What is an optimal fasting insulin level?
The short answer
In the clips below, optimal fasting insulin is under 5 µIU/mL.
Most labs call fasting insulin high only above 25. So your report can call 15 normal while it sits above the optimal ceiling.
Sources disagree on optimal
“yet the ideal insulin should be under five not 15”
“the insulin reference range they have is 18 as normal, and anything above that is abnormal and anything below is normal. It should be five or less.”
“So we'd like to know what your fasting insulin is, and optimally, it would be less than five”
Not every source agrees with that line.
“the fasting insulin below six.”
What each range means
- under 5 µIU/mL Optimal
- 5–25 µIU/mL Normal on most reports. Above optimal“the insulin reference range they have is 18 as normal, and anything above that is abnormal and anything below is normal. It should be five or less.” Dr. Mark Hyman · 19:59 →
- over 25 µIU/mL Most labs flag this as high
What fasting insulin measures
How much insulin your pancreas is releasing at rest.
Insulin climbs to hold glucose steady long before glucose itself moves. So it can show strain years earlier.
Checked against MedlinePlus — Insulin in Blood.
Why it matters, on the record
“the more we only look at glucose, we're waiting for the late marker because insulin resistance in its earliest form before it's type 2 diabetes is a state of elevated insulin but normal glucose. And so if glucose is the clinical marker that we're focusing on, it's going to remain clinically silent or undiagnosed.”
Common questions
What is an optimal fasting insulin level?
Under 5 µIU/mL, from a quote on video (Dr. Mark Hyman, 8:52).
What is a normal fasting insulin level?
Most US labs print 2–25 µIU/mL. Your report grades you against that range. It exists to catch disease, not to describe your best.
What does your fasting insulin number mean?
On a typical lab range, under 2 µIU/mL is low, 2 to 25 is normal and over 25 is high. Your own report prints its range next to your number, and that is the one your lab uses. The optimal range on this page comes with the quote behind it.
Is fasting insulin of 15 normal?
A typical lab range calls it normal. On video, the optimal ceiling is 5 µIU/mL (Dr. Mark Hyman, 8:52), so by that line it is high. Not every source agrees with that line.
Do the sources agree?
No. There is also a case for a different line: “the fasting insulin below six.” (Dr. Peter Attia, 6:38)
What does the fasting insulin test measure?
How much insulin your pancreas is releasing at rest. Insulin climbs to hold glucose steady long before glucose itself moves. So it can show strain years earlier.