Second Opinion · Octo Health with Catarina Costa, MD
Your results came back normal. That is not the same as healthy.
It is the most common thing people hear after bloodwork. Everything is normal. And it feels like an answer. But "normal" is a narrower word than most people think, and it was never built to tell you whether you are doing well. It was built to tell you whether you are clearly sick. Those are two different questions.
What "normal" actually means
A lab reference range is built in a specific way. The lab measures a marker across a group of people and draws the line around the middle 95 percent of the results, the 2.5th to the 97.5th percentile. The rest fall outside. That is the formal definition.[1]
So "normal" means one thing: you resemble most of the people the lab sampled. By design, 1 in 20 perfectly healthy people fall outside the range. And nothing about that range describes where your health is at its best. It describes where the average person sits. The range exists to catch disease, not to define thriving.
Why "in range" can still be a problem
Because the range is wide, a result can sit comfortably inside normal for years while your body is already compensating hard underneath it.
The label is a snapshot. Your health is the line over time.
The clearest example: fasting insulin
Fasting insulin is the marker that makes the gap between normal and optimal impossible to ignore.
The standard Quest Diagnostics reference range calls anything from 2.6 to 24.9 µIU/mL normal. Many clinicians in preventive and longevity medicine work to a tighter range, commonly cited as roughly 2 to 6 µIU/mL, though this is not a standardized reference range.[3,4] That is not a small difference. A result of 18 is "normal" on your report and well outside optimal at the same time.
Here is why it matters. Insulin rises before glucose does. You can have a fasting glucose of 88 mg/dL, textbook normal, while your fasting insulin is already 18, quietly signaling years of compensated insulin resistance. The pancreas works overtime to keep glucose normal, often for a decade, before blood sugar ever moves and long before HbA1c crosses any line.[2,4]
So a number can be normal and still be the earliest warning you will get. Normal said nothing was wrong. Optimal said the work had already started.
See your own numbers, on one timeline.
Octo unifies your records, labs and notes, so you see the line, not a single dot.
Where "optimal" comes from, and its limits
Optimal ranges come from asking a different question. Not "where does disease begin," but "where do long-term outcomes tend to look best." One honest caveat: optimal ranges are less standardized than reference ranges. They vary by source, they are still debated, and they depend on you. They are a tool for a better conversation with your doctor, not a verdict to act on alone.
The part that matters more than either label
Here is what neither word captures on its own: a single number tells you very little. The same number, tracked over time, tells you almost everything.
A fasting insulin of 9 means one thing if it has been climbing, and something else entirely if it has dropped from 16 over the past year. The label is identical. The story is opposite. Pairing fasting insulin with HOMA-IR and HbA1c across consecutive tests is how you read the trajectory, not just the dot.
That is the whole idea behind keeping your results on one timeline instead of scattered across portals and PDFs. Not to replace your doctor. To give you, and them, the full line.
What to do with this
Know your actual numbers, not just the word "normal." Ask your doctor what optimal looks like for you, given your history and your goals. And track the markers that matter over time, so the trend is visible before the next visit, not after.
Normal tells you that you are not sick. It does not tell you that you are well.
Healthcare stores data. Octo gives it memory.
Walk into your next appointment with everything.
One place for every result, note, test and symptom. Yours.
For educational purposes only. This article presents published clinical research to help you have a more informed conversation with your physician. It is not medical advice, a diagnosis, or a treatment recommendation. Reference and optimal ranges vary by lab and by individual. Always consult a licensed healthcare provider.
References (Vancouver)
Clinical and Laboratory Standards Institute. Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Guideline. 3rd ed. CLSI document EP28-A3C. Wayne (PA): CLSI; 2010.
Reaven GM. Role of insulin resistance in human disease. Diabetes. 1988;37(12):1595-1607.
Kraft JR. Diabetes Epidemic & You. Trafford Publishing; 2008.
Attia P. Outlive: The Science and Art of Longevity. New York: Harmony Books; 2023.
