Our Providers
Meet the people
making a difference.
We have been practicing traditional and functional medicine for decades, and are working hard to reinvent and optimize how this medicine is delivered to you.
Providers
Derek Guillory, MD
Derek W. Guillory, MD, our founder and Medical Director, has a passion for functional medicine that was born out of his own personal struggle with health concerns that began before the age of 17. He has an insatiable curiosity for the question most often asked by his patients… “Why am I sick?”
Dr. Guillory became one of the first certified functional medicine practitioners in Texas in 2015. He earned his Bachelor of Science in Education at Baylor University in 1997, graduating Magna Cum Laude. In 2001, he graduated from the University of Texas Southwestern Medical Center in Dallas. He continued his medical training in Emergency Medicine at UT Southwestern Medical Center, graduating in 2004. He has been continuously Board Certified by the American Board of Emergency Medicine since 2005.
“Our mission is to be an instrument of personal healing by effectively treating the underlying causes of disease.
Lucas Tims, ND, FABNO
Dr. Lucas Tims is an integrative oncologist and cofounder of Root Causes Oncology (RCO), the integrative oncology department at Root Causes Medical Clinic in San Antonio, TX. With sixteen years of experience treating and supporting cancer patients, his clinical work rests on a simple but powerful premise: cancer is not bad luck. It’s terrain. His approach centers on terrain theory — the idea that cancer arises from a modifiable internal environment shaped by inflammation, metabolic dysfunction, hormonal imbalance, immune compromise, toxic burden, and chronic infection. As he puts it: the gene loads the gun, terrain pulls the trigger.
This is the central argument of his forthcoming book, Cancer Is Not Bad Luck, which makes the case for reframing cancer away from randomness and toward the biological conditions that allow it to take hold — and, just as importantly, the conditions that can be changed.
Dr. Tims is a graduate of the University of Arkansas (BS, Microbiology) and Sonoran University of Health Sciences (ND, Naturopathic Medicine), and completed his residency in naturopathic oncology at City of Hope. He went on to serve as Medical Director of Integrative Oncology at City of Hope’s Western Regional Medical Center and at the Riordan Clinic. He is a Fellow of the American Board of Naturopathic Oncology (FABNO), a committee member with the Society for Integrative Oncology, and a published researcher and international speaker on integrative approaches to cancer care.
Luke Schulte-Ovalle, Psy. D., NRP
Since 1998, Luke’s career in emergency, prehospital medicine has taken him across the country–from search and rescue and community preparedness with local and regional fire departments to national disaster response with federal agencies and the American Red Cross to the international level with the Defense Institute for Medical Operations and the International Trauma Life Support Program.
His work with EMS and domestic flight crews in the Baltimore/DC Metro area pre- and post-9/11 reinforced his belief in the need for proactive mental healthcare for first responders.
He began studying clinical psychology and human behavior at American Military University and completed his studies at the University of Maryland. Now as a functional psychologist, Luke brings a unique, compassionate insight to his approach to medicine and mental health. His contributions to the care plans of all Root Causes members include a variety of emotional and spiritual support strategies.
Charlotte Widick, APRN, IFMCP
Charlotte’s own health care crisis developed a deep desire to identify the root causes of illness. Each plan is an expression of her goal to create a patient-centered practice with a holistic approach, an empathetic ear, a compassionate heart, and a community vision.
Charlotte has been in health care for almost 40 years. She has a Master of Science of Nursing with certifications in Emergency and Acute Care and has been a nurse practitioner since 1998.
“Functional Medicine determines how and why illness occurs and restores health by addressing the root causes of disease for each individual.
Christal Carter, APRN
Administrative Staff
Scott Lochrie, Head of Practice
Scott Lochrie is a mission-driven healthcare leader dedicated to creating systems that make compassionate, whole-person care accessible. As Head of Practice, he draws on over a decade of experience building physician networks, advancing health-technology solutions, and bringing teams together around people, process, and purpose. Scott believes real change happens when health systems and communities connect—and that the culture of care matters just as much as the care itself. He is energized by Root Causes’ vision of breaking down barriers to health and helping people thrive.