HOMA-IR

True fasting hypoglycemia is most often seen with diabetes treatment — excess insulin, sulfonylureas, or meglitinides.

A low glucose result can sometimes be false, especially if the blood sample was not processed quickly enough.

Other causes include alcohol intake especially without adequate food, prolonged fasting or malnutrition, critical illness or sepsis, liver, kidney, or severe heart failure, adrenal or pituitary insufficiency, insulin-secreting tumors (insulinoma), and some non-diabetes medications.

High fasting glucose (hyperglycemia) most commonly reflects prediabetes, insulin resistance, or diabetes (type 1, type 2, gestational).

Other causes: pancreatic damage (chronic pancreatitis, hemochromatosis), endocrine disorders that drive insulin resistance (Cushing syndrome, acromegaly, pheochromocytoma), acute physiologic stress or illness, and medications such as glucocorticoids, phenytoin, statins, and estrogens.

Decreased insulin in a lean, metabolically healthy person means the body needs very little insulin while fasting (very good insulin sensitivity), usually seen in athletes or those on a low carbohydrate diet.

Low fasting insulin reflects reduced pancreatic beta-cell output. Causes include type 1 diabetes (autoimmune beta-cell destruction), advanced type 2 diabetes with beta-cell exhaustion, LADA, pancreatic disease, and hypopituitarism.

Prolonged fasting (beyond the standard 12 hours) can also drive values very low.

High fasting insulin (hyperinsulinemia) most commonly reflects insulin resistance — the pancreas produces more insulin to keep glucose controlled. This can appear before fasting glucose or HbA1c become abnormal.

It is commonly seen with abdominal obesity, metabolic syndrome, fatty liver, early type 2 diabetes, and PCOS. Less common causes include insulinoma, insulin-releasing medications, exogenous insulin, Cushing syndrome, acromegaly, reduced insulin clearance, and assay interference.