Key Takeaways:

  1. Fasting insulin is a crucial measure of metabolic health, providing insights into the risk of developing insulin resistance or type 2 diabetes.
  2. High fasting insulin levels, known as hyperinsulinemia, can indicate insulin resistance and are linked to several health conditions, including heart disease and cancer.
  3. A meta-analysis found a potential association between higher fasting insulin levels and increased all-cause mortality risk.
  4. Reference ranges for fasting insulin levels vary, but lower levels are often associated with better insulin sensitivity and reduced health risks.

The importance of insulin in American health care is multifaceted. It is not only a cornerstone in the treatment and management of diabetes but also a focal point in public health discussions, economic considerations, and medical research. Insulin’s role transcends individual health, affecting societal and economic aspects, and remains a key area of focus in efforts to improve health outcomes and quality of life for those with diabetes. Its significance in the American health context is highlighted by the prevalence of diabetes and its associated health risks. Without proper insulin management, individuals with diabetes face a heightened risk of severe health complications, including heart disease, stroke, kidney failure, vision loss, and nerve damage. Thus, insulin therapy is not just a means of managing diabetes but also a critical tool in preventing these life-threatening conditions.

What is fasting insulin?

Insulin is a hormone produced by the pancreas that helps regulate blood sugar (aka glucose) levels. Glucose, the building blocks of carbohydrates, is a major source of energy for our cells. After eating, our bodies secrete insulin in response to circulating glucose to prompt our cells to either store it for future use or immediately convert it to energy. Essentially, insulin helps to regulate blood sugar levels by reducing the concentration of glucose in the bloodstream.

As the name suggests, fasting insulin is a measurement of insulin levels in the bloodstream after a period without glucose-containing food or beverages, typically for 8-12 hours to bring insulin and glucose levels back to baseline. 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 of 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 1.90 and 23.00 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.

How to Lower Fasting Insulin Levels

Given what we know about the systematic secretion of insulin in response to glucose, a high level of insulin in the blood is associated with high circulating blood glucose levels. But what can we do to naturally alleviate this? In other words, how can a person regain insulin sensitivity and lower blood glucose levels?

  • A high BMI can worsen the body’s sensitivity to insulin so consider healthy ways of losing weight. [2]
  • Incorporate exercise into your daily routine. While there is no consensus on whether a greater intensity of exercise yields higher insulin sensitivity and lower HbA1c (learn more about HbA1c here), some studies do support that HIIT (high-intensity interval training) may be as salubrious as moderate-intensity exercise. [3] Either way, get up and get moving!
  • Stay active while you’re seated by doing “soleus push-ups” (calf raises). [4]
  • Eat fiber-rich foods before carbs to slow glucose absorption and dampen glucose spikes. [5]
  • Get 7-8 hours of quality sleep every night. [6]
  • Consider intermittent fasting, which has been shown to potentially improve insulin sensitivity, blood pressure, oxidative stress, and appetite. [7]
  • A CGM (continuous glucose monitor) used over several weeks may help you pinpoint which foods spike your glucose and, therefore, insulin. [8]

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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.