The fasting glucose–insulin connection.
Two laboratory values describe part of a feedback loop.
Why paired fasting measurements?
HOMA interprets basal glucose and insulin together. It simplifies a biological system into a model; it does not recreate the dynamic response to a meal or glucose challenge.
Where C-peptide fits
C-peptide is released during insulin production, but its concentration is affected by different clearance processes. It is a useful laboratory marker with its own interpretation and units.
What a fasting index leaves out
A fasting estimate does not directly observe post-meal insulin responses or measure glucose disposal during a clamp experiment. The right assessment depends on the clinical or research question.
Matthews et al. · HOMA, 1985 (opens in a new tab) · Mayo Clinic Laboratories · C-peptide (opens in a new tab) · Katz et al. · QUICKI, 2000 (opens in a new tab)