What Labs Should You Get to Evaluate Risk for High A1C, Diabetes, and Hyperinsulinemia?
Millions of people walk around each day with elevated blood sugar and insulin levels—completely unaware. Often, by the time prediabetes is diagnosed, the body has already been struggling with insulin resistance and hyperinsulinemia for years. The good news? You can get ahead of the curve with the right lab tests.
Whether you're managing your weight, concerned about metabolic health, or noticing signs like fatigue, stubborn belly fat, or sugar cravings, early lab testing can provide a powerful window into your body’s metabolic function.
This article walks you through the core lab tests that help assess your risk for high A1C, diabetes (both prediabetes and Type 2), and elevated insulin levels (hyperinsulinemia). Understanding these numbers could be the first step toward reclaiming your health.
Why These Labs Matter
When it comes to blood sugar problems, prevention and early detection are critical. According to the CDC, over 96 million American adults have prediabetes—and more than 80% of them don’t know it. Even more concerning is that many of these individuals have hyperinsulinemia (chronically high insulin) for years before blood sugar changes show up on routine tests.
Unfortunately, most standard annual check-ups only include fasting glucose and sometimes an A1C. These markers alone don’t tell the full story.
The following labs offer a broader, more proactive approach to evaluating insulin resistance, blood sugar control, and your overall metabolic health.
1. Hemoglobin A1C (HbA1c)
What it is:
HbA1c measures the percentage of hemoglobin (a protein in red blood cells) that is "glycated," or bound to sugar. It reflects your average blood glucose over the past 2–3 months.
Why it matters:
This test is commonly used to diagnose prediabetes and Type 2 diabetes. While it's a useful long-term marker, it can be misleading in people with anemia, low iron, or certain blood disorders.
Key Ranges:
- Normal: Below 5.7%
- Prediabetes: 5.7% – 6.4%
- Diabetes: 6.5% and above
2. Fasting Insulin
What it is:
This measures the amount of insulin in your blood after 8–12 hours of fasting. It helps evaluate how hard your pancreas is working to maintain normal blood glucose levels.
Why it matters:
Fasting insulin is one of the earliest indicators of insulin resistance, often rising years before A1C or glucose levels become abnormal.
High fasting insulin = your body is pumping out more insulin to overcome cellular resistance. This is a key sign of hyperinsulinemia, which drives fat storage, cravings, energy crashes, and eventually diabetes.
Optimal Range:
- Optimal: 2–6 µIU/mL
- Early insulin resistance: 7–15 µIU/mL
- Hyperinsulinemia: >15 µIU/mL
3. Fasting Blood Glucose (FBG)
What it is:
This is the most common and familiar blood sugar test. It measures the concentration of glucose in your blood after fasting overnight.
Why it matters:
While simple and widely available, fasting glucose often remains normal for years—even in people with worsening insulin resistance.
Still, it’s a useful piece of the puzzle and a baseline to compare with insulin and A1C.
Key Ranges:
- Normal: <100 mg/dL
- Prediabetes: 100–125 mg/dL
- Diabetes: 126+ mg/dL
4. Oral Glucose Tolerance Test (OGTT) with Insulin
What it is:
This test measures how your body responds to a large glucose load (usually 75g), with glucose and insulin levels checked at baseline and several intervals (30, 60, 90, and 120 minutes).
Why it matters:
The OGTT gives insight into both glucose clearance and insulin response—two key components of metabolic health.
By adding insulin readings alongside glucose, you can detect early-stage insulin resistance that might otherwise go undiagnosed.
Red Flags:
- Glucose levels that stay elevated longer than 2 hours
- Excessively high insulin spikes at 30 or 60 minutes
- Failure of insulin to drop back to baseline by 120 minutes
5. C-Peptide
What it is:
C-peptide is a byproduct of insulin production. It reflects how much insulin your pancreas is producing.
Why it matters:
While insulin itself is sometimes variable due to external insulin therapy or clearance rate, C-peptide can provide a more stable view of endogenous insulin output.
Ideal Range:
- Typically 0.5–2.0 ng/mL (varies slightly by lab)
6. Lipid Panel (Cholesterol & Triglycerides)
What it is:
A standard lipid panel measures total cholesterol, HDL, LDL, and triglycerides.
Why it matters:
While not a direct measure of insulin, lipid patterns can hint at insulin resistance.
Key markers to watch:
- High triglycerides (>150 mg/dL)
- Low HDL (<40 mg/dL men, <50 mg/dL women)
- Triglyceride:HDL ratio >2.0 → strong predictor of insulin resistance
7. High-Sensitivity C-Reactive Protein (hs-CRP)
What it is:
hs-CRP is a blood marker of systemic inflammation.
Why it matters:
Chronic inflammation is both a cause and effect of insulin resistance. Elevated hs-CRP is associated with obesity, poor diet, cardiovascular risk, and progression to Type 2 diabetes.
Optimal Range:
- Ideal: <1.0 mg/L
- Moderate risk: 1.0–3.0 mg/L
- High risk: >3.0 mg/L
Summary: The Big Picture
| Test | What it Measures | Why it Matters |
| HbA1c | Avg. glucose over 3 months | Diagnoses prediabetes & diabetes |
| Fasting Insulin | Insulin levels in fasting state | Early marker for insulin resistance |
| Fasting Glucose | Glucose at fasting baseline | Easy to monitor; confirms diabetes |
| OGTT with Insulin | Glucose & insulin after glucose load | Deep insight into metabolic function |
| C-Peptide | Internal insulin production | Evaluates beta-cell function |
| Lipid Panel | Triglycerides, HDL, LDL | Patterns show insulin resistance |
| hs-CRP | Inflammation level | Tied to metabolic and cardiovascular risk |
What to Do Next
If you're concerned about blood sugar, weight gain, or insulin resistance, don’t wait until your A1C is “too high.” Ask your doctor or functional practitioner to run a complete metabolic panel that includes fasting insulin and C-peptide, not just glucose.
Pro Tip: Combine fasting glucose with fasting insulin to calculate your HOMA-IR (Homeostatic Model Assessment of Insulin Resistance). A value above 1.5 may indicate early insulin resistance. Tools like this online calculator can help.
When to Get Tested
Consider testing from your own provider if you:
- Have a family history of diabetes or heart disease
- Struggle with weight, cravings, or belly fat
- Experience fatigue after meals or frequent hunger
- Have PCOS, fatty liver, or high blood pressure
- Follow a high-carb or processed food diet
- Want to start a preventive low-carb or keto plan
Final Thoughts
Lab testing empowers you to take charge of your metabolic health—long before chronic disease develops. With the right information, you can make targeted changes in your diet, movement, and lifestyle that move the needle toward optimal health.
Don’t rely on guesswork. Know your numbers, discuss them with your provider, and use them to make informed decisions—because prevention always beats treatment.
For more information about lab tests, reference ranges, and risk considerations, check out Common Sense Labs by Dr. Ken D Berry and Kim Howerton.
References
- Centers for Disease Control and Prevention. Prediabetes: Your Chance to Prevent Type 2 Diabetes
- Kraft, J. (2008). Diabetes Epidemic & You. Self-published.
- American Diabetes Association. Standards of Medical Care in Diabetes—2024
- Dr. Joseph Kraft (Insulin Assay OGTT Pioneer). Hyperinsulinemia diagnosis research
- The Blood Code. HOMA-IR Calculator
- Mayo Clinic. C-peptide Test
- Cleveland HeartLab. The role of hs-CRP in predicting heart disease