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Understanding Laboratory Reference Ranges: A Functional Medicine Perspective

This blog is definitely overdue and dives into a topic that plays an integral role in patient care: laboratory reference ranges. In the world of functional medicine, a holistic and patient-centered approach, understanding these reference ranges is crucial. I've always been a bit of a lab geek, and one of my favorite parts of my early years as a bedside nurse was monitoring trends in my hospitalized patients, watching their labs change based on the support they were receiving, and educating them on their lab results and overall progress. But before we delve into the functional significance specifically, let’s consider some labwork basics.


What Are Laboratory Reference Ranges?

Laboratory reference ranges, often simply called "normal ranges," are the range of values that 95% of the "healthy" population falls into when tested for a particular marker. It's important for me to highlight "healthy" population because this is simply a sampling of averages from the local population that does not acknowledge a diagnosable disease when the bloodwork is drawn. After many years as a functional NP, a primary care NP, and before that, a bedside nurse since 2009, I can say that, at least in the United States, our average population without a diagnosable disease is still cardiometabolically quite unhealthy. It's also important to note that these values don't necessarily denote what's "optimal" for health—just what's considered "normal" based on this statistically cardiometabolically unhealthy population data.

As a result of these less-than-ideal reference ranges established using a fairly unhealthy sample population in most cases, our patients may come to us feeling poorly, but with "all normal labs." When a patient presents with a health concern, gets diagnostic testing that comes back "all normal", and is then told there is no explanation for their health concerns, they can feel unheard and dejected. I have seen this in my career too many times to count, and I imagine most nurses can relate! I have definitely been guilty of doing this as a primary care provider despite my best intentions!


A great example of this is a patient coming in complaining of fatigue. There are so many potential causes of fatigue, and this is an extremely common chief complaint in primary care. A normal workup might include evaluating sleep habits, a depression screening, a physical exam, and probably a complete metabolic panel (CMP), a complete blood count (CBC), testing the thyroid stimulating hormone (TSH), and maybe a bit more investigative work. This I would consider to be fairly common care, but what happens after this visit is the problem. If a patient's CBC, CMP, and TSH come back "normal", that tends to be the end of the story and the patient leaves with no answers. This happens EVERY DAY in healthcare.


How Are Reference Ranges Established?

To be more specific on the actual process, it typically follows these steps:

  • Collect Data: Labs collect blood samples from a reference group, as I mentioned, a group deemed to be "healthy" based on certain criteria.

  • Statistical Analysis: The results are subjected to statistical analysis. Most laboratories define their reference range as the interval between the 2.5th and 97.5th percentiles, which means 95% of the "healthy" population will fall within this range.

  • Regular Updates: As new research emerges and populations change, labs may adjust these ranges. Moreover, different labs might have slightly different reference ranges based on their methodologies and populations studied.

Functional Medicine’s Take on Reference Ranges

In functional medicine, we don’t just look at whether a patient's values fall within the "normal" range. Instead, we aim for "optimal" ranges, which might be narrower and more specific. These optimal ranges are based on where most people feel and function their best, and not just where they avoid disease.

For example, while a conventional lab might consider a TSH (thyroid stimulating hormone) level of 4.5 within the normal range, functional practitioners might aim for a value between 1 and 2, where many patients report feeling their best. This optimal range varies depending on the actual marker being measured. And in the case of TSH, it isn't even a thyroid lab value and shouldn't be used alone to diagnose or rule out thyroid dysfunction, which is a whole other blog post topic!


My students often ask me for a literal number for optimal labs, but the truth is that every lab has slightly different ranges they are using, and this makes having an ideal number variable depending on their local values. Fortunately, I am able to share more of what to look for in various types of markers when I am teaching this concept to my RN and NP students because motivated patients need someone to help them in their efforts to achieve optimal wellness! We have too many people in our society looking for an informed, holistic partner on their healthcare journey, and functional nurses can absolutely be the perfect partner for these patients!


Importance for Nurses and Nurse Practitioners

Being on the front lines of patient care, it's crucial for us to:

  • Interpret Lab Results Thoughtfully: Understand the difference between "normal" and "optimal." A patient can have values within the normal range and still experience symptoms.

  • Consider Individual Variability: Genetics, diet, lifestyle, and other factors mean what’s optimal for one patient may differ for another. Did you know stress can impact our body's demand for various nutrients?! Our modern, high-stress lifestyles are one of the leading causes of our increasing prevalence of nearly every chronic health concern, and our patients need to hear this from someone that they trust!

  • Educate & Advocate: Empower patients with knowledge. If their values are within the “normal” range but not “optimal,” they should know their options and potential implications. They should also have a partner in developing an action plan to achieve the optimal wellness they deserve!

The Bigger Picture

Remember, a lab value is just a snapshot of a patient’s health at a particular moment. While important, it's just one piece of the puzzle. Symptoms, medical history, physical examination, and other diagnostics play equally significant roles. Functional nurses and nurse practitioners are able to look at the patient from a holistic viewpoint, and they are able to use lab work as one tool in providing true root cause healing. As functional nurses and nurse practitioners, we have a unique opportunity to bridge the gap between "normal" and "optimal," ensuring our patients not only live but thrive.


Learn more via the course I teach exclusively to RNs and NPs through the Integrative Nurse Coach Academy in partnership with the Institute for Functional Medicine- Functional Medicine for Nurses™

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