Why Morning Blood Sugar Rises After 40 & How to Fix It

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Written by Jose Tejero, Exercise Physiologist

Waking up to high blood sugar can feel confusing and frustrating, especially when you’re trying to do everything right. You may skip breakfast, avoid late-night eating, or follow all your doctor’s instructions, and still see elevated morning glucose. If this sounds familiar, you’re not alone. Many people over 40 experience rising fasting blood sugar even when their diet hasn’t changed. The good news is that this pattern is reversible once you understand what’s happening inside your body.

Before we go deeper, it’s important to clear up one common myth: your morning blood sugar is not simply a reflection of what you ate the night before. Instead, it’s largely controlled by your liver and your hormones. Between 3-8 a.m., your body increases hormones like cortisol, growth hormone, and adrenaline to help you wake up and generate energy. This natural rise in hormones signals your liver to release glucose into your bloodstream-a process called the dawn phenomenon. In people who are insulin sensitive, this small glucose release is no problem. But when insulin resistance is present, the liver releases far more glucose than needed, causing those stubborn high morning numbers.

After age 40, several biological shifts make this even more likely. Here are the five biggest reasons fasting blood sugar gets worse with age-and the science-backed steps to turn it around.

1. Loss of Muscle Mass (Sarcopenia)

Beginning around age 40, adults naturally lose about 3-8% of their muscle mass per decade unless they actively work to maintain it[1]. Muscle is the body’s main storage site for glucose, so less lean mass means fewer “parking spots” for sugar. When muscle declines, glucose stays in the bloodstream longer-especially in the early morning hours.

Building and protecting muscle is one of the most powerful ways to improve insulin sensitivity and lower fasting blood sugar. Research shows that resistance training increases glucose uptake into muscles and improves insulin signaling[2]. A simple routine using bands, dumbbells, or even bodyweight movements like squats and pushups can be enough to make a noticeable difference.

Pairing strength training with a daily protein powder and 5 g of creatine has been shown to support stronger, denser muscle fibers and better metabolic function[3]. This combination is especially effective for adults over 40 who want to protect muscle as hormones shift with age.

 

2. Hormones Become Less Responsive With Age

As the years pass, hormones that once kept blood sugar steady-like insulin, GLP-1, and even melatonin-become less efficient. At the same time, cortisol tends to remain higher overnight, especially in adults who are under chronic stress or struggle with sleep. Elevated cortisol tells your liver to release more glucose, even if you haven’t eaten since the night before.

A helpful way to address this hormonal shift is through supplements that naturally reduce cortisol and support deeper sleep. Research shows that Ashwagandha can significantly reduce cortisol levels and improve stress resilience[4]. Magnesium glycinate, taken about one hour before bed, helps relax the nervous system and promote deep, restorative sleep[5]. When cortisol stays balanced through the night, the liver releases less glucose-meaning your morning blood sugar stays lower.

3. Declining Insulin Sensitivity

Insulin sensitivity tends to decrease gradually with each decade after 40. When cells don’t respond well to insulin, your liver continues releasing glucose because it mistakenly believes your body needs more energy. This is one major reason fasting glucose levels creep up over time.

One of the most well-studied natural options for improving insulin sensitivity is berberine. More than 50 clinical trials show that berberine lowers fasting glucose, improves A1c, and reduces insulin resistance[6]. Berberine works by activating AMPK, sometimes described as the “metabolic master switch,” thereby improving glucose uptake and helping regulate the liver’s glucose output.

Pairing berberine with a plant-forward, fiber-rich diet creates a powerful metabolic reset. Studies consistently show that diets high in fiber improve insulin sensitivity, reduce liver fat, and stabilize fasting glucose[7].

 

4. Increased Visceral Fat With Age

After 40, your body becomes more prone to storing fat around your organs-called visceral fat. This type of fat is metabolically active and releases inflammatory compounds that worsen insulin resistance and make the liver dump even more glucose overnight.

Fortunately, research shows that losing just 5-7% of body weight can significantly reduce visceral fat and improve fasting glucose[8]. Choosing lower-calorie-density meals, like vegetables, beans, whole fruits, and whole grains, helps naturally reduce visceral fat without extreme dieting. A plant-based, high-fiber meal plan can be especially beneficial. (You can download a free plan here).

 

5. Sleep Quality Declines With Age

Sleep naturally changes as we get older, and adults often experience less deep sleep. Even one poor night of sleep can raise fasting blood sugar by 20-25% the next morning[9]. Poor sleep increases cortisol and decreases insulin sensitivity, creating a perfect storm for high morning glucose.

Science shows several reliable ways to improve sleep:

• Keeping screens off 60 minutes before bed helps prevent melatonin suppression.
• A cool bedroom (around 65°F or 18°C) helps your core temperature drop, making it easier to fall asleep.
• A consistent sleep-wake schedule strengthens your circadian rhythm.
• Just 10 minutes of light stretching or deep breathing lowers nighttime heart rate and promotes deeper sleep.

Combining these habits with magnesium glycinate and Ashwagandha can be especially helpful.

 

6. Lower Daily Physical Activity

Many people naturally move less after 40 because of work demands, family responsibilities, or physical discomfort. But movement plays a major role in fasting glucose. Your muscles continue absorbing glucose for hours after you exercise-even without insulin.

Studies show that walking for just 10-15 minutes after meals significantly lowers post-meal and next-morning blood sugar[10]. If you’re choosing one time of day to move, make it right after your meals, especially your heaviest ones.

 

The Takeaway

If you’re waking up with high morning blood sugar, it’s not a sign of failure. It’s not caused by willpower, nor is it simply about what you ate the night before. It’s a combination of muscle mass, hormones, visceral fat, sleep patterns, and insulin sensitivity.

The encouraging news is that each of these areas is fixable. With the right habits-and support from targeted supplements like berberine, magnesium glycinate, protein, creatine, and Ashwagandha-you can restore insulin sensitivity, reduce liver glucose output, and start waking up with in-range numbers again.

For a free meal plan designed specifically to reverse insulin resistance, click here.

References

[1] Rosenberg IH. Sarcopenia: origins and clinical relevance. J Nutr. 1997.

[2] Holten et al. Strength training increases insulin-mediated glucose uptake in muscle. Diabetes (2004).

[3] Wax B, et al. Creatine for Exercise and Sports Performance, with Recovery Considerations for Healthy Populations. Nutrients (2021)

[4] Arumugam V, et al. Effects of Ashwagandha (Withania Somnifera) on stress and anxiety: A systematic review and meta-analysis. Explore (2024).

[5] Arab A, et al. The Role of Magnesium in Sleep Health: a Systematic Review of Available Literature. Biol Trace Elem Res.(2023).

[6] Yin et al. Berberine improves insulin resistance and glucose metabolism. Metabolism (2008).

[7] Weickert & Pfeiffer. Impact of Dietary Fiber Consumption on Insulin Resistance and the Prevention of Type 2 Diabetes. Nutrition Journal (2008).

[8] Magkos F. et al. Effects of Moderate and Subsequent Progressive Weight Loss on Metabolic Function and Adipose Tissue Biology in Humans with Obesity. Cell Metab. (2016)

[9] Donga E, et al. A single night of partial sleep deprivation induces insulin resistance in multiple metabolic pathways in healthy subjects. J Clin Endocrinol Metab. (2010)

[10] Reynolds et al. Advice to walk after meals is more effective for lowering postprandial glycaemia in type 2 diabetes mellitus than advice that does not specify timing: a randomised crossover study. Diabetologia (2016).