I Wore a Glucose Monitor for a Month—Here’s What Surprised Me

As a nutritionist, I’ve spent years helping people balance blood glucose (or blood sugar) through diet and lifestyle. However, I’ve often struggled with maintaining a healthy fasting morning glucose despite having a low-sugar diet and engaging in regular exercise. It was time to take a deeper look and see my glucose levels in real time.

My Sanoviv doctor and I wondered whether we would gain additional insight if I wore a continuous glucose monitor (CGM) for 30-45 days. My motivation was partially medical, since according to my lab values, I was borderline “pre-diabetes.” But I also wanted to know more about how CGMs work and how they can help when customizing a person’s diet. I was curious to know:

• How do my meal choices really affect me?
• Does stress, sleep, or monitoring workouts affect my glucose?
• Are the foods that are considered “healthy” and low-sugar always supportive of metabolic balance?

Continuous glucose monitors (CGMs) are small sensors worn on the back of the arm that measure glucose levels in real time throughout the day. The data can be incredibly revealing. What I discovered after six weeks changed how I think about food, movement, and biochemical individuality.

What I Learned from Seeing My Glucose in Real Time

I spent my first week with the CGM eating my normal diet with the goal of observing and making detailed notes. The biosensor pairs with a smartphone and shows your glucose patterns. Not only did I record data from the CGM, but I also performed finger-prick glucose measurements to compare and evaluate the sensor’s accuracy. Here are a few important considerations:

• The CGMs measure glucose in the interstitial fluid (the liquid between cells).
• The readings are more accurate after the first 24 hours.
• Too much pressure on the biosensor can affect the readings.
• When comparing fingerstick glucose with interstitial fluid glucose, rapidly changing glucose can be difficult to match because your blood glucose changes before interstitial fluid does. The readings are closer when glucose stabilizes. There is about a 15-20-minute delay in the CGM reading after eating or exercising.

That first week was somewhat stressful as I noticed some significant glucose spikes. The phone app records significant spikes or glucose drops — anything outside of the 70-140 mg/dl range. Keeping glucose within that range shows good blood sugar balance and control. After eating, glucose should rise and fall gradually within that range.

As you can see, after I made some adjustments, I was able to maintain my glucose withing the recommended range. Just by making some small changes, my energy and sleep improved. I also noticed less hunger, fewer cravings, and felt confident about improving my metabolic health, knowing how important that is to longevity and quality of life. So, what caused these spikes and what adjustments to my eating did I make? Here are a few examples that provided a learning experience:

• Just about any fruit, low sugar or otherwise caused spikes. The lower sugar fruits (blueberries, raspberries) caused a much smaller spike than watermelon, which was expected. However, eating three pieces of watermelon by itself caused a large spike. I adjusted my meals so that I ate only low sugar fruits and at the end of a meal. I also decreased the quantity of the fruit serving.
• Nearly every starchy carbohydrate (homemade sourdough bread, rice, potatoes, tortilla chips) caused a spike, even if I ate it at the end of a meal and with sufficient protein and fat (that surprised me). The only food in this category that did not cause a spike was a cold, purple sweet potato salad. This is most likely due to its resistant starch content.
• The largest spike I saw during my experimentation phase (after the watermelon), was from French onion soup I had at a restaurant (my glucose went up to 190). I thought because of the cheese (fat), the glucose response would have been less. But then I thought about the onions. Were they caramelized? And, what about the small piece of bread? After seeing this, I realized I should have had a salad first and asked for the soup to be served without the bread. Although I knew this, it was refreshing to have it confirmed.

This first week of observation helped me learn more about how specific foods affected me. I am very sensitive to starchy carbohydrates and need to consider how to incorporate these into my diet without a glucose spike. This taught me what research already confirms: there’s enormous inter-individual variability in post-meal glucose response, even to identical foods.¹

How to Avoid Glucose Spikes Without Restrictive Eating

1. Consider meal composition and order. On days when I ate protein and vegetables before carbs, my glucose curve was flatter and more stable. The same meal, eaten in reverse order, caused a noticeable spike. This pattern aligns with research showing that “meal sequencing”—eating vegetables and protein before carbohydrates—can reduce the rises in post-meal glucose.² It works by slowing gastric emptying and moderating the rate of carbohydrate absorption. This sequencing can reduce post-meal glucose by 30–40%.
2. Try apple cider vinegar about 10 minutes before meals. Mixing 1 tablespoon of apple cider vinegar (ACV) in water before a meal containing starchy carbohydrates may help lower post-meal glucose levels.^3,4 The acetic acid found in vinegar appears to slow gastric emptying and enhance muscle glucose uptake—leading to smaller glucose spikes. I did experiment with this using the exact same meals, and it helped slightly.
3. Movement after meals makes a big difference. Even a short walk after meals—10 minutes around the block—had a significant effect. My post-meal spikes decreased by up to 25%. Studies confirm that light activity after eating enhances glucose uptake by muscle tissue and improves insulin sensitivity.⁵
4. Pair carbohydrates with protein and fat. Instead of eating carbohydrates alone (like I did with that watermelon snack), combine them with foods that slow digestion—nuts, cheese, yogurt, or lean protein. This did make a difference, but I still opted for smaller carbohydrate portions and lower-sugar fruits.
5. Quantity matters much more than I expected. I did a “pizza experiment.” During the first one, I ate four slices of a thin-crust cheese pizza with roasted mushrooms, leaving the crust behind. The following week I ate a spinach salad first with cherry tomatoes, cucumbers and Italian dressing, then two slices of the same pizza and the glucose response was much better! In fact, whenever I had a large amount of food, my glucose spiked and took longer to stabilize. This made me think about what could be happening with too much food, even if the meal composition is healthy.

Other Factors to Consider for Better Glucose Balance

• I saw noticeable glucose spikes after periods of poor sleep or high stress, even when I ate the same foods. When you experience stress, elevated cortisol levels increase glucose and impair insulin’s effectiveness. Remember, quality sleep and ongoing stress management are key components in metabolic health.
• I also wondered why my fasting glucose in the morning is always around 98-102. Through monitoring, I learned that my glucose drops between 2 and 4 a.m., signaling my body to convert stored carbohydrates into glucose. This is known as the dawn effect or dawn phenomenon, a natural increase in glucose levels that occurs early in the morning, usually between 2 and 8 a.m. The dawn effect occurs due to hormonal changes that stimulate the liver to produce and release glucose. This, too, improved over time as I worked on a better overall blood sugar balance.
• Weight loss improves glucose balance. During my CGM experiment, I lost seven pounds just by focusing on glucose control. Being even slightly overweight, especially with excess fat in the abdominal area, significantly contributes to insulin resistance,⁶ which occurs when the body’s cells don’t respond effectively to insulin (leading to higher blood sugar). Even when weight loss is slow and gradual, you can expect it to improve blood sugar balance.

What CGMs Reveal About Your Metabolism

A CGM doesn’t just show numbers—it shows your body’s metabolic fingerprint. Unlike a single lab test, it reflects how food, stress, sleep, and hormones interact day by day. Wearing a CGM can show:

• Early clues about insulin resistance. Subtle elevations or prolonged post-meal glucose may signal early dysregulation—even when standard blood labs look normal.
• Real-time feedback for sustainable change. Seeing how your lifestyle choices affect your glucose levels provides personalized information and motivation that generic advice can’t match. This is where you can actually see the benefit of lifestyle changes, such as a post-meal walk or a protein-first breakfast, on your own body.
• Personalized nutrition at its best. What’s healthy on paper or according to research may not be optimal for you. For example, my husband can drink a glass of fresh-squeezed orange juice with minimal glucose impact, while that would undoubtedly cause a spike in my glucose. A CGM can empower you to customize your diet to your own physiology rather than to trends or averages.

How to Know if You’re Insulin Resistant

For looking at blood sugar balance, these are the laboratory tests that are essential in providing a complete picture of metabolic health:

1. Fasting glucose – common in most blood panels
2. Fasting insulin – uncommon (you may have to ask for this)
3. Hemoglobin A1C (glycated hemoglobin) – an indicator of blood sugar control over a three-month period
4. HOMA-IR – a strong indicator of insulin resistance (the equation uses fasting glucose and fasting insulin)
5. Triglyceride to HDL ratio – a strong predictor of insulin resistance

Here is a chart showing the optimal ranges for these markers:

Biomarker	Functional Medicine Optimal Range	Conventional  Reference Range	What It Indicates
Fasting Glucose	75–85 mg/dL	70–99 mg/dL	Reflects baseline glycemia. Levels >90 mg/dL may suggest early insulin resistance or stress-related glucose elevation.
Fasting Insulin	2–5 µIU/mL (optimal ~3)	2–25 µIU/mL	Elevated insulin with normal glucose indicates compensated insulin resistance. Many practitioners flag >8 µIU/mL as early metabolic dysfunction.
Hemoglobin A1C (HbA1c)	4.8–5.2 %	≤5.6 % (prediabetes ≥ 5.7 %)	Reflects 3-month glucose exposure. Levels >5.3 % may correlate with increased glycation and oxidative stress risk.
HOMA-IR (Homeostatic Model Assessment of Insulin Resistance)	< 1.0 (optimal)	< 2.0 (generally “normal”)	Calculated as (Glucose × Insulin) / 405.  < 1.0 suggests excellent insulin sensitivity; 1.5–2.0 = early insulin resistance 2.0-3.0 = moderate insulin resistance >3.0 = severe insulin resistance
Triglyceride-to-HDL Ratio (TG:HDL)	< 1.0 (optimal)	< 3.5 (often cited “normal”)	Strong predictor of insulin resistance, hepatic fat, and cardiovascular risk. 1.0-1.5 = mild insulin resistance >1.5 = strong indicator insulin resistance Ratios > 3.0 are linked to increased cardiometabolic risk.

CGM Units That I Tried

I used two different, popular brands. The typical cost is about $90 for four weeks. I started with the Stelo CGM from Dexcom. This is their CGM for non-diabetics. I noticed this sensor consistently measured slightly higher than finger-prick glucose meters. Since that caused me some anxiety with seeing readings 15-25 mg/dl over what my glucose meter was showing, I decided to try another brand, just to compare.

The next brand I tried was Lingo CGM, from Abbott, their CGM for non-diabetics. The Lingo was insightful because it also gives you a “lingo target” as you improve glucose balance. This sensor seemed much closer to my standard blood glucose meter, but it often underestimated glucose, providing readings that were lower than the fingerstick method.

Both brands offer insight into glucose patterns and show spikes (when your glucose rises above 140 mg/dL). Continuous Glucose Monitoring can be a powerful self-awareness tool, but it isn’t right for everyone. For some individuals, CGMs can increase anxiety, obsessive behaviors, or misinterpretation of data rather than promote balanced health. Although I’m a knowledgeable nutritionist, the Stelo brand (with higher readings) did cause me some anxiety during the learning process.

Who Should Not Use a CGM?

Although CGMs provide excellent information and can help people learn about how foods and lifestyle affect their individual blood glucose, some people should not use a CGM:

• People with a current or past eating disorder – CGM use can reinforce obsessive tracking, rigid control of food intake, or guilt around glucose spikes. Studies show that biofeedback tools can exacerbate disordered eating patterns.⁷ Such individuals may benefit more from interoceptive awareness (body cues, hunger, satiety) than from external feedback and should avoid CGMs unless prescribed and monitored by a health professional.

• People with anxiety, obsessive-compulsive disorders, or perfectionistic tendencies – Real-time data can lead to hypervigilance or health anxiety, especially when normal variations are misinterpreted as “bad.” This can worsen cortisol levels and sleep quality, which can harm metabolic health. A food and symptoms journal may be a good alternative to offer insight without triggering anxiety loops.

• Those without a clear purpose or guidance – Without context, some people may misinterpret normal physiological glucose fluctuations and make unnecessary dietary restrictions. For example, avoiding all fruit or carbohydrate because of transient spikes misses the big picture of nutrient quality, food quantity, fiber, and insulin sensitivity.

• People with certain skin conditions or sensitivities – CGM sensors can cause contact dermatitis, irritation, or allergic reactions to adhesives, especially in those with eczema or psoriasis.⁸

• Those with severe bleeding disorders or currently on anticoagulant therapy – The CGM filament is inserted under the skin and can pose a bleeding or bruising risk in these individuals.

• People using implanted electronic devices – Some CGM transmitters may interfere with other electronic medical devices. Always check device compatibility and use only under a physician’s care.

Those who might benefit most when used properly include people with prediabetes, insulin resistance, PCOS, or metabolic syndrome. Also, CGMs may help those who want to optimize nutrition for athletic performance, longevity, or energy stability. In all cases, education and emotional readiness are essential. A CGM monitor should empower, rather than shame, the user.

My Biggest Takeaway

Wearing a CGM was like turning on a light switch for my metabolism. I no longer think of glucose management as just a concern for diabetics—it’s a vital part of energy, mood, and long-term health. It’s also key to preventing many chronic diseases.

The experience reminded me that food is information, and our bodies are constantly listening. For anyone curious about how their body responds to daily habits, a short-term CGM experiment can be eye-opening. You don’t need to wear one forever—just long enough to learn your body’s language. When you understand your own glucose patterns, you can make choices that truly work for you, not against you.

Remember, we are all biochemically unique, and CGMs are one way to help create an individualized nutrition plan.

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References

1. Zeevi D, Korem T, Zmora N, et al. Personalized nutrition by prediction of glycemic responses. Cell. 2015;163(5):1079-1094.
2. Shukla AP, Iliescu RG, Thomas CE, Aronne LJ. Food order has a significant impact on postprandial glucose and insulin levels. Diabetes Care. 2015;38(7):e98–e99.
3. Johnston CS, Kim CM, Buller AJ. Vinegar improves insulin sensitivity to a high-carbohydrate meal in healthy adults. Eur J Clin Nutr. 2004;58(9):1139–1144.
4. Östman E, Granfeldt Y, Persson L, Björck I. Vinegar supplementation lowers glucose and insulin responses and increases satiety after a bread meal in healthy subjects. Eur J Clin Nutr. 2005;59(9):983–988.
5. Reynolds AN, Mann J, Williams S, Venn BJ. 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 randomized crossover study. Diabetologia. 2016;59(12):2572–2578.
6. Handy RM, Holloway GP. Insights into the development of insulin resistance: Unraveling the interaction of physical inactivity, lipid metabolism and mitochondrial biology. Front Physiol. 2023;14:1151389. 
7. Levinson CA, Fewell L, Brosof LC. Eating disorders and obsessive–compulsive disorder: The role of shared temperament and executive functioning. Curr Psychiatry Rep. 2017;19(8):54.
8. Heinemann L, Freckmann G. CGM adhesives and skin reactions: A critical issue. J Diabetes Sci Technol.2015;9(6):1282–1288.