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Why is fasting insulin so important to check in the fight against diabetes?

Writer's picture: Gemma Westfold Gemma Westfold

Because high fasting insulin is a precursor to insulin resistance and type 2 diabetes.

Type 2 diabetes often develops silently over the course of several years before blood glucose or HbA1c tests reveal a problem. What many don’t realize is that insulin levels can start rising long before these common markers of blood sugar dysregulation become apparent. In fact, elevated fasting insulin can be one of the first signs that your pancreas is working overtime to maintain normal blood glucose levels, paving the way for insulin resistance and, eventually, type 2 diabetes.


What is insulin?

Insulin is a hormone produced by the pancreas that plays a crucial role in controlling blood sugar (glucose) levels. After you eat, carbohydrates are broken down into glucose, which enters the bloodstream. If you're a client or you have done one of my programs, think of the blood sugar graph I use. In response, the pancreas releases insulin, which helps cells absorb glucose for energy or store it for future use.

Over time, however, various factors—such as poor nutrition, inactivity, and excess weight—can cause cells to become less responsive to insulin. They stop listening to it. This phenomenon, known as insulin resistance, forces the pancreas to produce more insulin to keep blood sugar levels in check. While blood glucose levels may remain normal for a time, insulin levels can rise dramatically.


Fasting Insulin

Fasting insulin levels can be tested easily via a blood test and provide an early indication of how hard the pancreas is working to maintain normal glucose levels. Elevated fasting insulin (hyperinsulinemia) can occur even when fasting glucose levels are normal. Research has shown that measuring fasting insulin can help identify individuals at high risk for developing insulin resistance and type 2 diabetes before other markers, like glucose or HbA1c, reveal abnormalities. This finding highlights the importance of measuring insulin levels early, as fasting glucose alone may not provide a complete picture of metabolic health.


The Silent Rise of Insulin Before Blood Sugar Changes

One of the main issues with relying solely on glucose or HbA1c tests is that they only provide a snapshot of blood sugar levels and don’t reflect the underlying hormonal imbalances. According to a study published in The Journal of Clinical Endocrinology and Metabolism, insulin levels can rise significantly even when glucose levels remain stable. During this time, the pancreas compensates by producing more insulin to manage glucose levels. However, as insulin resistance worsens, the pancreas eventually becomes unable to keep up with the demand, leading to increased blood glucose and, ultimately, the diagnosis of diabetes.



What symptoms to look out for that may indicate Insulin Resistance or elevated insulin

Despite being a precursor to diabetes, insulin resistance and hyperinsulinemia often go unnoticed, as they don’t always present with obvious symptoms. However, some signs may point to an underlying problem, including:

  • Weight gain, especially around the abdomen: Insulin promotes fat storage, particularly in the abdominal region. This type of fat accumulation is linked to an increased risk of metabolic syndrome and type 2 diabetes. In menopause, women naturally become more insulin resistant due to the loss of insulin sensitising oestrogen. This is the main driver of the menopausal abdominal weight gain.

  • Fatigue: Insulin resistance can interfere with the body’s ability to efficiently use glucose for energy, leading to feelings of tiredness. I see this often in clinic.

  • Cravings for carbohydrates: Elevated insulin levels can cause blood sugar swings, leading to cravings for sugary and starchy foods.

  • Increased hunger: Insulin resistance can impair satiety signals, leading to excessive hunger despite adequate food intake.

  • High blood pressure: Elevated insulin levels can increase sodium retention, contributing to hypertension.

  • Skin changes: A condition called acanthosis nigricans, characterized by dark, velvety patches of skin, often occurs in individuals with high insulin levels and insulin resistance as well as an increase of skin tags.




Blood tests that can detect early insulin resistance and put you in charge

Relying solely on glucose or HbA1c tests to monitor for insulin resistance can be misleading, as these markers may remain normal in the early stages of the condition. To get a more accurate picture of metabolic health, the following tests can be useful:


  1. Fasting Insulin: Elevated fasting insulin levels are one of the earliest indicators of insulin resistance. Ideally, fasting insulin should be less than 6 μU/mL, although optimal levels may vary slightly depending on the laboratory. This test isn’t run as standard on the NHS but I run it for my clients with a private lab as part of my Wellness Check as well as my 12-week programs.

  2. Fasting Glucose and HbA1c: While these tests may remain normal for years, they should still be monitored, especially if insulin levels are elevated. A fasting glucose level below 5.5mmol/L and an HbA1c below 41 are considered normal by NHS standards but functional medicine would look at an Hba1c reading of 37mmol/mol or below for optimal health and to turn the tide on insulin resistance. At this point you really want to know what insulin is doing to keep blood sugar in range.

  3. Triglyceride-to-HDL Ratio: High triglycerides and low HDL (high-density lipoprotein) cholesterol are often associated with insulin resistance. A triglyceride-to-HDL ratio greater than 3 can indicate insulin resistance.


If you have access to your NHS blood test results, then see if you are on the higher end of normal and if you need to really pay attention to the advice below, or book a free call with me.


What can you do about it and how to manage elevated insulin

The good news is that insulin resistance and hyperinsulinemia are reversible, especially when detected early. Lifestyle changes can significantly improve insulin sensitivity and reduce the risk of progressing to type 2 diabetes.


  1. Nutrition: Adopting a low-carbohydrate, low processed food, high-fibre, omega 3 rich diet (think of a Mediterranean diet) can help regulate blood sugar levels and reduce insulin demand. A study published in The American Journal of Clinical Nutrition found that a low-carbohydrate diet significantly lowered fasting insulin levels in overweight individuals with insulin resistance.

  2. Exercise: Regular physical activity, particularly strength training and cardio, improves insulin sensitivity by increasing glucose uptake in muscle cells independent of insulin. According to research in Diabetes & Metabolism, even moderate exercise can reduce insulin levels and improve glucose metabolism.

  3. Weight loss: Shedding excess weight, especially around the abdomen, can reduce insulin levels and improve insulin sensitivity. A weight loss of just 5-10% can have a significant impact on metabolic health.

  4. Sleep and stress management: Poor sleep and chronic stress can increase insulin resistance. Prioritising restful sleep and practicing stress-reduction techniques, such as mindfulness or yoga, can support metabolic health.


Final thoughts

Elevated insulin levels are one of the earliest signs of insulin resistance, often long before changes in blood glucose or HbA1c levels become apparent. Measuring fasting insulin and other metabolic markers can provide crucial insight into a person’s risk for developing type 2 diabetes.


I recommend this as standard with all clients, especially those with unjustified fatigue, menopausal symptoms and those looking to lose weight.  By making lifestyle changes such as improving nutrition, increasing physical activity, and managing weight, you can reverse insulin resistance, lower fasting insulin levels, and reduce your risk of developing diabetes.


This is where I can step in, offer testing so that you can see exactly where you are with your blood sugar management and put together a personalised nutrition and lifestyle plan that is achievable and fits in with your life, yet powerful enough to create change. Book your free 20-minute mini consultation here.




How I can help with Nutritional Therapy

Using the functional medicine approach, I work to understand your metabolic health and what is impacting your healthspan. You can expect from me:


  • A personalised nutrition plan rich in nourishing foods to assist your glucose management and metabolic health

  • Test recommendations and full interpretation either privately or through your GP

  • Personalised supplement protocol to support your blood sugar management and reliance on insulin

  • Regular consultations and coaching to support new choices


Note: as a Nutritional Therapist, I do not diagnose or prescribe, however I do use functional nutrition testing to help find the best way to support my client’s health. Book your free call here

 

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