The Early Warning Sign Your Blood Sugar Test Can Miss

Colorful plate of salmon and vegetables that supports healthy insulin and blood sugar balance

Prediabetes Isn't the First Warning Sign. Insulin Resistance Is.

You can have normal blood sugar and still have insulin resistance. Here's what your labs may not be telling you about your metabolic and heart health.

The short answer: Insulin resistance happens when your body's cells become less responsive to insulin, the hormone that helps regulate blood sugar. Your pancreas may compensate by producing more insulin, sometimes keeping glucose and A1c levels within normal ranges for years. This means insulin resistance can develop before prediabetes appears on routine blood tests. Recognizing your risk factors, evaluating your metabolic health, and making targeted lifestyle changes may help prevent or delay type 2 diabetes.

November is National Diabetes Month, and the numbers deserve our attention.

According to the Centers for Disease Control and Prevention (CDC), approximately 115.2 million American adults—more than 2 in 5—have prediabetes. About 8 in 10 don't know it.

But here's what I want my patients to understand: Prediabetes isn't necessarily where the problem begins.

In my functional medicine practice in Stamford, Connecticut, I work with patients who are concerned about stubborn weight gain, fatigue, cholesterol, blood pressure, and their long-term cardiovascular health. Some have been reassured that their blood sugar is normal, yet other metabolic risk factors deserve a closer look.

Your blood sugar is important. But it doesn't tell the entire metabolic story.

Can You Have Insulin Resistance With Normal Blood Sugar?

Yes. Insulin resistance can develop while fasting glucose and hemoglobin A1c remain within normal ranges. Your pancreas may initially compensate by releasing more insulin to help maintain healthy blood sugar levels.

Think of insulin as a key that helps glucose enter your cells, where it can be used for energy.

When your body becomes resistant to insulin, that key doesn't work as efficiently. Your pancreas responds by producing more insulin to get the job done.

For a while, this compensation may work.

Your fasting glucose looks normal. Your A1c looks normal. You may even feel perfectly fine.

But beneath the surface, your body may be working harder to maintain that balance.

Over time, insulin resistance can contribute to metabolic changes involving body fat distribution, triglycerides, blood pressure, and glucose regulation.

Eventually, some people develop prediabetes or type 2 diabetes. Others may have insulin resistance without progressing to diabetes.

The important takeaway? You don't have to wait for an abnormal A1c to start protecting your metabolic health.

What Are the Early Signs of Insulin Resistance?

One of the challenges with insulin resistance is that many people have no obvious symptoms.

However, certain physical findings, symptoms, and laboratory patterns may prompt a closer evaluation.

These include:

Increasing abdominal fat: Particularly weight gain around the waist, even without significant changes on the scale.
Fatigue or sluggishness after meals: Although nonspecific, persistent energy changes deserve attention.
Frequent hunger or cravings: Especially when accompanied by other metabolic risk factors.
Skin changes: Dark, velvety patches around the neck or underarms, known as acanthosis nigricans, can be associated with insulin resistance.
Elevated triglycerides or low HDL cholesterol: These findings may indicate underlying metabolic concerns.
Increasing blood pressure: Particularly when combined with abdominal weight gain or abnormal cholesterol.
Polycystic ovary syndrome (PCOS): A condition frequently associated with insulin resistance.

These findings do not automatically mean you have insulin resistance. Fatigue, cravings, and weight changes can have many causes, including thyroid disorders, sleep problems, medications, and hormonal transitions.

That's why a comprehensive evaluation matters more than any single symptom.

Who Is Most at Risk for Insulin Resistance?

Insulin resistance can affect people of different ages, body sizes, and backgrounds.

Your risk may be higher if you:

Have a parent or sibling with type 2 diabetes.
Carry excess weight around your abdomen.
Have a history of gestational diabetes.
Have PCOS.
Are physically inactive or spend much of your day sitting.
Have sleep apnea or chronically inadequate sleep.
Have high blood pressure, abnormal triglycerides, or metabolic dysfunction-associated steatotic liver disease (MASLD).
Are experiencing age-related changes in muscle mass and body composition.

Can Thin People Have Insulin Resistance?

Absolutely.

Being thin does not automatically mean someone is metabolically healthy.

Some people have relatively little excess body weight but still carry increased visceral fat, have low muscle mass, or develop unfavorable cholesterol and glucose patterns.

This is why I look beyond the number on the scale when evaluating metabolic and cardiovascular health.

The Menopause Connection: Why Insulin Resistance May Increase After 40

For women in perimenopause and menopause, metabolic changes can feel particularly frustrating.

You may be eating similarly to how you did in your 30s, yet your waistline is changing. Your cholesterol may be increasing, and maintaining muscle becomes more difficult.

What's happening?

Declining estrogen levels, aging, changes in body composition, disrupted sleep, and reduced physical activity can all influence metabolic health.

During the menopause transition, women may experience:

Increased abdominal and visceral fat.
Reduced lean muscle mass.
Changes in cholesterol levels.
Greater difficulty maintaining a healthy weight.
Changes in insulin sensitivity.

Not every woman develops insulin resistance during menopause, but this transition is an important time to reassess cardiovascular and metabolic risk.

In my practice, I evaluate factors such as thyroid function, sleep, nutrition, body composition, blood pressure, and cardiovascular markers to help women understand what may be contributing to their symptoms.

Menopause may change your metabolism, but it doesn't mean you have lost the ability to improve it.

Why Insulin Resistance Matters for Your Heart

This is where my background in cardiovascular medicine becomes especially important.

Insulin resistance is closely associated with metabolic syndrome, a cluster of risk factors that increases the likelihood of type 2 diabetes, heart disease, and stroke.

These risk factors include:

Increased waist circumference.
Elevated blood pressure.
High triglycerides.
Low HDL cholesterol.
Elevated fasting blood glucose.

A person is generally considered to have metabolic syndrome when at least three of these five criteria are present, using the appropriate clinical thresholds.

During my years working in cardiac surgery, I saw the consequences of cardiovascular disease firsthand.

That experience shaped how I approach prevention today.

I don't want patients to focus only on whether their blood sugar has crossed into the diabetic range. I want them to understand how their cholesterol, blood pressure, glucose regulation, body composition, and lifestyle factors work together.

Because protecting your metabolic health is also an important part of protecting your heart.

Related: Learn more about my approach to Heart Health.

How Do You Test for Insulin Resistance?

Recommended blood test that definitively diagnoses insulin resistance in everyday clinical practice.

Instead, I consider a patient's medical history, physical findings, risk factors, and laboratory results.

Depending on the individual, an evaluation may include:

1. Hemoglobin A1c

A1c estimates your average blood glucose over approximately the previous two to three months.

Common diagnostic ranges include:

Below 5.7%: Normal.
5.7%–6.4%: Prediabetes.
6.5% or higher: Diabetes range, generally requiring confirmation.

A normal A1c is reassuring, but it does not rule out insulin resistance.

2. Fasting Blood Glucose

This test measures blood sugar after a period without eating.

A fasting glucose of 100–125 mg/dL falls within the prediabetes range.

3. Fasting Insulin

Fasting insulin measures how much insulin is circulating in your bloodstream after fasting.

In selected patients, I may consider fasting insulin as an additional piece of information when evaluating metabolic health.

However, fasting insulin testing has limitations. Results vary between laboratories, and there is no universally accepted cutoff for diagnosing insulin resistance.

It should not replace established diabetes screening tests or be interpreted in isolation.

4. Lipid Panel and Advanced Cardiovascular Markers

Triglycerides, HDL cholesterol, LDL cholesterol, and other lipid measurements provide valuable information about cardiovascular risk.

An elevated triglyceride-to-HDL ratio can be associated with insulin resistance, although it is not a definitive diagnostic test.

Depending on your cardiovascular risk profile, additional testing such as ApoB or lipoprotein(a) may also be appropriate.

5. Blood Pressure and Waist Circumference

Sometimes the most useful clues aren't found in a blood test.

Blood pressure, abdominal fat distribution, family history, and changes in body composition can help identify patients who may benefit from a more comprehensive metabolic evaluation.

6. Oral Glucose Tolerance Test

In some circumstances, an oral glucose tolerance test may identify abnormal glucose regulation that is not apparent from fasting glucose or A1c alone.

7. Additional Functional Medicine Testing

The first six tests are widely available and can be ordered by any physician. Under the functional medicine model, Dr. Gengo may add additional testing to look deeper at how your body regulates blood sugar and insulin, helping uncover early metabolic changes that standard labs can miss.

The goal isn't to order every available test.

It's to choose the right tests for the right patient and interpret them together.

How Functional Medicine Approaches Insulin Resistance

Traditional medical screening plays an essential role in identifying prediabetes, diabetes, and cardiovascular risk.

Functional medicine can build on that foundation by taking a more comprehensive look at the factors influencing metabolic health.

Rather than focusing exclusively on a glucose number, I ask:

What is contributing to this patient's metabolic changes, and what can we do to improve their long-term health?

That may involve evaluating:

Nutrition: Are meals providing enough protein, fiber, and nutrient-dense foods? Are dietary patterns contributing to excess calorie intake or difficulty managing glucose?

Muscle mass and movement: Is the patient getting enough resistance exercise and daily physical activity?

Sleep: Could insufficient sleep or untreated sleep apnea be affecting metabolic health?

Hormonal and thyroid health: Are thyroid dysfunction, menopause-related changes, or PCOS contributing to the clinical picture?

Cardiovascular risk: What do blood pressure, cholesterol, family history, and other risk markers tell us?

Stress and daily routines: Are work schedules, chronic stress, or lifestyle demands making healthy habits difficult to maintain?

From there, we develop an individualized plan that may include nutrition changes, physical activity, sleep interventions, weight management, and medication when clinically appropriate.

Functional medicine should complement evidence-based medical care, not replace it.

Can Insulin Resistance Be Reversed?

Insulin sensitivity can often improve significantly through lifestyle changes, weight management when appropriate, and medical treatment.

And you don't need to overhaul your entire life overnight.

Here are five strategies I frequently encourage patients to consider.

1. Build Meals Around Protein and Fiber

Protein-rich foods and high-fiber carbohydrates can support fullness, balanced nutrition, and better post-meal glucose responses.

Try including:

Fish, chicken, eggs, tofu, or beans.
Leafy greens and colorful vegetables.
Lentils, chickpeas, and other legumes.
Berries and whole fruits.
Nuts, seeds, and healthy fats.

You don't have to eliminate every carbohydrate. The type, portion, and combination of foods matter.

2. Walk After Meals

A short walk after eating can help your muscles use glucose.

Start with 10–15 minutes after a meal when possible.

Even brief movement is better than remaining seated for hours.

3. Build and Maintain Muscle

Muscle is one of your body's major sites for glucose uptake.

Resistance training helps preserve muscle mass and can improve insulin sensitivity.

Aim for strength-building activities at least twice weekly, adjusted to your fitness level and medical needs.

This becomes especially important as we age.

4. Make Sleep a Metabolic Priority

Consistently poor sleep is associated with impaired glucose regulation and increased metabolic risk.

Most adults should aim for seven to nine hours of sleep per night.

If you snore, wake frequently, or feel exhausted despite adequate time in bed, it may be worth discussing sleep apnea with your healthcare provider.

5. Focus on Sustainable Changes, Not Extreme Dieting

For patients with overweight or obesity, even modest weight loss can make a meaningful difference.

The landmark Diabetes Prevention Program demonstrated that an intensive lifestyle intervention targeting approximately 7% weight loss and 150 minutes of weekly physical activity reduced the incidence of type 2 diabetes by 58% in high-risk adults over about three years.

You don't need perfection.

You need a plan you can realistically maintain.

What Should You Eat if You Have Insulin Resistance?

You may be surprised by how satisfying an insulin-conscious eating pattern can be.

Here's an example of a balanced day.

Breakfast: Scrambled eggs with spinach and peppers, avocado, and fresh berries.

Lunch: Grilled salmon or chicken over mixed greens with chickpeas, cucumbers, tomatoes, pumpkin seeds, and olive oil dressing.

Afternoon snack: An apple with almond butter or plain Greek yogurt with walnuts.

Dinner: Roasted fish or chicken, non-starchy vegetables, and a serving of lentils or sweet potato.

After dinner: A relaxed 10-minute walk.

Notice what we're adding: vegetables, fiber, quality protein, healthy fats, and movement.

This isn't about deprivation. It's about giving your body the nutrients and daily habits that support metabolic health.

Individual needs vary, especially for patients taking glucose-lowering medications or managing other medical conditions.

How Long Does It Take to Improve Insulin Resistance?

The timeline depends on your starting point, medical history, and consistency with lifestyle changes.

Some people notice improvements in energy, meal satisfaction, or daily well-being within several weeks.

Changes in blood pressure, glucose regulation, body composition, and cholesterol may take longer.

When appropriate, reassessing relevant laboratory markers after approximately three months can help evaluate progress. A1c is particularly useful because it reflects average glucose over roughly two to three months.

However, not everyone needs repeat fasting insulin testing, and improvement should be evaluated using the most clinically meaningful measures.

Remember, the goal isn't simply to lower one laboratory number.

The goal is to reduce long-term metabolic and cardiovascular risk.

Frequently Asked Questions About Insulin Resistance

Can you have insulin resistance with a normal A1c?

Yes. Your body may compensate for reduced insulin sensitivity by producing more insulin, keeping blood glucose and A1c within normal ranges. A normal A1c does not necessarily exclude insulin resistance.

What are the first warning signs of insulin resistance?

Many people have no symptoms. Possible clues include increased abdominal fat, acanthosis nigricans, elevated triglycerides, low HDL cholesterol, high blood pressure, or PCOS. These findings warrant evaluation but do not confirm a diagnosis.

Does insulin resistance cause belly fat?

Insulin resistance and excess abdominal fat are closely connected and can influence each other. However, abdominal weight gain can also result from aging, menopause, genetics, medications, and lifestyle factors.

What is the best test for insulin resistance?

There is no single routinely recommended clinical test that definitively diagnoses insulin resistance. Healthcare professionals assess metabolic risk using medical history, physical findings, glucose testing, A1c, lipid levels, and other appropriate measures. Fasting insulin may offer additional context in selected situations.

Can insulin resistance improve without medication?

Yes. Many people improve insulin sensitivity through physical activity, nutrition, adequate sleep, and weight management when appropriate. Others may benefit from medication based on their overall health and risk factors.

Is insulin resistance more common during menopause?

Changes in estrogen, abdominal fat distribution, muscle mass, sleep, and aging can influence insulin sensitivity during the menopause transition. However, menopause does not automatically cause insulin resistance in every woman.

Is insulin resistance the same as prediabetes?

No. Insulin resistance describes how the body responds to insulin. Prediabetes describes blood glucose levels that are above normal but below the diagnostic threshold for diabetes. Insulin resistance can occur before prediabetes, but the two conditions are not interchangeable.

Where can I get a metabolic health evaluation in Stamford, CT?

Dr. Lisa Gengo provides functional medicine and cardiovascular-focused evaluations in Stamford, Connecticut, serving patients from Greenwich, Norwalk, Westport, and surrounding Fairfield County communities. Evaluations may include metabolic risk factors, cholesterol, blood pressure, thyroid function, lifestyle, and appropriate laboratory testing.

Don't Wait for Your Blood Sugar to Become Abnormal

Here's what I want you to remember this National Diabetes Month:

A normal blood sugar result is valuable information, but it isn't the only measure of your metabolic health.

If you're experiencing unexplained weight changes, rising cholesterol, elevated blood pressure, or have a family history of type 2 diabetes, it may be time to look more closely at your overall risk.

My approach combines cardiovascular experience with functional medicine to help patients understand the bigger picture and make informed decisions about their health.

You don't have to wait for a diagnosis to start taking prevention seriously.

Ready to Take a Closer Look at Your Metabolic Health?

Call 203-434-9143 to schedule a discovery call with Dr. Lisa Gengo in Stamford, CT.

Serving Stamford, Greenwich, Norwalk, Westport, and surrounding Fairfield County communities.