06/10/2026
WHY DON’T WE TEST FASTING INSULIN?
Your blood sugar can look “normal” while your metabolism is already in trouble.
This is one of the biggest blind spots in conventional metabolic screening.
Most routine check-ups focus on fasting glucose and HbA1c.
Those tests are useful.
But they primarily tell us what your glucose has been doing.
They don't necessarily tell us how hard your pancreas is working to keep that glucose normal.
HERE’S THE PROBLEM 👇
Imagine two people who both have a fasting glucose of 90 mg/dL (5.0 mmol/L).
On paper, they look identical.
But suppose:
Person A:
Fasting insulin = 4 µIU/mL
Person B:
Fasting insulin = 20 µIU/mL
Both have “normal” glucose.
But the second person's pancreas may be producing substantially more insulin to maintain that normal glucose.
That can be an early clue that insulin resistance is developing.
And this is where metabolic dysfunction can hide for years.
INSULIN RESISTANCE CAN COME FIRST
In the early stages, the body can compensate for insulin resistance by producing more insulin.
Glucose may remain normal.
HbA1c may remain normal.
The patient may feel completely well.
The routine blood test comes back:
“Everything looks fine.”
But metabolically, things may already be changing.
Over time, compensation can become less effective.
Then we may start seeing:
• Rising fasting glucose
• Rising HbA1c
• Prediabetes
• Type 2 diabetes
• Increasing visceral fat
• Fatty liver
• High triglycerides
• Low HDL
• Hypertension
• Metabolic syndrome
By the time glucose becomes consistently abnormal, the metabolic problem may have been developing for years.
SO WHY ISN’T FASTING INSULIN ROUTINELY TESTED?
There isn't one simple answer.
Fasting insulin has limitations.
Laboratory insulin assays aren't perfectly standardized, reference ranges vary, and there isn't a universally accepted fasting-insulin cutoff that diagnoses insulin resistance in every person.
That's important.
Fasting insulin is not a magic test.
But that doesn't mean it is useless.
In the appropriate clinical context, fasting insulin can provide additional information that fasting glucose and HbA1c alone may miss.
It becomes particularly interesting when interpreted alongside:
Fasting glucose + fasting insulin + triglycerides + HDL + waist circumference + blood pressure + HbA1c
And from fasting glucose and insulin, clinicians can calculate indices such as HOMA-IR.
THE BIGGER QUESTION IS:
Do we want to wait until glucose becomes abnormal before paying attention to insulin resistance?
Or do we want to identify metabolic dysfunction while there is still an opportunity to intervene?
Because prevention is not about waiting for the lab report to say:
“DIABETES.”
Prevention is about recognising the trajectory before the disease becomes established.
WHAT COULD EARLY IDENTIFICATION HELP US ADDRESS?
Depending on the individual's overall risk profile, early metabolic intervention may include:
🥩 Adequate protein
🥦 Minimally processed whole foods
🚫 Reducing excess refined carbohydrates and added sugars
🏋️ Resistance training and preservation of muscle mass
🚶 Regular physical activity
😴 Improving sleep
🧘 Managing chronic stress
⚖️ Reducing visceral adiposity where appropriate
🍺 Addressing excess alcohol intake
🩺 Monitoring blood pressure, triglycerides, HDL and liver health
The goal isn't simply to make a laboratory number look better.
The goal is to improve metabolic health before disease takes hold.
ONE IMPORTANT CAVEAT
A high fasting insulin result does not automatically mean someone has insulin resistance, and a low result does not automatically mean someone is metabolically healthy.
Insulin must be interpreted in context.
But here's the point:
If we only look at glucose, we can sometimes see the smoke before we look for the fire.
Your glucose may be normal.
Your HbA1c may be normal.
You may not have diabetes.
And yet your metabolism may already be working much harder than it should.
NORMAL GLUCOSE DOES NOT ALWAYS MEAN NORMAL METABOLISM.
Sometimes the most important question isn't:
“Is your blood sugar high?”
It's:
“How much insulin does your body need to keep your blood sugar normal?”
That is a very different question.
Test earlier. Think earlier. Intervene earlier.
— Dr Rian
Functional Medicine Doctor