You know your Social Security number, your ATM pin code, and your mom’s phone number. But do you know your HbA1c?
According to Dr. Florence Comite, founder of the Comite Center for Precision Medicine & Healthy Longevity, five numerical biomarkers can reveal how well you’re aging and warn of trouble long before symptoms of disease appear. And the most crucial among them — fasting insulin — is also the most overlooked .
Dr. Comite, a Yale-trained endocrinologist who founded Women’s Health at Yale in 1992 and has been practicing precision medicine for over two decades, recommends starting to monitor these biomarkers between the ages of 25 and 30 .
“By the time symptoms send you to a doctor, the process has often been underway for quite some time, usually decades,” Comite told The Post. “If you want to be proactive to stop aging disorders rather than react to disease, you should establish your baseline early and track how your body changes over time.”
Her upcoming book, “Invincible: Defy Your Genetic Destiny to Live Better, Longer,” is set to be published by Little, Brown Spark on April 28, 2026 .
Here is everything you need to know about these five key biomarkers — and why the one you’ve probably never heard of matters most.
Biomarker #1: Fasting Glucose — The Basic Blood Sugar Check
A fasting glucose test measures blood sugar after an overnight fast to screen for prediabetes or diabetes.
| Category | Fasting Glucose Level (mg/dL) |
|---|---|
| Normal (standard range) | 70–99 |
| Prediabetes | 100–125 |
| Diabetes | 126+ |
But Dr. Comite uses a tighter, more optimal range based on research:
“I like to see fasting glucose in the 70s to 80,” she said. “Once you are consistently above 80, into the 90s or above, especially paired with elevated insulin, that is an early warning sign of impending prediabetes with insulin resistance.”
Research supports the power of fasting to improve metabolic health. A study published in Nature Communications found that periodic fasting-mimicking diets were associated with reduced insulin resistance and other pre-diabetes markers, along with a decrease of 2.5 years in median biological age .
Biomarker #2: Fasting Insulin — The Most Crucial and Most Overlooked
“Fasting insulin is one of the most crucial — and most overlooked — biomarkers in medicine because it reveals how hard your body is working to stabilize your glucose,” Dr. Comite explained.
The pancreas produces insulin, which regulates blood sugar by allowing glucose to enter cells for energy. A fasting insulin test measures the amount of insulin in the blood after an 8- to 12-hour fast to see how well the body manages blood sugar.
The key insight: You can have healthy glucose values and elevated insulin.
“In my clinical practice, I like to see fasting insulin less than 2, though reactive, conventional medical practitioners typically reference 2–5 [micro-international units per milliliter] as ‘normal’,” she said. “Once you start creeping above that, into the high single digits or teens, it’s a red flag that metabolic dysfunction is already underway — even if other labs still look ‘normal.’”
Research confirms the importance of monitoring fasting insulin. A study on type 1 diabetes patients found that an overnight fast decreased harmful advanced glycation end products (AGEs) by 21-58% while increasing protective sRAGE isoforms by 22-24% . These findings suggest that even short-term fasting can improve metabolic health markers.
Biomarker #3: HbA1c — Your 3-Month Glucose Average
HbA1c (hemoglobin A1c) reflects your average glucose over approximately three months. Red blood cells live for about three months, so the test provides an average picture of blood sugar levels over that period .
| Category | HbA1c Level |
|---|---|
| Normal (standard range) | Below 5.7% |
| Prediabetes | 5.7% – 6.4% |
| Diabetes | 6.5% or higher |
Dr. Comite aims for stricter targets:
“I like to see under 5.0%,” she said. “Once your hemoglobin A1c moves up above that, it signals changes in your system’s carbohydrate management, especially beyond 5.6%, at which you have become prediabetic with metabolic dysfunction.”
She recommends checking HbA1c at least once or twice a year — and perhaps more often if you’re trying to optimize your metabolism.
For individuals already diagnosed with diabetes, the American Diabetes Association generally recommends an A1c goal of below 7% to reduce the risk of long-term complications .
Biomarker #4: Cholesterol Risk Ratio — Beyond Good and Bad
Cholesterol can be confusing because there’s “good” cholesterol (HDL) and “bad” cholesterol (LDL). But Dr. Comite argues that your LDL “doesn’t tell the whole story.”
Instead, she recommends looking at your Cholesterol Risk Ratio (CRR) — your total cholesterol divided by your HDL cholesterol — to get a better sense of your heart disease risk.
“Optimal CRR is 2 or under,” Dr. Comite said. “A higher ratio, over 2, suggests increased cardiovascular risk, even if LDL isn’t dramatically elevated. Elevated CRR beyond 3.5 to 4 connotes even greater risk.”
The importance of aggressive cholesterol targets is reflected in modern guidelines. The National Institute for Health and Care Excellence (NICE) recommends that for secondary prevention of cardiovascular disease, clinicians should aim to keep patients’ LDL cholesterol levels at or below 2.0 mmol/L (approximately 77 mg/dL) .
Biomarker #5: Free Testosterone — Not Just for Men
Testosterone is often thought of as a male hormone, but women need it too. It drives energy, libido, muscle mass, metabolism, and mood in both genders.
Dr. Comite always tests her patients — both men and women — for “free” testosterone, which is the biologically active, immediately usable testosterone in the blood that is not bound to proteins.
“As levels drop, we see loss of muscle, increased fat accumulation around the trunk, especially visceral fat, and worsening insulin resistance,” she said.
According to Dr. Comite, optimal free testosterone levels are:
| Gender | Optimal Free Testosterone (pg/mL) |
|---|---|
| Men | 180–250 |
| Women | 18–25 |
Research supports these concerns. A study published in the Journal of Clinical Endocrinology & Metabolism found that higher free testosterone levels in older women were associated with greater bone mineral density and lean body mass .
Dr. Comite, who has been prescribing testosterone for decades, points to a landmark 2023 study in the New England Journal of Medicine that tracked more than 5,200 men with low testosterone and found that testosterone replacement therapy did not increase the risk of heart attack or stroke compared to a placebo .
Putting It All Together: The Interconnected View
Taken together, these five biomarkers reveal how well or poorly your system is operating. Dr. Comite emphasizes that they should not be viewed in isolation:
“You need to view these interconnected biomarkers in relation to one another and other factors such as body composition, personal medical and family health history, and how you live your life. Sleep, food, exercise, stress, and environment, such as toxins, all play a role and should be factored into an assessment.”
Recent research supports this holistic approach. A study on the metabolic transition between fasting and feeding found that fasting reprograms the plasma metabolome, affecting aging-associated metabolites including glucose, amino acids, and ketone bodies .
The Bottom Line: Start Monitoring Early
Dr. Comite recommends establishing baseline levels for these five biomarkers between ages 25 and 30. Early detection of metabolic dysfunction allows for lifestyle interventions — including nutrition, exercise, sleep optimization, and stress management — before disease develops.
| Biomarker | Optimal Target (Dr. Comite) | Standard “Normal” Range |
|---|---|---|
| Fasting Glucose | 70–80 mg/dL | 70–99 mg/dL |
| Fasting Insulin | < 2 µIU/mL | 2–5 µIU/mL |
| HbA1c | < 5.0% | < 5.7% |
| Cholesterol Risk Ratio | ≤ 2.0 | Varies |
| Free Testosterone (Men) | 180–250 pg/mL | Varies by lab |
| Free Testosterone (Women) | 18–25 pg/mL | Varies by lab |
“Your genes do not have to be your destiny,” Dr. Comite writes in her forthcoming book . “Adding candles to your birthday cake is inevitable. Aging well makes you invincible.”
FAQ: Key Biomarkers for Healthy Aging
Q: What is the most overlooked biomarker for aging?
A: Fasting insulin. Dr. Comite calls it “one of the most crucial — and most overlooked — biomarkers in medicine” because it reveals how hard your body is working to stabilize glucose.
Q: When should I start monitoring these biomarkers?
A: Between ages 25 and 30, according to Dr. Comite.
Q: How often should I check HbA1c?
A: At least once or twice a year, or more often if optimizing metabolism.
Q: What is a good Cholesterol Risk Ratio?
A: Optimal is 2 or under. Over 2 suggests increased cardiovascular risk.
Q: Do women need testosterone?
A: Yes. Testosterone drives energy, libido, muscle mass, metabolism, and mood in both genders.
Q: What is Dr. Comite’s book about?
A: “Invincible: Defy Your Genetic Destiny to Live Better, Longer” provides a proactive, precision medicine approach to healthy longevity. It publishes April 28, 2026 .