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
Originally from Northwest Arkansas, Dr. Lucas Tims is a graduate of the University of Arkansas, where he majored in microbiology. He went on to complete his medical training at Southwest College of Naturopathic Medicine in Tempe, Arizona before moving to Tulsa, Oklahoma for an oncology-focused residency program at City of Hope (formerly known as Cancer Treatment Centers of America). In 2013, he passed additional board exams to become a Fellow of the American Board of Naturopathic Oncology (FABNO).
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.
Haley Kraskovic, FNP-C
I have been blessed to be in nursing for 20 years. I began my career in intensive care, working in a variety of specialties ranging from burn/trauma to pediatrics. I then transitioned into transplant and organ donation and had the privilege of standing by donor families as they made incredibly tough decisions. As I progressed in my career and had my two beautiful children, I began to embrace a more natural and holistic approach to my and my families health.
As I entered Nurse Practitioner Graduate school, my only goal was to practice functional medicine. I was blessed to meet Dr. Guillory and began my career in functional medicine with Root Causes Medicine.
I have spent the last 4 years caring for my patients of all ages helping them heal from their chronic illnesses. I am very passionate in ensuring that my patients and I are working together in a collaborative approach to their health.
I fully believe that my patient’s health journeys should be a positive, empowering experience, rooted in a strong, meaningful partnership with your practitioner and care team.
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.
Leslie Hulick, Patient Care Coordinator
My journey into a holistic lifestyle began out of necessity. I was dealing with a series of unexplained symptoms that left my providers stumped. Refusing to settle, I began a relentless path of self-education. Over time, I started to heal and reclaim my health. One of the most important lessons I’ve learned is that healing isn’t linear. It’s a journey, not a destination—with twists, turns, and new discoveries at every corner.
For over 10 years, I have also been representing young, “better for you” and 1% for the planet brands in the natural food and supplement channel, creating brand awareness and education.
