FDN Practitioner (Functional Diagnostic Nutrition)

A holistic approach to health that identifies and addresses the root causes of chronic health issues through functional lab testing, lifestyle changes, and personalized protocols.


FDN Practitioner, or Functional Diagnostic Nutrition Practitioner, is a health professional who utilizes a comprehensive, holistic approach to identify and address the underlying causes of chronic health complaints. By combining functional lab testing, thorough client intake processes, and personalized lifestyle and dietary protocols, FDN Practitioners aim to restore balance to the body's systems and optimize overall health and well-being. This approach focuses on the individual's unique biochemistry and health history, rather than merely treating symptoms, to create sustainable, long-term health solutions.

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Functional Diagnostic Nutrition (FDN) was founded by Reed Davis, a clinical nutritionist and health educator, in 2008. Davis developed the FDN methodology after years of working with clients and recognizing the limitations of conventional approaches in addressing chronic health issues. Drawing from his background in nutrition, functional medicine, and health coaching, he created a systematic approach that combines functional lab testing, lifestyle modifications, and personalized protocols to help clients achieve optimal health. Since its inception, the FDN methodology has gained recognition and has been adopted by health professionals worldwide, leading to the establishment of the FDN Practitioner certification program.


  1. Root Cause Resolution FDN Practitioners focus on identifying and addressing the underlying causes of health issues, rather than merely treating symptoms, leading to more effective and long-lasting results.
  2. Personalized Approach By considering each client's unique biochemistry, health history, and lifestyle factors, FDN Practitioners develop customized protocols tailored to the individual's specific needs.
  3. Comprehensive Assessment FDN Practitioners utilize functional lab testing and thorough client intake processes to gain a comprehensive understanding of the client's health status, enabling targeted interventions.
  4. Emphasis on Education FDN Practitioners prioritize client education, empowering individuals with the knowledge and tools needed to take control of their health and maintain long-term well-being.
  5. Holistic Approach By addressing the interconnectedness of various body systems and considering factors such as nutrition, lifestyle, and stress, FDN Practitioners promote a holistic approach to health optimization.
  6. Non-Invasive Interventions FDN Practitioners prioritize non-invasive interventions, such as dietary modifications, lifestyle changes, and targeted supplementation, minimizing the reliance on medication when possible.
  7. Collaborative Partnership FDN Practitioners work closely with clients, fostering a supportive and collaborative relationship that encourages active participation and commitment to the healing process.

How It Works

FDN Practitioners use functional lab testing and in-depth health assessments to identify underlying physiological imbalances contributing to health issues. They analyze hormone, immune, digestion, detoxification, energy, and nervous system function to develop personalized health restoration programs. FDN Practitioners focus on the root causes of dysfunction rather than simply treating symptoms. They educate clients about diet, rest, exercise, stress reduction, and supplementation to support the body's innate healing processes, helping them achieve sustainable wellness.


Working with an FDN Practitioner requires a commitment to making diet and lifestyle changes. While FDN can be highly effective, it may take time to see results as the body heals. Functional lab testing can be expensive and may not be fully covered by insurance. Clients should ensure they feel aligned with their practitioner's approach, as the client-practitioner relationship is key to success. As with any health intervention, individual results may vary. Those with complex health conditions should consult their primary care provider before beginning a program.

How Much It Costs

The cost of working with an FDN Practitioner can vary depending on factors such as the practitioner's experience, location, and the specific lab tests and protocols recommended. Initial consultations typically range from $200 to $400, with follow-up sessions costing $100 to $200 each. Functional lab tests can cost anywhere from $200 to over $1,000, depending on complexity. Some practitioners offer packages bundling consultations and testing, ranging from $1,000 to $5,000 or more. Health insurance may cover some costs, but coverage varies widely.

Virtual & Online Options

Many FDN Practitioners offer virtual consultations and online programs, providing accessibility for those unable to find a local practitioner or who prefer the convenience of remote sessions. Virtual sessions can be conducted via video conferencing platforms, allowing for face-to-face interaction and screen sharing to review lab results and treatment plans. Online programs may include educational modules, meal plans, and support groups. However, in-person sessions may be preferable for those who value direct interaction or require physical assessments. Local practitioners may also have established relationships with labs and other local health resources.


FDN Practitioners must complete a comprehensive training program and pass a certification exam administered by the Functional Diagnostic Nutrition Institute. The FDN certification program covers topics such as functional lab testing, anatomy and physiology, nutrition, lifestyle modification, and business practices. Some FDN Practitioners may have additional certifications in areas such as nutrition, health coaching, or specific lab testing methodologies. While not required, many FDN Practitioners also have backgrounds in healthcare fields such as nursing, medicine, or chiropractic care.

Complementary Practices

Functional Diagnostic Nutrition (FDN) can be complemented by a variety of practices that support overall health and well-being. These include: 1) Nutritional therapy, which focuses on optimizing diet and nutrient intake to support bodily functions and address deficiencies. 2) Lifestyle coaching, which helps individuals develop healthy habits and routines related to sleep, stress management, and physical activity. 3) Mind-body practices like meditation, yoga, and deep breathing exercises, which can help reduce stress, improve mental clarity, and promote relaxation. 4) Functional medicine, which takes a holistic approach to health by addressing the root causes of symptoms and imbalances. By integrating these complementary practices with FDN, practitioners can provide a comprehensive approach to supporting their clients' health and well-being.

Practitioner Types

FDN Practitioners come from a variety of professional backgrounds, including: 1) Nutritionists and dietitians who specialize in using food as medicine to support optimal health. 2) Health coaches who help clients develop healthy lifestyle habits and overcome barriers to wellness. 3) Naturopathic doctors who use natural remedies and therapies to support the body's innate healing abilities. 4) Chiropractors who focus on optimizing the function of the nervous system and musculoskeletal system. 5) Acupuncturists who use traditional Chinese medicine techniques to balance the body's energy and promote healing. 6) Nurses and physician assistants who incorporate functional medicine principles into their practice. Regardless of their specific background, all FDN Practitioners share a commitment to using functional lab testing and personalized protocols to help their clients achieve optimal health.

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  • Q: What is Functional Diagnostic Nutrition (FDN)?

    • A: Functional Diagnostic Nutrition (FDN) is a holistic approach to health that focuses on identifying and addressing the root causes of symptoms and imbalances in the body. FDN Practitioners use functional lab testing to assess various aspects of health, including digestion, hormones, immune function, and detoxification. Based on the results of these tests, they develop personalized protocols that may include dietary changes, nutritional supplements, lifestyle modifications, and other natural therapies to support the body's innate healing abilities and promote optimal health.
  • Q: How does FDN differ from conventional medicine?

    • A: FDN differs from conventional medicine in several key ways. While conventional medicine often focuses on managing symptoms with medications or surgery, FDN aims to identify and address the underlying causes of health issues using natural, non-invasive approaches. FDN Practitioners take a holistic view of health, considering the complex interactions between different systems in the body, as well as the impact of lifestyle factors like diet, stress, and environmental exposures. They use functional lab testing to gain a deeper understanding of each client's unique physiology and develop personalized protocols to support healing and optimal function.
  • Q: What types of health issues can FDN help with?

    • A: FDN can be helpful for a wide range of health issues, including digestive disorders, hormonal imbalances, autoimmune conditions, chronic fatigue, skin problems, and mood disorders. By identifying and addressing the root causes of these issues, FDN Practitioners aim to support the body's natural healing processes and promote lasting health and well-being. However, it's important to note that FDN is not a substitute for medical treatment, and individuals with serious health concerns should always consult with a qualified healthcare provider.
  • Q: What can I expect during an FDN consultation?

    • A: During an initial FDN consultation, the practitioner will typically review your health history, current symptoms, and lifestyle factors. They may also recommend functional lab tests to assess various aspects of your health, such as digestion, hormones, immune function, and nutrient status. Based on the results of these tests and the information gathered during the consultation, the practitioner will develop a personalized protocol that may include dietary recommendations, nutritional supplements, lifestyle modifications, and other natural therapies. Follow-up consultations are typically scheduled to monitor progress, make adjustments to the protocol as needed, and provide ongoing support and guidance.
  • Q: How long does it take to see results with FDN?

    • A: The time it takes to see results with FDN can vary depending on the individual and the complexity of their health issues. Some people may start to notice improvements in their symptoms within a few weeks of starting an FDN protocol, while others may take several months to see significant changes. It's important to remember that FDN is a holistic approach that aims to support the body's natural healing processes, which can take time. Consistency and patience are key, as well as working closely with an FDN Practitioner to monitor progress and make adjustments as needed.


Functional Diagnostic Nutrition (FDN) offers a comprehensive, holistic approach to health that empowers individuals to take control of their well-being. By identifying and addressing the root causes of symptoms and imbalances, FDN Practitioners help their clients achieve optimal health and vitality. Through the use of functional lab testing, personalized protocols, and a focus on natural, non-invasive therapies, FDN supports the body's innate healing abilities and promotes lasting wellness. Whether you're struggling with chronic health issues or simply looking to optimize your health and prevent future problems, working with an FDN Practitioner can be a valuable investment in your overall well-being. By taking a proactive, holistic approach to health, FDN offers a path to greater energy, vitality, and resilience in the face of life's challenges.