Y Is for Your Labs, Your Language: Interpreting A1c, Fasting Insulin, and Glucose Like a Pro
Micro Habit: Ask your doctor for a fasting insulin test if you haven’t had one.
You go in for your annual checkup. The doctor scans your labs and smiles: “Everything looks fine, your glucose is normal.” You exhale, relieved.
But there’s a quiet problem. The most important number for detecting early insulin resistance wasn’t even tested.
That missing lab? Fasting insulin.
It’s the first signal that your metabolism is struggling, years before glucose or A1c rise high enough to flag a problem.
Why glucose and A1c don’t tell the whole story
Glucose is the number everyone recognizes because it’s easy to measure and directly tied to diabetes diagnosis. But glucose tells you what’s happening in the moment, not what’s been brewing behind the scenes.
A1c is the long-term average, a 3-month reflection of blood sugar exposure. It’s a helpful summary, but it only changes after glucose has been elevated for a long time.
By the time either of these numbers climb, insulin resistance has often been present for five to ten years.
Insulin resistance starts quietly. Your pancreas works overtime, releasing more insulin to keep blood sugar normal. You don’t feel it, and your labs still look “fine.” But that high insulin is your early warning, the canary in the metabolic coal mine.
The lab that changes everything
A fasting insulin test reveals how hard your body is working to keep glucose in range. When insulin levels are elevated, it’s a sign your cells are starting to ignore its signal.
Here’s what the pattern looks like:
Stage 1: Insulin rises, glucose still normal.
Stage 2: Insulin stays high, glucose begins to climb.
Stage 3: Both insulin and glucose are high, now it’s prediabetes or diabetes.
Most people only catch the problem at stage 3, when it’s harder to reverse.
That’s why pairing fasting glucose with fasting insulin gives a much clearer picture. From these two numbers, you can calculate your HOMA-IR (Homeostatic Model Assessment of Insulin Resistance), a simple formula that estimates how resistant your body is to insulin.
It’s one of the most powerful yet underused tools in preventive medicine.
How to understand your results
Here’s a simplified way to think about your labs:
A typical healthy fasting insulin level is below 8 μIU/mL, though optimal levels are often closer to 5 or less. A HOMA-IR under 1.5 suggests good insulin sensitivity, while values above 2.0 can indicate early resistance.
It’s not just numbers, it’s a metabolic language. Once you understand it, you can read what your body’s been whispering long before it starts shouting.
Quick example: how to calculate your HOMA-IR
You can calculate HOMA-IR using a simple formula:
HOMA-IR = (Fasting Insulin × Fasting Glucose) ÷ 405
This version is used when glucose is in mg/dL (the U.S. standard).
Example (U.S.):
Fasting insulin = 10 μIU/mL
Fasting glucose = 95 mg/dL
→ (10 × 95) ÷ 405 = 2.35
That HOMA-IR of 2.35 suggests early insulin resistance.
If your lab reports glucose in mmol/L (used internationally), use:
HOMA-IR = (Fasting Insulin × Fasting Glucose) ÷ 22.5
Example (International):
Fasting insulin = 10 μIU/mL
Fasting glucose = 5.3 mmol/L
→ (10 × 5.3) ÷ 22.5 = 2.36
Different units, same insight, the higher the HOMA-IR, the more your body is working to keep glucose stable.
Why this matters so much
High insulin doesn’t just affect blood sugar, it drives fat storage, hunger, and inflammation. It’s linked to conditions like high triglycerides, hypertension, PCOS, and even Alzheimer’s disease.
Think of insulin as your body’s traffic director. When the signals get jammed, glucose and fat both back up in the bloodstream, slowing everything down.
Catching insulin resistance early gives you time to intervene, with habits, not prescriptions.
Micro Habit: Ask for a Fasting Insulin Test
Why it helps: You can’t improve what you don’t measure. Asking for this test gives you insight into how your metabolism is working today, not years after symptoms appear.
How to do it:
At your next appointment, ask for a fasting insulin alongside your glucose and A1c.
Write down all three numbers when your labs come back.
Use a free online calculator or the formula above to estimate your HOMA-IR.
If your insulin or HOMA-IR is high, talk with your doctor about lifestyle changes, especially around nutrition, movement, and sleep.
It’s a small habit that could change the trajectory of your health.
Let’s Reframe Your Labs
Your labs aren’t just data points, they’re a conversation between your habits and your hormones. Once you learn to read that conversation, you stop guessing.
Start with one test. Start with “Y.” Because the earlier you understand your body’s language, the easier it is to translate it back into health.
You’re just one healing habit away.
Coming Up Next:
Z – Zeroing In on One Habit: How to personalize your diabetes reversal journey.
Just in case you missed last week’s:
X Is for Xenoestrogens and Endocrine Disruptors: Environmental Toxins and Glucose. Read it here.
Want to Go Deeper?
If today’s post helped you understand your labs in a new way, you’ll love what we’re exploring inside The Habit Healers.
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Story-driven science that explains complex ideas clearly
Practical tools and trackers to retrain your metabolism
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Subscribe now to join The Habit Healers. Because healing your metabolism isn’t about restriction. It’s about restoring trust in your body.
You’re just one healing habit away.
Y Is for Your Labs, Your Language: Interpreting A1c, Fasting Insulin, and Glucose Like a Pro
Micro Habit: Ask your doctor for a fasting insulin test if you haven’t had one.
Section 1: What You Learned
Reflect on the ideas from the article to make this habit more meaningful.
Have you ever had a fasting insulin test before? If not, what might have been missed?
Which number do you usually pay attention to—glucose, A1c, or both?
What surprised you about the difference between glucose, A1c, and insulin?
Section 2: Your Micro Habit Plan
Goal: Ask your healthcare provider for a fasting insulin test to pair with your glucose and A1c, then use your results to calculate your HOMA-IR score.
This week I will:
☐ Ask for a fasting insulin test at my next appointment
☐ Write down my fasting insulin, glucose, and A1c results
☐ Calculate my HOMA-IR score (see below)
☐ Review my numbers with my healthcare provider
☐ Identify one lifestyle habit to improve insulin sensitivity
☐ Other: ____________________________________________
Section 3: How to Calculate Your HOMA-IR
If your glucose is in mg/dL (U.S. labs):
HOMA-IR = (Fasting Insulin × Fasting Glucose) ÷ 405
If your glucose is in mmol/L (international labs):
HOMA-IR = (Fasting Insulin × Fasting Glucose) ÷ 22.5
Example (U.S.):
Insulin = 10 μIU/mL, Glucose = 95 mg/dL → (10 × 95) ÷ 405 = 2.35
Example (International):
Insulin = 10 μIU/mL, Glucose = 5.3 mmol/L → (10 × 5.3) ÷ 22.5 = 2.36
Section 4: Reflection Prompts
What did your results tell you about how your metabolism is working?
How did your fasting insulin compare to your glucose or A1c?
What small changes could help lower your insulin or HOMA-IR score?
How does tracking insulin make you feel more proactive about your health?
Section 5: Small Wins Tracker
Each small action builds momentum. Track your wins below.
useful; like most I get just fasting glucose and A1C. These are creeping up so I think fasting insulin must be also but more data is good
Interesting information. My Fasting Insulin level is 2.9 (in optimal range), but my Hemoglobin A1c is 5.7, which is considered high/pre diabetes. How can both be true? I calculated my HOMA-IR to be .6516, so it appears my pancreas is doing its job.
As always...thanks for good, clear information.