation. In addition, he served as Yale Nephrology Fellowship Program Director and Clinical Director of Nephrology for several years. Alongside these responsibilities, Dr. Mahnensmith served for over 15 years as Medical Director at The New Haven Dialysis and Branford Dialysis Clinics. Supplementing these achievements, he received the Bernicker Award from Yale as the individual who best modeled the Principles of Maimonides’ Prayer and the Oath of Hippocrates. In a subsequent year, he received the Kushlan Award as Best Intern within Yale’s Program of Internal Medicine.  

Finally, in 2017 and 2018, Dr. Mahnensmith received The Continental Who’s Who Pinnacle Achievement Award. And, in full recognition, Dr. Mahnensmith recently was named recipient of The Distinguished Achievement Award by the American Board of Nephrology in Philadelphia and special Designation as Grand Master of the American College of Nephrology in recognition for Excellence in Nephrology by the Director and Board Members, and Board of Governors of the American Board of Nephrology. 

He credits his vast success to caring mentors in leadership positions who provided encouragement and affirmation to him throughout his professional journey as well as the continual loving support from his wife and family.

To share his knowledge, Dr. Mahnensmith is a member of the American Society of Nephrology, the American Telemedicine Association and the American Medical Association and continues to precept Nurse Practitioners in Training, Physician Associate students, and newly-licensed PAs and APRNs and younger Physicians. 

In his personal life, Dr. Mahnensmith loves to spend time with his wife, his dogs, his family of children and grandchildren, taking walks, gardening, enjoying local wildlife, and serving the needs of people where he lives.  He is passionate about supporting charities including Compassion International, various Missions of The Christ Community Church of Collinsville and local Food Banks.

In the next five years, he wants to continue providing optimal, connected care to his patients, conferring care with carefulness which is his Calling as a Caring-Servant-Physician.  He has stated that serving others as Physician Is A Calling to which he has always aimed to be Faithful.  

Primary Care Physician at DOCS of CT Medical Group Primary Care

  • The DOCS of CT are the leading provider of general and specialty medical care in Connecticut.
  • Urgent care centers are open 365 days a year, with extended weekend hours, for medical needs that require immediate attention.
  • The DOCS of CT urgent care facilities also offer medical testing, imaging & x-ray services, blood work, primary care, and more. DOCS Medical Group is also proud to offer specialty services at various locations.

Top Internist and Nephrology Specialist, Dr. Rex Mahnensmith, MD is Meritoriously Named a “Patient Preferred Physician” Representing the State of Connecticut for 2021!

  • For his dedication to medicine and for achieving excellence in patient care, Patient Preferred Physicians and Practitioners proudly named Dr. Rex L. Mahnensmith, MD a 2021“Patient Preferred Physician” representing the state of Connecticut.