CHAPTER 1: Why Measure Your Fasting Insulin Levels and What the Results Mean

What is fasting insulin

Fasting insulin is a measurement of insulin levels in the bloodstream after a period of fasting, typically 8-12 hours. Insulin is a hormone produced by the pancreas that helps regulate blood sugar levels by allowing glucose to enter cells to be used for energy or stored for future use. Assessing fasting insulin levels can provide valuable insight into an individual’s metabolic health and their risk of developing insulin resistance or type 2 diabetes.

Why measure fasting insulin levels? A link to longevity

Measuring fasting insulin levels can help identify early signs of insulin resistance, a condition where the body’s cells become less sensitive to insulin, leading to the pancreas producing more insulin to maintain normal blood sugar levels. Early detection of insulin resistance can help prevent the progression to prediabetes or type 2 diabetes. Moreover, monitoring insulin levels can provide a more comprehensive understanding of one’s metabolic health and inform necessary lifestyle and dietary changes to improve it.

Chronically high fasting insulin levels, known as hyperinsulinemia, can be an indicator of insulin resistance and other health issues. High insulin levels have been linked to several health conditions, including metabolic syndrome, heart disease, cancer, cognitive decline, reproductive health issues, and fatty liver disease.

A meta-analysis of three studies (n=14,723) identified a close-to-significant association (p=0.058) between relatively higher fasting insulin levels and an increased all-cause mortality risk. This analysis included participants from Sweden and the US, ranging in age from 20 to older than 65 years old. The pooled relative risk (RR) of all-cause mortality was 1.13 (95% CI: 1.00-1.27) for the highest compared to the lowest category of fasting insulin levels. There was no significant evidence of heterogeneity across the studies [1].

Interpretation of insulin test results and optimal ranges

Insulin levels can vary depending on several factors, including whether or not you have fasted before the test. Fasting insulin tests require you to avoid eating or drinking anything except water for 8-12 hours before the test. If you have not fasted, your insulin levels could be higher due to the body’s response to food intake, which might not provide an accurate representation of your baseline insulin levels.

General reference ranges for fasting insulin levels vary by laboratory, but a common range is between 2.6 and 24.9 µIU/mL (micro international units per milliliter). It is essential to note that these reference ranges may not necessarily represent optimal insulin levels for overall health.

While there is no scientific consensus on the optimal insulin levels, some experts suggest that a fasting insulin level below 10 µU/mL is ideal for maintaining good metabolic health. Lower insulin levels are often associated with better insulin sensitivity and a reduced risk of insulin resistance, which can lead to various health issues such as Type 2 diabetes, heart disease, and other chronic conditions.


Disclaimer: If you have any medical questions or concerns, please talk to your healthcare provider. The articles on the SiPhox Health Hub are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis or treatment.