What would happen if the CEO of a company didn’t know basic metrics regarding the health of the business?

The CEO strolls into the monthly board meeting. No handout is delivered, no laptop tucked beneath his arm. He takes a seat and waits for the meeting to begin. The board members, confused and slightly concerned, begin to ask questions on the latest figures: monthly sales revenue, costs, profit margin, and year-over-year growth. He sits back in his chair and answers: “I have no idea. The accounting department is in charge of that information. If there’s a problem, I’m sure they’ll notify me.”

We can’t imagine a successful company operating this way. But when it comes to our own basic health metrics, we often have no idea. We place the burden of responsibility in the hands of our healthcare system, assuming that if there’s an issue, surely they’ll notify us. The problem with this assumption: it’s false. 

Our healthcare system is structured to react, not prevent. Say you were to get hit by a car and rushed to the hospital – the doctors and nurses would know exactly how to treat your broken bones and bruises. But if you were to approach the same healthcare system with the intent to prevent or push off the onset of a chronic disease, our confidence in the system dwindles.

To understand what’s going on (and what’s going wrong), we must consider the critical distinction between “normal” and “optimal” health. Let’s look at the example of vitamin D, the sunshine vitamin. Vitamin D is a prohormone (a substance that your body converts to a hormone). It travels through your blood and tissues like a Wi-Fi signal, entering your cells. Once inside, it binds to a receptor molecule called VDR (vitamin D receptor), allowing vitamin D to enter the nucleus (which houses your DNA) and turn on over 900 genes. Some affect bone metabolism, others suppress tumor formation, others reduce inflammation, and others are essential for creating and maintaining brain synapses. 

A “normal” range for vitamin D is 20-79 ng/mL. A level lower than 12 ng/mL would indicate a deficiency. However, studies have shown that low vitamin D levels are associated with an increased risk of cardiovascular disease, cognitive impairment, bone loss, depression, and weakened immunity. Ongoing studies are being conducted looking at the correlation between lower vitamin D levels and higher COVID-19 mortality rates. More recent studies have revealed that optimal levels of vitamin D – those associated with increased immunity, cognition, vascular health, etc. – are within the range of 50-80 ng/mL. 

The last time I checked my own levels, I had a vitamin D of 21 ng/mL. No surprise there; it was winter in San Francisco, and I’m a Cold Weather Wimp. Perhaps just as unsurprisingly, I wasn’t notified that I was on the lower end of the normal spectrum, nor given the risks associated with low levels. Because I wasn’t yet critically deficient, there was no follow up.  And so, completely oblivious, I was living each day with ongoing risk for multiple future diseases.

So what is a “normal” range for a blood test, anyway? A normal range is simply two standard deviations above and below the mean of a population presumed to be free of disease. “Normal” has nothing to do with optimal health. And the sicker our population becomes, the more a normal range skews toward – and allows for – suboptimal “normal” results. Why should we find this alarming? Well, in other words, our population’s health is directly dictating our health standards, rather than the other way around.

When is “normal” not normal? Homocysteine (a biomarker of inflammation and methylation) is considered “normal” up to 12.9 umol/L, but there is clear and published evidence showing that as your homocysteine levels increase above 6 umol/L, the rate at which your gray matter shrinks as you age also increases. While the low threshold of vitamin B12 (essential to red blood cell formation) is 200 pg/mL, you’ll often see a footnote to the results, explaining that “normal” levels between 200-300 pg/mL may be associated with vitamin B12-deficiency-related diseases such as dementia. 

In 1997, the American Diabetes Association and federal government lowered the diagnostic threshold for type 2 diabetes from a fasting glucose of 140 to 126 mg/dL; this shift in the definition of “normal” increased the number of Americans classified as diabetic by nearly 2 million overnight. As you can see, we cannot and should not blindly trust that normal results are reliably predictive of good health outcomes. 

Becoming the CEO of our own health starts with keeping a pulse on our own health metrics. Our unquestioned faith in normal values now debunked, we can rely instead on scientific evidence to define what is optimal. With the advancement of wearable tech like Fitbit or Oura Ring, and direct-to-consumer lab testing like DirectLabs or Everlywell, we have more access, control, and connection to our data than ever before. We can simultaneously place trust in our heroic doctors to save us, should something go wrong, while acknowledging that strategies for disease prevention ultimately rest in our own hands. We don’t need a medical degree to empower ourselves with some basic data. After all, not even the best doctor in the world cares as much about your future health as you do. 

By following these basic health metrics, you are on your way towards becoming the rightful CEO of your own health:

Hemoglobin A1c

  • Optimal Range: 4.0% – 5.2%
  • A measure of: your average blood glucose levels over time (2-3 months).
  • Why it’s important: Insulin resistance is a major contributor to chronic disease in America. Maintaining your hemoglobin A1c in the optimal range will help prevent or even reverse insulin resistance.


  • Optimal Range: < 7 umol/L
  • A measure of: inflammation, methylation, and toxicity.
  • Why it’s important: A buildup of this toxic amino acid can indicate inflammation and/or poor methylation, a biochemical process essential for the proper function of almost all of your body’s systems. 


  • Optimal Range: < 0.9 mg/dL 
  • Measure of: inflammation.
  • Why it’s important: Inflammation is at the root of every one of the major chronic age-related diseases: heart disease, cancer, diabetes, dementia, among others.

Triglyceride:HDL Ratio

  • Optimal Range: 0.7 – 1.5
  • Measure of: vascular health.
  • Why it’s important: While cholesterol has been vilified for decades, the right amount of cholesterol is indeed necessary for optimal health! Your total cholesterol is not a great measure of cardiovascular risk, but your triglyceride to HDL ratio is one of the best predictors of vascular health.

Vitamin D

  • Optimal Range: 50 – 80 ng/mL
  • Measure of: overall health: trophic support, calcium absorption, cognition, mood, and other functions.
  • Why it’s important: Vitamin D has several functions critical to health, including regulating calcium absorption for bone health, supporting immune function, regulating mood, and enhancing cognition. 


  • Tess Bredesen

    Cognitive Nutrition Director at Thrive Global, Cognitive Health Nutritionist, National Board Certified Health & Wellness Coach

    Tess Bredesen is Thrive Global’s Cognitive Nutrition Director and an expert on the prevention of cognitive decline. She is the founder of Sia Health, a practice which specializes in the implementation of the Bredesen Protocol, the first program proven to prevent and reverse cognitive decline. She works with clients internationally through one-on-one online consultations, developing and coaching to adopt programs customized to an individual's risk factors. Find brain-boosting recipes, interviews, and program details at www.siabrainhealth.com.