For emergencies, immediately call 911.
For urgent matters during business hours, please call our office at (208) 385-7711.
For emergencies, immediately call 911.
For urgent matters during business hours, please call our office at (208) 385-7711.
FMI is here to help you. Whether you need assistance finding a provider, have questions about your bill, or need to get in contact with your provider, it is our intent to efficiently connect you with the appropriate person who can promptly answer your questions.
Please do not send direct emails containing medical information. Emails that are NOT sent through the Patient Portal are not considered HIPAA compliant. We will respond to all emails with a phone call.
Please do not contact providers via text message or social media messaging. They will not be able to respond on those platforms.
Contact our offices at (208) 385-7711. Please note that our menu options have changed.
To talk with the Boise office, press 1.
To talk with the Meridian office, press 2.
To talk with the Eagle office, press 3.
To talk with the Sandpoint office, please press 4.
To reach a specific department or the medical assistant for a particular provider, please call our office and enter the extension at any time.
Eagle Front Desk — 200
Meridian Front Desk — 312, 320, 328, 338, 346
Boise Front Desk — 400
Sandpoint Front Desk — 500
Eagle Supplement Counter — 201
Meridian Supplement Counter — 302, 327
Boise Supplement Counter — 406
Wellness Department — 350
Marketing Department — 314
Women’s Health Department — 319
Pediatric Department — 306
Billing Department — 326, 331
Phlebotomy — 325
Dr. Mark Holthouse’s MA — 335
Dr. Mario Brus’s MA — 348
Dr. Jennifer Hudson’s MA — 318
Dr. David Musnick’s MA — 202
Amber Warren’s MA — 403
Karen Callagy’s MA — 403
Amy Ray’s MA — 403
Jessica Bennett’s MA — 334
Michael Sermon’s MA — 340
Jessica Santos’s MA — 336
Heidi Arens’s MA — 330
Stefanie Magee’s MA — 348
Olivia Mangeac’s MA — 347
Christina Rust’s MA — 501
Janessa Tenney’s MA — 309
Nadia Kravchuk’s MA — 347
Aaron Dykstra’s MA — 203
Stephanie Ritari’s MA — 311
In the event you call and reach our voicemail, know that we will return your call as quickly as possible. When you leave your message, please state the patient’s full name, birth date and reason for your call in the recording.
We have an established a Patient Portal that you may use to communicate with FMI:
The Secure Messages Center within the Patient Portal provides a secure, encrypted alternative to email for electronic communications with your medical provider. Your secure messages can be read only by select Functional Medicine of Idaho staff members.
*Please note: The Patient Portal is not to be used as an alternative to an appointment.
How to send a secure message in your Patient Portal
If you need a prescription refill, please call your pharmacy and have them fax us a prescription refill request form.
Fax number: (208) 385-0346
For after office hours patient care, please call our office at (208) 385-7711 to be directed to our on-call service, who will then get in touch with your FMI provider if necessary.
For non-medical questions regarding becoming a new patient, please send us an email through the form below. Please do not include any personal medical information.
If you are wanting to inquire about becoming a patient, please visit our New Patient Inquiry page by clicking here.
Josiah Smith graduated with his Bachelor of Science degree in Physician Assistant Studies from Drexel University in 1998. He continued his education and received his Master of Physician Assistant Studies in 2007. He served as a medical officer with the Army National Guard and earned the rank of Captain. He started his career in Family Practice and moved onto Emergency Medicine and Urgent Care. When he experienced overwhelming life stressors ten years ago, he sought out conventional medical care and all that was offered were several “pills.” Not satisfied that this would fix the “root” cause of his symptoms, Josiah found a Functional Medical provider that transformed his wellbeing through a lifestyle and root cause resolution approach. Impressed with his health transformation, he started his own pursuit of being trained in Functional Medicine.
Josiah opened his own functional medicine consulting practice in Las Vegas with several health coaches. His professional pursuits continued into learning how to optimize the body’s healing potential via other therapeutic interventions. He uses regenerative medicine for aesthetics, sexual wellness, repair and recovery of the body. These include peptide therapy, hormone optimization, IV infusions, Acoustic Wave Therapy, and other cellular interventions to enhance vitality and longevity.
In his personal time he enjoys international traveling and exploring cultures, history, and cuisine with his wife and four teenagers. Josiah also enjoys hiking and skiing.
Kristin is a Certified Nurse Midwife. She received a bachelor’s of science in nursing from California State University San Bernardino. After working as a registered nurse in transplant, oncology, and palliative care Kristin switched her focus to gynecology, labor, and birth. Recognizing the need to emphasize health, wellness, and prevention in our culture, she saw an opportunity to impact the health of women and their families through education focused, more personalized, family centered care. Thus, Kristin pursued a graduate degree in nurse midwifery at New York University and graduated with honors in 2014. She has practiced as a nurse midwife in the Treasure Valley since 2015.
Throughout her years of practice Kristin has always strived to provide an inclusive and holistic approach to healthcare. She aspires to meet each woman where they are and collaborate with them on their health journey. She has seen the profound difference in treating a symptom vs treating the cause while supporting the body. The desire to support the innate healing and protective qualities of the body through evidenced based care led to her discovery of functional medicine. In late 2020 she began her training through the Institute for Functional Medicine which she completed in the winter of 2022. At Functional Medicine of Idaho alongside the community of practitioners, nutritionists, nurses, and health coaches Kristin has the opportunity to provide a personalized and integrative women’s health experience focused on individualized wellness.
Kristin feels deeply connected to nature. When she’s not in the mountains camping, hiking, kayaking, or fishing you can find her tending her garden beds or on her yoga mat. Her favorite season is winter, preferably one with lots of snow, and her happy place is on her skis with her husband and daughter.
Allyson Howarth is a board-certified Family Nurse Practitioner and Women’s Health Nurse Practitioner. She offers functional primary care and women’s health care. Allyson's heart for women's health began as a labor and delivery nurse in 2011 out of a strong desire to provide a safe place for women to heal physically, emotionally and spiritually.
Allyson discovered Functional Medicine through her own personal struggle with autoimmune disease. When traditional medicine didn’t have a solution for her poor health, she wholeheartedly embraced functional medicine in her quest for healing. She is passionate about helping her patients find healing and is excited to be able to implement functional medicine principles with conventional healthcare.
Allyson is working towards her certification with the institute of Functional Medicine. Allyson earned her Bachelor of Science in Nursing from Oregon Health Science University, a Master of Art in Human Services with an emphasis in Health and Wellness from Liberty University, and both of her Master of Science in Nursing and Doctorate of Nursing Practice from Frontier Nursing University.
Outside of work, Allyson’s favorite activity is spending time with her family. She also enjoys reading, researching, traveling, biking on the Green Belt, and hiking with her husband.
Gavin Guard believes that the average doctor visit is not giving patients the time and support they deserve. Gavin graduated summa cum laude from Whitman College with a bachelor’s in biochemistry before completing graduate medical school training at the University of Colorado. His main clinical focuses include gastrointestinal disorders, thyroid and hormone health, as well as metabolic disease like diabetes, high cholesterol, and heart disease. Aside from patient care, Gavin is also publishing medical literature in the functional medicine field. He wakes up every morning to help patients find lasting solutions to their health so that they can experience hope and feel restored. When not in the clinic or reading papers, you can find him spending time with his wife and two young girls or pumping iron in the weight room.
- Digestive concerns (IBS, SIBO, reflux, bloating, diarrhea, constipation, IBD)
- Longevity and metabolic health (heart health, blood pressure, blood sugar, cholesterol, weight loss)
- Mold illness and toxicity
- Thyroid health
- Hormones (testosterone, menopause, female hormones)
- Brain fog, fatigue
Jennifer Paulson joins FMI after 8 years of owning her private practice in Bend, Oregon. She is dually board-certified as a Family Nurse Practitioner and Advanced Practice Holistic Nurse. She earned her Doctor of Nursing Practice degree from University of Arizona and completed her graduate studies in Nursing at Concordia University in Wisconsin.
Jennifer discovered early in her primary care role as a nurse practitioner that the band-aid approach used in medical settings was not the way she wanted to practice. She knew from her personal healing journey with autoimmune disease and recovering her children from neurodevelopmental disorders she needed a different model to provide care to her patients. She earned her certification with the Institute of Functional Medicine in 2017. Her practice style is unique and she truly meets each patient where they are on their wellness journey while holding space for learning and growing. She enjoys caring for patients of all ages.
Jennifer also holds certifications and advanced studies in mind-body-medicine such as Yoga, Reiki, HeartMath™, Ayurveda, Holistic Pelvic Care™, and lifestyle genomics. Jennifer is an educator at heart and has held faculty positions with Georgetown University and currently teaches Doctor of Nutrition students at University of Western States.
In her time outside of work, Jennifer loves gardening, baking, fishing and spending time with her growing family-husband, children, grandchildren, cats, and dogs.
Christa Inzer Castillo is a board certified Physician Assistant, with 14 years of experience in family practice, who offers primary and acute care for adults and children. She loves the opportunity to get to know entire families and develop relationships with her patients. While trained in western medicine she has long infused a whole person and natural approaches to achieve best patient outcomes.
Personal experience, specifically a mother who has responded poorly to the traditional western medical approach, but used whole body approaches to find answers inspired Christa to begin the process of understanding root cause medicine. The desire to help answer “why” is this going on in the body and “how” to help the body heal has become a passion. The process of teasing out each person’s unique puzzle is fascinating and rewarding, especially when you start to see health restored.
Christa grew up in the Treasure Valley, graduated from Meridian High School, earned her Bachelor of Science in Biology from the College of Idaho. In 2008 she earned her Master of Science in Physician Assistant Studies and Masters of Public Health from Touro University in Vallejo, California.
Outside of the clinic, Christa enjoys spending time with her husband and 3 children. You can find them outside working on numerous projects with chickens, goats, rabbits, dogs, cats, and gardening, or hiking and exploring the great state of Idaho. She also loves to serve in her church and squeeze in a swim.
Stephanie Ritari is a board-certified Physician Assistant who offers primary care for adults at the Functional Medicine of Idaho Meridian Wellness Center. She specializes in Internal Medicine and has spent the majority of her career in the field of cardiovascular disorders.
Stephanie has more than 15 years experience as a Physician Assistant in a variety of medical areas, including cardiology and electrophysiology. Holistic practices have long been a part of Stephanie’s lifestyle, with a particular focus on clean living and nutrition. She has embedded functional principles into her conventional medicine practice throughout her career. After watching family members struggle to find answers for their chronic illnesses, Stephanie became more interested in finding ways to take a root cause approach in her own practice. Wanting to provide a proactive, comprehensive, and preventative scope of care for her patients, Stephanie began studying functional medicine. In 2021, she joined Functional Medicine of Idaho, where she is able to provide evidence based, root cause medicine.
Stephanie earned her Bachelor's of Science in Exercise Physiology from the University of Montana and her masters in Physician Assistant Studies from Rocky Mountain College. She is currently working towards her certification with The Institute for Functional Medicine.
In her spare time, Stephanie enjoys spending time with her husband, son, and dog doing outdoor activities including biking, hiking, and skiing. She also loves interior design and traveling, and is hoping to start her own garden in the near future.
David Musnick is a board-certified medical doctor who offers in-person and telemedicine care from the Functional Medicine of Idaho Eagle clinic. Dr. Musnick offers Functional Medicine, Sports Medicine, Functional Immunology, and Primary Care for adults and teenagers. He specializes in sports medicine, internal medicine, frequency specific microcurrent (FSM), scars, homeopathy, prolotherapy, and low-level laser treatments.
Dr. Musnick is interested in getting to the root of underlying causes and factors that affect healing, including diet, sleep, exercise, stress, mood, GI health, brain region health, toxins, mold, hormones, infections, and electromagnetic fields (EMF). He is excellent at Orthopedic diagnosis trying to determine which tissues are causing pain, what the issue with the tissue is and what is going on in the pain processing system. He has developed a unique program to heal the brain after Concussion that is based on what actually goes on in the brain after head injury. His program integrates: diet, supplements, sleep, exercise and microcurrent and brain training to heal the brain after concussion. He also applies this to other brain based disorders including cognitive impairment and dementia. He has a special interest in autoimmune disorders and has studied Functional Immunology. He is one of the top 10 clinicians in the world with Frequency Specific Microcurrent and he teaches at Microcurrent meetings. He is also very experienced in Prolotherapy regenerative injections to build more ligament to stabilize a joint or area of the spine.
In medical school, Dr. Musnick spent a year studying nutrition. He has always been interested in the complex interrelationships of different systems of the body. Taking on challenges in the past, he created new treatment programs to heal the brain after concussion, treat chronic pain, arthritis, and tough SIBO and IBS cases. Dr. Musnick wants to help his patients achieve the highest level of health, vitality and function.
After his internal medicine residency in Seattle, Dr. Musnick completed a fellowship in sports medicine where he became interested in helping patients get back to optimal musculoskeletal health and eventually back to their favorite activities. He quickly learned that many areas of the body were interrelated and started learning more about nutrition, supplements, and other facets of functional medicine. Dr. Musnick has more than 24 years of experience in Functional Medicine and achieved a very high level of both experience and expertise with many health conditions. He is also the author of the book, Conditioning for Outdoor Fitness, and helped in writing textbook chapters on arthritis and concussions.
Dr. Musnick received his Doctorate of Medicine from the University of California, San Francisco. He is certified through the Institute for Functional Medicine as an IFMCP. He also studied in the French school of Homeopathy. He is uniquely rare in that he teaches Frequency Specific Microcurrent (FSM) and how to integrate it with functional medicine.
In his spare time, Dr. Musnick enjoys hiking, nature photography, cooking healthy food, mountain biking, and skiing.
Aaron Dykstra is a board certified Family Nurse Practitioner with a Doctor of Nursing Practice degree. He offers pediatric primary care, including well-child checks and acute visits, in the Pediatric Department of the Functional Medicine of Idaho Meridian Wellness Center.
Functional and alternative therapies were a part of Aaron’s life from a young age, and he has implemented these principles into his conventional medicine practice throughout his career. Aaron has more than 8 years of experience in a variety of medical disciplines, including pediatrics, obstetrics, mental health, and nutrition. He has practiced in rural health clinics in California and Oregon. For the last 5 years, Aaron has had a passion for working with children and implementing positive change through the family unit. Aaron joined the Functional Medicine of Idaho Pediatric Team in 2021. His enthusiasm for educating children and parents about living a healthy lifestyle allows him to provide preventative and acute care for infants, children, and adolescents.
Aaron obtained his Bachelor of Science in Nursing at Brigham Young University. He earned both his Master’s of Science in Nursing and Doctor of Nursing Practice through the University of Arizona. He has obtained a Family Herbalist and Family Nutritionist certifications through The School of Natural Healing by Dr. Christopher. He is currently working towards his certification with The Institute for Functional Medicine.
Outside of work, you will find Aaron spending time with his wife and 5 kids, mountain biking, running, or camping in the backyard. Aaron is a big fan of Master Chef and enjoys cooking.
Nadia Kravchuk is a board certified Family Nurse Practitioner with a Doctor of Nursing Practice degree. She offers functional pediatric primary care, including well-child checks and acute visits, in the Pediatric Department of the Functional Medicine of Idaho Meridian Wellness Center.
Nadia and her family immigrated to the United States in 1989 where they first settled in Oregon and then moved to Idaho in 2001. Complementary medicine practices were embedded into her lifestyle at a young age, and she has implemented these principles into her conventional medicine practice throughout her career. She has more than 15 years experience in a variety of medical environments, including emergency room, intensive care unit, pediatrics, obstetrics and gynecology, family practice, and aesthetics.
Nadia joined Functional Medicine of Idaho so that she can combine functional principles with the foundations of conventional medicine to address the underlying causes of disease and promote optimal wellness. As an avid gardener, beekeeper, and sustainable living enthusiast, she understands the importance and role of optimizing nutrition, sleep, physical, spiritual, and emotional well-being. She has a passion for pediatric functional medicine and understands that early recognition and interventions can correct imbalances, prevent chronic illness, and improve overall outcomes for children.
Nadia obtained her Bachelor of Science in Nursing at Northwest Nazarene University. She earned both her Master’s of Science in Nursing and Doctor of Nursing Practice through Frontier Nursing University. In 2017, she was the recipient of the HCA Excellence in Nursing Award. She is currently working towards her certification with The Institute for Functional Medicine.
Outside of work, you will find Nadia working on her urban homestead, hiking, foraging, camping, snowboarding, and spending time with her husband and her dog, Wolfy. She is also fluent in both English and Russian.