Should Athletes Be Wearing a Continuous Glucose Monitor?
The research says it's complicated...
Walk into any gym, CrossFit box or even café these days and you'll likely spot one: a small sensor worn on the back of the arm, quietly reading glucose levels around the clock. Continuous glucose monitors (CGMs) were designed originally for people managing diabetes, but they've exploded in popularity among athletes, biohackers and health-conscious people who have never had a blood sugar problem in their lives.
The promise is compelling: real-time data on how your food, training and recovery affect your glucose levels, personalised to you. So, let's look at whether the evidence actually matches the hype. The answer, as with most things in nutrition science, is more nuanced than the marketing suggests.
What Is a CGM and How Does It Work?
A CGM is a small wearable sensor inserted just under the skin, usually on the upper arm, that measures glucose in the interstitial fluid (the fluid between your cells) every few minutes. It transmits this data to your phone in real time, giving you a continuous curve of glucose rises and falls throughout the day and night. For people with Type 1 diabetes, CGMs are genuinely life-changing. For athletes without diabetes, they're being positioned as a window into metabolic health and performance, but the two use cases are very different, and that distinction matters.
What Can You Learn From Wearing One?
There's a legitimate argument for CGMs as a short-term learning tool and here's what the research supports.
Individual glucose responses vary enormously. A 2024 review in Sports Medicine highlighted that CGMs can reveal meaningful differences in how individual athletes respond to the same foods, training sessions and recovery strategies, patterns that generic carbohydrate guidelines simply can't capture. Two athletes eating identical pre-match meals might show completely different glucose profiles, and that information could theoretically guide smarter fuelling decisions, both for the athlete and their coach.
Elite athletes show surprising glucose patterns.
A fascinating 2025 case study in Sensors (PMC) tracked elite athletes during record-breaking events and found glucose excursions well outside what we'd consider normal, including both hypoglycaemic (low) and hyperglycaemic (high) blood sugar swings, depending on exercise intensity, duration and fuelling approach. This suggests that extreme athletic demand creates a metabolic environment we don't fully understand yet, and that standard nutrition advice may not always account for it. As we say at Empowering Nutrition, "individualised, personalised nutrition is key".
Timing and fuelling gaps become much more visible. For athletes who regularly skip meals before training, go long periods without eating, or aren't sure whether their pre-session snack is actually doing anything, a CGM can make those patterns much more visible. Seeing a significant glucose drop 45 minutes into a session, or a rapid spike-and-crash after a particular meal, can be genuinely informative and, more importantly, motivating.
Where the Evidence Currently Falls Short
It's important as a nutritional therapist to provide an honest counterpoint, because looking at all angles of the research matters equally, not just for athletes but for everyone I work with.
Accuracy during exercise is reduced. This is perhaps the biggest practical issue. CGMs measure interstitial glucose, not blood glucose directly, and there can be a time lag between the two of typically 5 to 15 minutes. During exercise, when glucose is moving rapidly between compartments, this lag means the reading on your phone can be meaningfully different from what's actually in your bloodstream. A 2025 review in Performance Nutrition (Springer) concluded that this accuracy issue could limit the usefulness of CGM data specifically during training and competition.
There is currently no causal evidence that CGM use improves performance. Despite the growing popularity, no well-designed trial has yet shown that wearing a CGM and acting on its data actually makes non-diabetic athletes perform better. More investment and well-designed studies are needed before we can confidently support many of the claims being made about what CGMs can do for athletic performance.
CGMs can't measure what matters most for athletic performance. Interstitial glucose is one data point. It doesn't tell you about muscle glycogen levels (the primary fuel for high-intensity sport), carbohydrate flux, mitochondrial efficiency or any of the other metabolic variables that determine whether you perform well. As one review put it, a CGM is not a "fuel sensor," it's a glucose sensor, which is a narrower thing.
There is also a psychological cost to constant data (see my blog: "Who's In Charge — You or Your Wearable?"). Research on fitness wearables more broadly suggests that always-on biometric monitoring can increase anxiety, reduce flexibility around eating and training and decrease enjoyment of sport. If a CGM reading starts dictating your food choices in unhelpful ways, the tool may be doing more harm than good. The sporting bodies are watching too. The UCI (International Cycling Union), already prohibits CGM use during sanctioned races, raising questions about competitive fairness and whether real-time glucose data constitutes a form of technological assistance. It's an interesting discussion and one that touches on broader grey areas where technology and sport performance intersect.
So, Should You Consider Wearing One?
My honest answer: as a short-term experiment, yes, but as a long-term fixture, probably not.
If you've ever wondered why your energy crashes at the same point in a session, why you feel sluggish after certain meals, or whether your current fuelling strategy is actually working, a 7-to-14-day CGM trial can surface some really useful patterns. I've used it successfully with a number of clients, both athletes and recreational gym-goers and runners. I think of it less as a performance device and more as a diagnostic lens: a way to observe an individual's metabolic responses and have an informed conversation about what we're seeing together.
That's why I use CGM's from Glucose Evolution, which provides practitioner access to clients' real-time data alongside a full analysis of their food intake and activity. That context is everything. The data should never be viewed in isolation, because a reading that looks "unfavourable" on the surface may relate to food that is genuinely nourishing the client in other ways.
Where things become less useful and potentially counterproductive is when athletes start optimising in real time based on readings that may not be accurate during exercise, or when the data creates noise rather than clarity.
The research is clear that stable blood glucose, adequate fuelling around training and consistency in eating patterns are important for athletic performance. A CGM might help you identify where you're falling short on those fundamentals, but the fundamentals themselves are key and never change: nourishing food, conscious awareness of timing and a clear recovery strategy. That foundation remains, with or without a sensor on your arm.
The Bottom Line
CGMs are a genuinely interesting technology with real potential in athletic populations. They're best understood as a learning tool rather than a performance solution, and the data they produce needs knowledgeable, practitioner-led interpretation to be useful rather than overwhelming.
If you're curious about your glucose patterns and what they might mean for your training and energy, I work with athletes to make sense of exactly this kind of data and to build a nutrition strategy around what we find. I'm excited about what the future holds!
So get in touch to find out more!
References
Continuous Glucose Monitoring in Endurance Athletes: Interpretation and Relevance of Measurements for Improving Performance and Health — Sports Medicine, 2024
Beyond Euglycemia: Case Studies Using Continuous Glucose Monitoring in Elite Athletes Without Diabetes During Record Athletic Events — Sensors, 2025
Application Potential of CGM in Elite Endurance Athletes Without Diabetes: What Do Physiology and Current Evidence Tell Us? — Performance Nutrition, Springer, 2025
Continuous Glucose Monitoring Use in Athletes Without Diabetes — Gatorade Sports Science Institute
Will Continuous Glucose Monitoring Improve My Performance? USADA
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