Dr. Kathleen O’Neil earned her M.D. from Boston University’s School of Medicine.

After training at Massachusetts General Hospital and Brigham and Women’s Hospital, she opened her private clinic to focus on Internal Medicine and personalized healthcare and longevity. 

She is a global expert in the clinical use of advanced regenerative modalities, including peptide therapy, GLP-1s, and exosomes. She specializes in working with elite athletes and coaches, including some of the GOATs of the major league teams.

Dr. O’Neil is a founding board member of both the International Peptide Society and the American Academy of Stem Cell Physicians. From 2017-2018, she served as medical director of Tom Brady’s wellness center, TB12. Her academic appointments include clinical faculty positions at Tufts and Boston University.

Dr. O’Neil has completed multiple fellowships and has earned a series of certifications, which include:

  • A Fellowship at the American Academy of Anti-Aging Medicine (Functional and Regenerative Medicine) - A4M

  • A Fellowship at the American Academy of Age Management Medicine (Traumatic Brain Injury) - AMMG

  • A Fellowship at the American Academy of Anti-Aging and Regenerative Medicine (Stem Cells) - AASCP / A4M

  • A Certification in Applied Positive Psychology from the Flourishing Center at the University of Pennsylvania - CAPP

“The body is a complex yet deeply interconnected system. To understand a patient’s physiology and to get to the root cause of disease, I apply a systems-thinking approach using testing and regenerative therapies."

-Dr. Kathleen O’Neil

Our Patient Testimonials

“I work full-time as a data analyst at a major corporation. This summer, I spent a week in Colorado hiking up peaks of 6,500, 8,600, and 11,300 feet. Every year, I go mountain biking with my son in Arizona. My marriage of 45 years is still as strong and loving as ever. I don't have any prostate issues, arthritis, or aches and pains. I don't take naps. I don't drink coffee. I sleep well, and I have energy all day long. What is my secret? I listen to Dr. Kathleen and follow her advice. She blends years of experience with an understanding of cutting-edge research, to come up with practical solutions that heal and strengthen. Diet, exercise, hydration, supplements, hormones, herbals, electrolytes, biomechanics. Her toolkit is vast and always expanding. But the key is that she listens to each one of us in depth and crafts creative recommendations that fit our unique lives. She understands what we need to build wellness and explains so clearly how it all works. And she does it with wonderful enthusiasm and warmth.”

-Patient, 75-year-old Male

“Dr. O’Neil is one of the few people in the medical profession who truly cares about her patients. Her methods of testing, in addition to her evaluation and explanation of the diagnosis, gives you a level of confidence that you are getting the best treatment possible from the best doctor. She diagnosed my early prostate cancer and helped me to a record recovery. In 2023, she detected a major heart problem. Again, I made a remarkable recovery — so much so the cardiologist is still baffled. Dr. O'Neil is a great person. No doubt.”

-Patient, 64-year-old Male

“Post military service, I struggled with cardiac, endocrine, brain, and nervous system issues from a severe traumatic brain injury. With Dr. O’Neil’s care, I was able to identify and treat each issue. For all things wellness, Dr O’Neil is the only person you need to speak to. She will not let you down.”

-Patient, 34-year-old Female

“I’ve struggled with gut issues for over half of my life. I’ve seen many doctors within the Northeast with the hopes of treating this issue beyond dietary restrictions and colonoscopies. Within a season of working with Dr. O’Neil, I noticed a shift in mental clarity, metabolism, and food tolerance. I highly recommend her for gut and stomach problems.”

-Patient, 27-year-old Female