Can You Have Insulin Resistance With Normal Blood Sugar? 6 Labs to Check

Did you know that you can have a normal fasting glucose or a normal A1c and still have a problem managing blood sugar? Medicine is ruled by cut-offs. We need them for diagnosis, for billing, for medication choices, for tracking over time. The American Diabetes Association has created definitions for insulin resistance in a variety of ways:

• Prediabetes
  • Fasting glucose 100-125 mg/dL (on two separate occasions)
  • A1c 5.7%-6.4%
• Diabetes
  • Fasting glucose >126 mg/dL (on two separate occasions)
  • A1c >6.5%

These cut-offs are not arbitrary but rather serve to capture individuals at high risk of disease or progression of disease. We have clear data that being above these cut-offs is correlated with a variety of health risks. But insulin resistance, a metabolic problem that has clear correlations to future health risks, is present at values below these cut offs.

In order to pursue health, having a healthy metabolism is one of the most important factors. So I want to go through the data I find the most helpful when assessing a patient’s metabolic health and risk of insulin resistance.

Can You Have Insulin Resistance With Normal Blood Sugar?

Yes. Normal fasting glucose and A1c do not necessarily mean that your body is responding normally to insulin. Insulin resistance can develop before blood glucose rises into the prediabetes or diabetes range.

This is one reason looking at multiple metabolic health markers can provide a more complete picture than relying on glucose or A1c alone.

What Is Insulin Resistance?

Our bodies exist in two states: fed or fasted. Insulin is one of the main regulators that orchestrates how the body responds in these two states.

In a normal fasted state:

1. Insulin levels are low.
2. The liver increases glucose production (this is why your blood sugar never reaches 0, no matter how long you fast).
3. Fat breaks down to supply a fuel substrate for the body.

In a fed state, however, insulin increases to do 3 things:

1. Push incoming glucose from the blood into tissues like muscle for usage or storage.
2. Turn off the liver’s production of glucose.
3. Turn off the breakdown of fat.

When energy intake chronically exceeds the body’s natural metabolism, it loses its ability to safely manage and store energy. Fat starts being stored within tissues like the liver and muscle. This type of fat, also called “ectopic fat,” can be harmful: it increases oxidative stress, generates inflammatory signaling, and breaks down proper insulin signaling.

Once insulin signaling breaks down, the body can no longer properly regulate its energy balance. The pancreas compensates by producing progressively more insulin, trying to force-correct these metabolic processes; but unless identified and intentionally corrected, this becomes a worsening, chronic problem.

Insulin Resistance Is a Spectrum

The first thing to understand is that diagnostic thresholds do not easily define biology. Insulin resistance is a spectrum, with clear normal and high values but also a very wide area of grey. Though you can treat and even reverse insulin resistance in many cases, it’s in this grey that we have the best chance at improving healthspan.

Our bodies are complex, intricate, and integrated systems; so glucose metabolism cannot be summed up and monitored with just one or two data points. We need to look at values across different organ systems to truly define and track the problem over time. We need to see patterns in the data, not just look for highs or lows.

I want to go through my top 5 ways to assess insulin resistance:

1. Glucose and A1c
2. Fasting insulin
3. Triglycerides and HDL-C
4. ALT
5. Uric Acid
6. HOMA-IR (Bonus!)

1. Glucose and Hemoglobin A1c: The Basic Insulin Resistance Tests

Obviously, we have to start here first. As I mentioned above, a fasting glucose and/or Hemoglobin A1c are used in the definition of prediabetes and diabetes. If either of these numbers fall into the prediabetes or diabetes range on your blood work, we have a problem that needs fixing.

I do want to highlight a pattern I routinely see: a normal fasting glucose with an A1c in the prediabetes range of 5.7%-5.9%. This pattern may highlight a phenomenon called glucose intolerance.

Since A1c is a roughly 3-month average of glucose levels, it takes into account fasting and post-meal blood sugars. With glucose intolerance, your insulin does not respond quickly enough at meals, causing very high post-meal blood sugars; but after a few hours, it is able to catch up and bring glucose down into more appropriate ranges.

If you see this pattern on your blood work, a continuous glucose monitor (CGM) can be a reasonable next step to better evaluate if you are having higher-than-expected glucose spikes with meals.

2. Fasting Insulin: An Early Sign of Insulin Resistance

Fasting insulin is a great metric that partners well with a fasting glucose. It tells us how much work your pancreas is doing to keep blood sugars in check.

An elevated fasting insulin with a normal glucose value can be a very early warning sign of insulin resistance and often presents in lab work years before someone develops overt prediabetes or diabetes.

In our practice, we recommend a fasting insulin level to be <10 µIU/mL. Anything above that, especially consistently above this range, suggests early insulin resistance and should be addressed with lifestyle changes.

Of note, the lab assay for insulin is not standardized, so it can vary lab-to-lab. Therefore, you will want to repeat an elevated insulin level using the same lab company when trending it over time.

3. Triglycerides and HDL-C: What Your Cholesterol Can Tell You About Metabolic Health

If you watched our last video on cholesterol, this will sound familiar. Triglycerides are measured as part of the standard lipid panel and give us information on energy balance.

Elevated triglycerides often reflect an oversupply of circulating energy, particularly when the liver is producing and exporting more fat than usual. This contributes to increased circulating cholesterol particles as well as accelerated body fat gain.

HDL-C, when low, has been correlated with metabolic syndrome — a condition where insulin resistance is a major factor. Metabolic syndrome is associated with the progression of many chronic medical conditions, like diabetes, heart disease, and strokes.

For triglycerides (TG), we recommend aiming for <100 mg/dL.

For HDL-C, we like to see your values >40 mg/dL in men and >50 mg/dL in women.

You can also do a TG ratio, dividing triglycerides by HDL-C. A normal cut off is <2 while optimal cut off is <1.

4. ALT and Liver Health: Another Clue to Insulin Resistance

ALT is a liver enzyme that is leaked into the bloodstream during liver injury. Though there are many reasons for liver injury, a major one that relates to insulin resistance is fatty liver (now called metabolic dysfunction-associated steatotic liver disease — great name, right??).

This fat deposition is the ectopic fat I described above, damaging the liver and interfering with its ability to properly respond to insulin.

Though your lab may state an ALT is normal in the 40s or 50s, any value over 30 U/L is suspicious for early fat deposition in the liver and should be monitored closely, especially if we see other signs of metabolic dysfunction in lab work.

Interestingly, the high cut-off reference range for ALT is often in the upper 40s or 50s. Many liver specialists believe this is too high of a cut-off for truly identifying liver injury.

This is a good example of a statement I commonly make to patients: “Normal labs does not mean normal health.”

My preference is to have an ALT <30 U/L.

5. Uric Acid: An Overlooked Marker of Metabolic Health

Commonly thought of as the gout marker, uric acid is the final product of purine metabolism. Fructose metabolism can also increase uric acid production.

Though not perfect, I use uric acid as another supporting clue for possible insulin resistance and opportunities to improve a patient’s diet. Elevated values often track with insulin resistance and can also prompt me to look more closely at fructose intake, alcohol, kidney function, medications, and other contributors.

I like to have patients maintain a uric acid <7 mg/dL, and <6 mg/dL if you have a history of gout.

6. HOMA-IR: A Useful Calculation for Insulin Resistance

HOMA-IR stands for Homeostatic Model Assessment of Insulin Resistance. It is a simple calculation that combines your fasting glucose and fasting insulin into one number.

The formula is:

HOMA-IR = fasting glucose (mg/dL) × fasting insulin (µIU/mL) ÷ 405

HOMA-IR tells us how much insulin your body needs to maintain your fasting blood sugar. There is no universally accepted cutoff for HOMA-IR, partly because insulin testing is not perfectly standardized between labs.

In our practice, I generally like to see a HOMA-IR around 2 or lower. Once values are consistently above 2, I become more suspicious that insulin resistance is present, especially if other markers like triglycerides, HDL-C, ALT, or uric acid are also moving in the wrong direction.

What Blood Tests Should You Check for Insulin Resistance?

If you are trying to understand your metabolic health, looking at a combination of markers can be much more informative than looking at fasting glucose alone.

The six markers I find most helpful are:

• Fasting glucose and A1c
• Fasting insulin
• Triglycerides and HDL-C
• ALT
• Uric acid
• HOMA-IR

The goal isn’t to focus on a single number. Instead, look for patterns across multiple markers and follow those markers over time.

Managing and Reversing Insulin Resistance

If you are worried about insulin resistance, know that you have prediabetes or diabetes, or simply want to improve your metabolic health, the goal is to follow these markers over time rather than focus on a single lab value.

Most of these tests are inexpensive and commonly included in routine blood work. Together they can give you a much better picture of how efficiently your body is managing energy.

Insulin resistance exists on a spectrum, so improvement often shows up as several markers gradually moving in the right direction rather than one number suddenly becoming “normal.”

The encouraging part is that insulin resistance is often highly responsive to changes in nutrition, exercise, body composition, sleep, and, when needed, medication. Improving these numbers is not just about avoiding diabetes; it is about improving the way your body handles energy and reducing the long-term risks associated with poor metabolic health.

For patients in Asheville, NC, and Greenville, SC, understanding these metabolic markers can be an important part of taking a more proactive approach to long-term health. If your routine blood work looks “normal” but you have concerns about energy balance, weight, blood sugar, or metabolic health, talk with your healthcare provider about whether additional testing may be appropriate for you.