Interview with Susannah Kerwin, Nurse Practitioner and Owner of Tendwell

People & Products

October 5, 2023

1. Can you tell me about the development and growth of Tendwell?

Tendwell was born from my desire to provide a kind of comprehensive, holistic and integrative care to patients that is not possible in traditional primary care. At the time of Tendwell’s inception, I had been working in a primary care office in Soho, NYC for about ten years. I was happy to start out in this setting, but soon found it limiting. I could see that my patients’ issues were often more deeply rooted than standard approaches would suggest, but, like most medical offices, the practice was not so set up for the comprehensive, personalized approach I hoped to employ. I needed more time with each patient. I also needed more autonomy to set up the model that would support holistic health strategies. I needed to become my own boss. The catalyst came in the form of COVID-19. Like many people, experiencing a global pandemic forced me to confront my own values and personal aspirations. So, I left the practice and started Tendwell. Now, it was certainly not this instantaneous—I had been slowly incorporating some functional health strategies into my primary care practice all along—for example, I used expanded testing and brought a focus on modifiable lifestyle factors wherever possible. Simultaneously, I built my knowledge base through studies with the Institute of Functional Medicine (IFM). I also had some personal health experiences—a child diagnosed with PANDAS—that really influenced my thinking about what works in healthcare. The pandemic just nudged me along.

2. Tell me about your entry into functional medicine and what you feel it provides patients that perhaps conventional medicine cannot? 

I first heard about functional medicine during grad school at NYU when I was placed in a functional medicine clinic for some of my training hours. It was a group of about 5-6 different providers, mostly MDs who were prescribing bioidentical hormones, vitamin drips, and treatments for chronic illnesses like chronic Lyme disease or chronic fatigue syndrome. Then after I graduated as an NP I worked a couple of part-time jobs—one where I was trained to do trigger point therapy & work side by side with chiropractors for patients with chronic pain and another working with a brilliant MD who had a small but busy insurance-based primary care practice with a side of functional medicine. This all dovetailed nicely with an experience I’d had a couple of years before: I had moved to Beijing China for a year and was successfully treated by a Chinese doctor for an issue that had stumped my Western docs. I had seen at least three MDs in San Francisco and all they could offer was painful, time consuming and costly treatments that did not work. The Chinese MD looked at me differently and said that we needed to stimulate and support my immune system. She gave me a few herbals and some supplements to take—a month later, I was better. It was astonishing to me. I knew then and there that I wanted to approach healthcare like this. Through my functional medicine practice, I can provide patients the kind of insight and personalized medicine that I received in China. Above all else, in functional medicine, the focus is on root causes and taking the time to really explore what is going on with a patient’s body systems. Conventional medicine, with the imperatives of high throughput, insurance company demands and many other structural issues, just can’t do the things a functional medicine doctor can.

3. Can you tell me about the services you offer in your practice and what type of patients you love working with?

In my current practice, I am offering functional medicine with a side of primary care. It’s more of a boutique style practice—fewer patients, longer visits, increased access to the provider, flexibility for everyone. I am excited to be on the path with each patient—collaborating on their health goals. Most times, I will start with an in-depth 1 st and 2 nd appointment where we gather all the information, and an extensive medical history, personal history so I can get a sense of the person I am working with. This is also the time to obtain some baseline functional medicine labs—centered around potential nutritional deficiencies, genetics, inflammatory markers…etc. I love working with patients who are ready to investigate and do the sometimes-difficult work required. I love working with patients who have migraine headaches, thyroid dysfunction, IBS, SIBO and digestive issues especially.

4. Can you speak to the role of functional lab testing in your practice and how you individualize treatment plans based on lab testing?

Functional medicine testing is very exciting. There are so many appealing tests! Most times, I start with baseline nutritional testing. Because these are standard tests, they are often covered through insurance and patients can go to standard lab companies like Quest and Labcorp, which (for all their faults) can be convenient. I see these tests as pretty necessary. “Test don’t guess”—I’ve been taught. We use these tests to identify areas that need support. I also use validated questionnaires to guide treatment. I may see someone over a year and then decide, hey, you could really benefit from stool microbiome testing. It’s all about learning more and more about your body and where you are at now—at this moment in time while considering the factors that led you here. As always, we do all this exploration with your specific health goals in mind.

Some other tests I like a lot are the DUTCH tests for hormones, screening for toxic heavy metals, and other toxic exposures. Everything is individualized. Some people come to me straight from other clinicians who have just had bloodwork done. I always look at what was done and try to fill in the gaps and complete the picture from the functional medicine perspective.

5. Can you talk a little bit about functional medicine as it relates to mental health-what concerns do you see come up in your practice and do you have specific functional approaches to help with mental health concerns? 

Mental health concerns come up for almost every patient I work with whether it is a previous diagnosis of ADHD, anxiety, depression, panic, OCD, PMDD or even nervousness with work presentations. Mental health concerns are often prevalent, and sometimes ebb and flow over a person’s lifetime, as you know. My favorite ways to support mental health, looking through the functional medicine lens, involve nutrition, supplements, stress management, exercise and sleep optimization. Without doing any testing at all, I’d start there. I’d also start by looking at what the client has tried to implement, what has and hasn’t worked, what they think of as normal andwhere they would they like to be. Sometimes it feels overwhelming to patients to figure out where to begin. But, over time working with patients, we can tease out areas that need support and take specific action. For example, optimizing Omega 3 levels and Vitamin D3 levels can make a big difference for many people. Also, looking into daily cortisol and DHEA patterns can also give us and the client additional evidence about the effects of modern-day stressors on physiology. I love doing a 4-point salivary Cortisol Awakening Response (CAR) test for this reason. These are just a few examples. The tight connection between functional health of the body and mental health really plays an important part in the Tendwell practice.

6. Can you share a bit about your own healthy lifestyle practices? 

Sure! I have always been quite active—I find it especially helpful for my own mental health to incorporate exercise (nature’s Prozac) into my week. Right now, I participate in Pilates classes twice a week. My husband is training to hike a fourteener so I am running with him once a week on weekends. I also try to get in another run by myself each week—this doesn’t always happen with weather and work but it is my goal to exercise 4 days a week (but no more—I find that working out more than that actually elevates my stress levels).

I love listening to podcasts, so I try to at least listen to something that is not medical or political weekly—one of my favorite comedic/feel-good podcasts is Heavyweight on Spotify produced by Jonathan Goldstein. I try to incorporate the advice I give to patients into my own life as well. I’ve paid close attention to nutrition since high school and have experimented over the years with many different dietary approaches. Most recently I’ve been eating 100% gluten free. It’s been a fun culinary challenge and it’s helped me avoid indulging in too many sweets. Mostly, what works for me is eating three regular meals a day even if I am not officially hungry. Also helpful: staying away from sweets as a meal—at least getting a base of protein and veggies on board before I have a sweet treat—and drinking lots of water (especially since I moved to Colorado).

I also have the goal of getting into an infrared sauna once a week and have a membership at Restore Hyperwellness in Denver. I love trying out new self-care modalities. My next focus will be working on heart rate variability with a system many functional medicine clinicians use called HeartMath. 


I want to extend my heartfelt thanks to Susannah for her pioneering work in the field of women’s healthcare. Her dedication to addressing root causes and optimizing health aligns seamlessly with the core values of Tend to Her, and together, we strive to empower women to make the best choices for their well-being during pivotal life stages. The importance of our work cannot be overstated, and it is through collaborative efforts like these that we can truly make a difference in the lives of those we serve.

Find Susannah’s practice here: https://www.tendwellhealth.com