Elevated serum insulin is a compensatory response to insulin. Why does this happen? We can explain this with a simple analogy, for example, 1 IU of insulin normally lowers blood glucose by 2 mmol/l. When insulin efficacy decreases or the sensitivity of peripheral tissues to insulin decreases, insulin needs to secrete 4 IU or more to lower blood glucose by 2 mmol/l, which leads to an increase in insulin levels, which we also call insulin resistance. Why does insulin resistance occur? The most common clinical reason is obesity. Because obese patients with high body fat content, high fat content will lead to a decrease in insulin sensitivity to the role of fat, resulting in increased insulin compensatory secretion.