What is an optimal fasting insulin level?
The short answer
An optimal fasting insulin level is 2–5 µIU/mL. Dr. Mark Hyman puts the ceiling at 5. You can watch him say it below.
Most labs call fasting insulin high only above 25. So your report can call 15 normal while it sits above where he draws the line.
“Her insulin normally should be under five fasting, and under like 25 or 30 after a drink.”
Where a number lands, and who said so
- under 2 µIU/mL Most labs flag this as low
- 2–5 µIU/mL The range Dr. Mark Hyman draws
- 5–25 µIU/mL Normal on most reports. Above optimal Dr. Mark Hyman · 23:23 →
- 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.
One of the doctors we cite, on why it matters
“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?
2–5 µIU/mL, according to Dr. Mark Hyman.
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?
Under 2 µIU/mL, your report marks it low. Between 2 and 25 it prints as normal. Over 25, your report marks it high. Where the people we follow draw their own line is above.
Is fasting insulin of 15 normal?
Your lab will call it normal. Dr. Mark Hyman puts the ceiling at 5 µIU/mL, so by that number it is high.
Do they all agree?
No. Dr. Peter Attia puts the line somewhere else: “the fasting insulin below six.”
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.
Where does this number come from?
Dr. Mark Hyman, on video. The link above jumps straight to that minute.
They don't all draw the line in the same place
“the fasting insulin below six.”
“if certain blood biomarkers are in the normal range, so a fasting insulin under six, an HbA1c maybe under 5.4, even under 5.2.”