Desde entusiastas del fitness a personas influyentes en el bienestar, e incluso la gente común que me encuentro en mi gimnasio local, muchas personas están utilizando monitores de glucosa capilar (MCG) como una herramienta para "optimizar" el metabolismo. Esto ha despertado mi curiosidad como persona concienciada con la salud, pero lo más importante es que, como médico, los pacientes me han hecho esta pregunta, deseosos de saber cuál es la postura de la comunidad médica al respecto. Así que he hecho el trabajo preliminar en este artículo para asegurarme de que sé, y sabemos, cómo responder de una manera basada en la evidencia y realista, pero que también apoye a los pacientes a tomar las riendas de su propia salud.

The Rise to Popularity
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CGMs were made to help people with diabetes monitor their blood sugar levels. It’s a small, discrete device that sits just under the skin (usually on ones arm) and tracks blood sugar levels in the interstitial fluid continuously, rather than needing frequent finger prick tests.  Since they gained FDA approval in 2024, they are now widely available over-the-counter for anyone to buy - whether they have a diagnosis of diabetes or not.They are marketed for their ability to detect glucose levels or ‘glucose spikes’, identify early signs of pre-diabetes or diabetes (glucose dysregulation), and help empower individuals to make informed changes by linking glycaemic fluctuations to specific dietary and lifestyle behaviours. [1,2] As each individual has a different glucose response to the same foods, CGMs could provide highly tailored nutritional advice by addressing those variations. [3] For instance, foods that have been linked with a lower postprandial glucose responses (PPGRs) are identified, and people may want to prioritise them over those that elicit higher responses.  [4]But whether CGMs can really produce these claimed health outcomes in individuals without diabetes is very uncertain.

Hype or Hope?
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So the verdicts out: are they truly beneficial, or an example of healthtech hype outpacing evidence? Here are some things healthcare professionals need to know:

Glucose Fluctuations Are Normal
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One of the biggest misconceptions driving CGM use among healthy individuals is this idea that ‘glucose spikes’ are harmful. Glucose levels naturally fluctuates throughout the day – after meals, during exercise, in response to stress. This is just how the body works.The concern isn’t the rise and fall of glucose itself, but rather when glucose levels remain consistently high, as this can be a sign of underlying insulin resistance. [5] It is however important to note that insulin resistance, which can be a precursor to pre-diabetes and diabetes, is primarily driven by weight gain and sedentary lifestyles – not the occasional postprandial glucose rise.Furthermore, many other factors affect post prandial glucose levels, including age, BMI, menopause status and gut microbiome. Studies have shown that genetics and the meal time of day explained the most inter-individual variation in CGM postprandial glucose responses - rather than meal composition. [6]We need to reassure our non-diabetic patients coming to us concerned about ‘glucose spikes’ that variability is a normal physiological response. The focus should be on overall health – not an isolated glucose reading.
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The Accuracy and Limitations of CGMs
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It is important to acknowledge the technological limitations of CGMs. These devices measure glucose in the interstitial fluid rather than directly in the bloodstream, and relies on algorithms to estimate actual glucose levels. In non-diabetic individuals, this can sometimes yield less reliable data, particularly if the devices are not designed or calibrated for non-diabetes ranges. It also introduces a margin of error, with studies showing CGMs can overestimate peaks by up to 20%. In healthy individuals, who have a much smaller range  of blood glucose, this discrepancy can be significant, and can lead to misinterpretation and “misdiagnosis”. [7] Patients don’t often don’t realise this about CGMs, which can cause a lot of unnecessary anxiety over completely normal fluctuations.

CGMs are therefore not suitable for diagnosing diabetes. Current clinical guidelines do not recommend CGMs outside of people living with type 1 diabetes (T1DM) or insulin-treated T2DM. [8]What they can be useful for though, is to help identify trends over time, as opposed to having a knee-jerk reaction to an individual number.

There is limited evidence in non-diabetic individuals
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CGMs are incredibly valuable in the management of conditions such as type 1 diabetes, insulin-dependent type 2 diabetes, and gestational diabetes. At present, there is no convincing evidence that CGMs lead to better metabolic outcomes in those without diabetes, with limited evidence of extensive longitudinal studies showing that wearing a CGM leads to better long-term metabolic health. Without this, CGM data interpretation remains largely speculative.There is an argument for CGMs enhancing engagement with lifestyle changes, as individuals can associate and visualise lifestyle factors corresponding with high or low glucose results, and make adjustments based on this.  [9] However, this boils down to a couple of things:

- Adoption - many people may not understand the meaning of the CGM data and thus may not fully engage.
- Accuracy of the device - overestimation of blood sugar levels can lead to misinterpretation.
- User education - if knowledge of glucose ‘spikes’ causes the exclusion of healthy, carbohydrate containing food (e.g. whole grains), this may result in an overall less healthy diet. A very important point to note as well, is that for some individuals, CGM use could do more harm than good - encouraging excessive food restriction, unhealthy avoidance of carbohydrates, and even contributing to disordered eating behaviours.

Where CGMs Can Help – And Where They Can’t
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Without a doubt, these devices are useful. But knowing the context in which this data should and can be used, as well as the risks it brings, is essential to any clinician.

Instances where CGMs are useful:
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Monitoring disease conditions:
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‍CGMs have clinically well-established uses in monitoring conditions such as Type 1 diabetes and insulin-treated type 2 diabetes, gestational diabetes and post-operative and critical care settings. [10]  There is also emerging evidence in the management of migraines and reactive hypoglycaemia. [11]

Instances where CGMs may be useful:
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Early Diagnosis
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A standardised method and diagnostic criteria are essential before CGMs can be accepted as a tool for diagnosing diabetes, however, CGM data can provide early signals that may prompt the need for traditional diagnostic tests for diabetes. This isn't yet sufficient on its own for a formal diagnosis, but can be a useful prompt. Given that youth-onset type 2 diabetes can lead to an earlier onset of  of both macro-vascular and microvascular complications, early detection and intervention is even more so important for preventing life-limiting complications later in life. [12]While more research is needed in this area, it’s certainly something to keep an eye on, as the sooner type 2 diabetes is recognised in young individuals, the better the chances are for effective management and reducing the risk of long-term complications.

Athletes and Elite Sports
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There is some very premature evidence on the utility of CGMs in enhancing performance in this group of athletes. For instance, an interesting study on ultramarathon runners found that running speeds correlated significantly with glucose concentrations and with energy/carbohydrate intake.[13]  Some clinicians have also suggested that there is an ‘ideal’ glucose range that is lower than what’s typically considered unhealthy - where the body functions at peak performance. They believe that maintaining blood sugar within this narrow range could enhance overall health, reduce occasional spikes (which was viewed as harmful), and potentially lower the risk of developing type 2 diabetes. At present, there is no evidence for this. However, there has been little research in this area because CGM data is so new, and almost all the CGM data in the literature are in people with diabetes.

Obesity
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Given obesity is the greatest risk factor for the development of diabetes, it can potentially be useful in its management. CGM data can be used as biofeedback to help support behavioural and lifestyle interventions, such as portion control and both timing and quality of food consumed. [14] Regular monitoring and feedback can encourage ownership and accountability to develop behaviours to help them stick to healthy weight management plans in the long-term.

Instances where CGMs are very limited in usefulness:
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‍Health and Wellness
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‍Healthy lifestyle changes, such as portion control, more activity, better sleep, and avoiding processed foods, are essential in delaying or preventing type 2 diabetes. If people without diabetes can monitor their glucose levels in real time and adjust behaviours when they go beyond a certain threshold, it could create a positive feedback loop to help maintain health.A study on individuals wearing a CGM for 10 days with use of a mobile app to track glucose, meal choices, heart rate and activity, showed significant improvement in glucose control over the ten days in both healthy individuals and those with pre-diabetes. [15] This suggests that CGMs could be beneficial in encourage healthier habits and reduce the risk of developing type 2 diabetes in at-risk individuals. The verdict is still out on this one though, as that was a small study and it’s results are not widely replicated.

Instances where CGMs are not helpful:
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‍Health Anxiety
‍Constant monitoring of glucose levels in response to food can lead to the avoidance of perfectly healthy foods (e.g., fruit) due to normal glucose rises. Excessive glucose monitoring also has the risk of unintentionally creating maladaptive dietary changes, such as excluding healthy carbohydrate-containing food to avoid glucose spikes (e.g whole grain bread), especially if the user does not understand what a ‘spike’ truly means.  It can also lead to increased anxiety around eating, leading to stress and potential disordered eating, such as orthorexia.

Giving Advise to Patients Asking About CGMs

‍With CGMs becoming more accessible, patients are going continue to ask about them. Instead of dismissing their curiosity, or being unaware altogether, here is a summary of some useful, evidence-based information to takeaway:

1. Reassure them that glucose variability is normal. Spikes aren’t inherently bad – what matters is the overall metabolic picture.
2. Encourage lifestyle-based interventions. Physical activity, balanced nutrition, and sustainable habits remain the best ways to support metabolic health. Focus on the essential building blocks of health, rather than imperfect metrics.
3. Discourage over-medicalisation. CGM use in non-diabetics can create unnecessary worry and an unhealthy fixation on glucose levels.
4. If a patient insists on using a CGM, help them interpret the data correctly. Trends matter more than individual readings, and the goal should be overall wellbeing, not chasing a ‘perfect’ glucose curve.

‍Final Thoughts: Is more knowledge always power?
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‍CGMs are an incredible innovation in diabetes care, but that doesn’t mean they’re useful for everyone.  It provides interesting and novel data, but is not clinically relevant in those without diagnosed conditions. It should also not be used as the sole basis for dietary changes, restrictions, or extreme lifestyle changes. Ultimately, just because we can measure something, doesn't mean we necessarily should.How can the SANNO platform help you using CGMs in your Practice:
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Interested in using CGMs beyond diabetes? With SANNO, your patients can connect their CGM on your SANNO app so you can easily track and interpret continuous glucose data alongside symptoms, nutrition, stress, and lifestyle factors — all in one place.

Our platform helps you spot patterns, personalise protocols, and improve outcomes by turning raw glucose readings into meaningful clinical insights for your non-diabetic patients.
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Escrito por la Dra. Julia Craggs, abril de 2025.

Referencias:
1] Barua S, Sabharwal A, Glantz N, Conneely C, Larez A, Bevier W, et al. Dysglycemia in adults at risk for or living with non-insulin treated type 2 diabetes: Insights from continuous glucose monitoring. EClinicalMedicine. 2021 May;35:100853.[2] Dehghani Zahedani A, Shariat Torbaghan S, Rahili S, Karlin K, Scilley D, Thakkar R, et al. Improvement in Glucose Regulation Using a Digital Tracker and Continuous Glucose Monitoring in Healthy Adults and Those with Type 2 Diabetes. Diabetes Therapy. 2021 May 28;12(7):1871-86.[3] Zeevi D, Korem T, Zmora N, Israeli D, Rothschild D, Weinberger A, et al. Personalized Nutrition by Prediction of Glycemic Responses. Cell [Internet]. 2015 Nov;163(5):1079-94. Disponible en: https://pubmed.ncbi.nlm.nih.gov/26590418/[4] Guess N. The growing use of continuous glucose monitors in people without diabetes: an evidence-free zone. Diabetes Práctica Internacional. 2023 Sep 1;40(5):19-9.[5] Klonoff DC, Nguyen KT, Xu NY, Gutierrez A, Espinoza JC, Vidmar AP. Use of Continuous Glucose Monitors by People Without Diabetes: An Idea Whose Time Has Come? Revista de Ciencia y Tecnología de la Diabetes. 2022 Jul 20;17(6):193229682211108.[6] Berry SE, Valdes AM, Drew DA, Asnicar F, Mazidi M, Wolf J, et al. Human postprandial responses to food and potential for precision nutrition. Nature Medicine [Internet]. 2020 Jun;26(6):964-73. Disponible en: https://www.nature.com/articles/s41591-020-0934-0[7] Hutchins KM, Betts JA, Thompson D, Hengist A, Gonzalez JT. Continuous glucose monitor overestimates glycemia, with the magnitude of bias varying by postprandial test and individual - A randomized crossover trial. The American Journal of Clinical Nutrition [Internet]. 2025 Feb; Disponible en: https://ajcn.nutrition.org/article/S0002-9165(25)00092-9/fulltext[8] Zhanna Oganesova, Pemberton J, Brown A. ¿Solución innovadora o motivo de preocupación? The use of continuous glucose monitors in people not living with diabetes: A narrative review. Diabetic medicine. 2024 Jun 26;[9] Ehrhardt N, Al Zaghal E. Behavior Modification in Prediabetes and Diabetes: Potential Use of Real-Time Continuous Glucose Monitoring. Revista de ciencia y tecnología de la diabetes. 2018 Aug;13(2):271-5.[10] Jackson MA, Ahmann A, Shah VN. Diabetes tipo 2 y el uso de la monitorización continua de glucosa en tiempo real. Diabetes Technology & Therapeutics. 2021 Feb 3;23(1).[11] Vivian Valeska Lelleck, Schulz F, Witt O, Kühn G, Klein D, Gendolla A, et al. A Digital Therapeutic Allowing a Personalized Low-Glycemic Nutrition for the Prophylaxis of Migraine: Real World Data from Two Prospective Studies. Nutrients [Internet]. 2022 Jul 17 [citado 2023 Apr 21];14(14):2927-7. Disponible en: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9315551/[12] Today Study Group. Long-Term Complications in Youth-Onset Type 2 Diabetes. New England Journal of Medicine. 2021 Jul 29;385(5):416-26.[13] Ishihara K, Uchiyama N, Kizaki S, Mori E, Nonaka T, Oneda H. Application of Continuous Glucose Monitoring for Assessment of Individual Carbohydrate Requirement during Ultramarathon Race. Nutrients. 2020 Apr 17;12(4):1121.[14] Liu K, Choi T, Zhao L, Xiao Tong Teong, Hutchison AT, Heilbronn LK. A qualitative exploration of behaviour change and maintenance experience in people with overweight or obesity in a dietary intervention. Nutrition & Dietetics. 2023 Dec 6;[15] Dehghani Zahedani A, Shariat Torbaghan S, Rahili S, Karlin K, Scilley D, Thakkar R, et al. Improvement in Glucose Regulation Using a Digital Tracker and Continuous Glucose Monitoring in Healthy Adults and Those with Type 2 Diabetes. Diabetes Therapy. 2021 May 28;12(7):1871-86.

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