Insulin (Fasting)
Also called: Insulin, Fasting insulin
Insulin is the hormone driving glucose uptake into cells. A high fasting insulin reflects insulin resistance — the upstream lesion of type 2 diabetes — often years before glucose rises.
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What does Insulin (Fasting) measure?
Insulin is secreted by pancreatic beta cells in response to rising blood glucose. It tells liver, muscle and fat cells to absorb glucose. In insulin resistance, those tissues respond poorly, so the pancreas compensates by secreting more insulin to achieve the same effect — hyperinsulinaemia. Because the body buffers glucose for years using this compensatory mechanism, fasting glucose and HbA1c can stay normal long after insulin levels have climbed. Fasting insulin is therefore the earliest practical lab marker of metabolic dysfunction. The HOMA-IR score (fasting insulin × fasting glucose / 405) quantifies resistance.
What does a high Insulin (Fasting) level mean?
- Insulin resistance — by far the most common cause; precedes type 2 diabetes by 5–10 years.
- Metabolic syndrome — central component.
- Obesity, sedentary lifestyle, high-refined-carb diet — the modifiable drivers.
- Polycystic ovary syndrome — insulin resistance is a defining feature.
- Cushing's syndrome, acromegaly — endocrine causes (rare).
- Insulinoma — very rare tumour producing insulin; presents with hypoglycaemia.
What does a low Insulin (Fasting) level mean?
- Type 1 diabetes — autoimmune destruction of beta cells.
- Late-stage type 2 diabetes — beta-cell exhaustion after years of overproduction.
- Recent acute illness or steroid use — variable.
- Strict caloric restriction or fasting — physiological.
When to discuss with a doctor
Fasting insulin >10 µU/mL or HOMA-IR >2 suggests early insulin resistance and is a high-leverage intervention point: lifestyle change (low-refined-carb diet, weight loss, regular aerobic exercise, resistance training) is more effective at this stage than after glucose has risen. Pair with fasting glucose and HbA1c. Mediora.AI plots fasting insulin trajectory alongside the rest of the metabolic panel.