Evidence-based medicine is often described as the intersection of three elements: the best available research, clinical expertise, and patient preferences. Most of the articles I write focus primarily on the research side of that equation, reviewing studies and translating emerging science into practical strategies for long-term health. Today I’d like to focus more on the clinical expertise side, discussing patterns that emerge over years of day-to-day patient care.
Most of us assume that “normal” means healthy. But in medicine, normal often just means common. What does it really mean when your lab results are normal, yet you don’t feel your best?
Part of the answer lies in how lab reference ranges are designed. They measure values across populations and generally define the middle 95 percent as “normal.” (1) But as populations become less healthy, some normal values can shift, reflecting common patterns rather than what is truly optimal. Individual physiology isn’t simply normal or abnormal. Think of it more like a thermostat, constantly adjusting to internal and external conditions and context is needed to turn data into insight.
In the U.S., carrying excess body weight has become statistically common, yet few would argue that being overweight is a desirable goal. At the same time, not all individuals who carry excess weight experience health complications, and not every person with a normal body weight is disease-free. Human health is more nuanced than that. Laboratory values can follow a similar pattern: a result may fall within the population reference range while still reflecting physiology that could be functioning better.
Reference ranges show what is common but common is not always optimal.
Think in terms of reserves. Imagine a bank account with $100,000 that you gradually draw from without making deposits. If a professional advised you to intervene only once the balance reached $100, you’d likely question that strategy. Yet many medical thresholds work this same way: disease is flagged only after it crosses a specific threshold often following years of decline.
Our bodies are remarkably resilient in youth, often masking small declines in physiology. But changes begin accumulating sooner than most realize. Many people think of 50 as midlife but based on the average U.S. life expectancy of 79, (2) midlife starts closer to 39 or 40. In my experience, it’s around this early midlife point that subtle physiological shifts first become apparent. Taking action at this stage allows us to build health reserves before deficits accumulate.
Once dysfunction sets in, restoring optimal health becomes far more difficult than maintaining it. Preserving health is almost always easier and more effective than trying to rebuild it later. That said, even optimization has limits. Even well-intentioned strategies, such as excessive or unnecessary supplementation can create new problems. Prevention and optimization work best when individualized and guided by clinical insight and judgment.
To be clear, reference ranges remain essential; they flag disease and guide care but they reflect population averages, not personal optimums. Preventive medicine goes beyond avoiding abnormal labs. It’s about maintaining the reserves that allow the body to function well for decades. Understanding the difference between normal and optimal empowers individuals to act early, before subtle shifts become overt disease.
Prevention, by definition, must begin before things break. Like a leak in a roof, the longer it’s ignored, the more damage it causes and the more extensive the repair becomes.
1. Doles, N., Ye Mon, M., Shaikh, A., Mitchell, S., Patel, D., Seehusen, D., & Singh, G. (2025). Interpretating normal values and reference ranges for laboratory tests. The Journal of the American Board of Family Medicine, 38(1), 174–179. https://doi.org/10.3122/jabfm.2024.240224r1
2. Centers for Disease Control and Prevention. (2026). Mortality in the United States, 2024. Centers for Disease Control and Prevention. https://www.cdc.gov/nchs/index.html
