Deep Dives › Metabolic Health and Diabetes
Fasting insulin: what it tells you, and when it lies
How to read a fasting insulin and a HOMA-IR properly: the units that make results absurd, what the arithmetic actually means, why the thresholds are conventions rather than cutoffs, the four traps that make an accurate value mislead, and the honest limits of what follows from a raised result.
Reviewed by Team SOMA
Last updated September 2026 · English
What you'll be able to do
- âś“The units that make a result look absurd, and how to convert without guessing
- âś“What the HOMA-IR arithmetic is actually doing, and what it assumes
- âś“Why the familiar thresholds are conventions, and what follows from that
- âś“The four traps that make an accurate value mislead
- âś“What does and does not follow from a raised result
What's inside
Before you read
The deep reading
Reading fasting insulin: interpretation, traps and decisions
The case
The case, and your decision
Check yourself
Check yourself: fasting insulin and HOMA-IR
In practice
In practice this week
Is this for you?
Who it's for
- Anyone with a result in hand who wants the reasoning, not only the conclusion
- People with no medical training - every technical term is explained the moment it appears
- Practitioners who want the thinking behind a number rather than a protocol
What you need
- No prior training. Every technical term is explained in plain words the first time it appears.
- A willingness to read something twice.
About this Deep Dive
A fasting insulin is one of the few cheap tests that describes the work being done to keep another number normal. It is also one of the easiest to misread: the units differ between laboratories, the arithmetic behind HOMA-IR is rarely stated, and the thresholds in common use are conventions rather than cutoffs.
What this covers
- The units that make a result look absurd, and how to convert without guessing
- What the HOMA-IR arithmetic is actually doing, and what it assumes
- Why the familiar thresholds are conventions, and what follows from that
- The four traps that make an accurate value mislead
- What does and does not follow from a raised result
How it is built
Five parts, taken in order: a prediction you commit to before reading anything, the reading itself, one worked case with a decision to make, a check to see whether it landed, and a page on what changes once you have it. About forty minutes, and it is written to be read twice. There is no certificate here — that is what the Certified Programmes are for.
Who wrote it
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