A Continuous Glucose Monitor Led to Kristen Faulkner’s DQ. Can They Really Help With Racing? (2025)

By now, most cycling fans have seen the headlines about Kristen Faulkner’s disqualification from the Strade Bianche road race. Faulkner finished in an impressive third place, but when officials spotted a continuous glucose monitor (CGM) patch on her arm, they disqualified her from the race.

Use of CGMs in racing is currently not allowed under UCI rules, though they’re fine to use in training. In Faulkner’s case, she was wearing the monitor but it wasn’t transmitted during the race—a distinction that the UCI officials decided still wasn’t enough to keep her third-place finish on the books. So why are cyclists, like Faulkner, so keen to use these glucose monitors? Can they really give an advantage that means they shouldn’t be worn in races? Here’s what to know.

What is a continuous glucose monitor (CGM)?

A CGM is a quarter-sized disk that you insert into the back of your arm, and it lasts for about two weeks. “On the inside of the disk is a tiny little filament, and that goes inside your skin to measure your glucose levels,” explains Catherine Staffie, a registered dietitian and nutrition manager at Nutrisense, a company that blends CGM usage with registered dietitian consultations within the app. “Traditionally, these have been used by diabetics in order to dose their insulin. But we believe glucose is a key health marker for anyone. Being able to use a CGM without a diabetes diagnosis has been life changing for so many people."

One of the biggest benefits of the CGM is that you get to see how your body is responding to what you eat, but also to your life. Exercise, sleep, and stress all can impact your glucose levels, and a CGM can be a way to see what’s going on internally. (That call from your boss might be causing more of a reaction than a hard threshold interval!)

“What’s so fascinating is that not only are you able to use that glucose data to say, ‘Wow, just having a donut for breakfast wasn’t a great idea,’” says Staffie. “You can also see that, ‘Wow, that was a stressful work call, and my glucose shot up from it.’ You can see that a workout wasn’t properly fueled because it caused a glucose spike and then a drop. This data can be applied to four pillars of health: nutrition, exercise, sleep, and stress. We can extrapolate out from the CGM data all of these really important pillars of health.”

Why would someone worry about glucose?

“Glucose is an energy source that is important for so many different functions in the body, and everyone has an individual response to different kinds of situations,” explains Kristina Skroce, a sport physiologist at Supersapiens, who started her work with cyclists and CGMs with Team Novo Nordisk working with riders who were using the technology to manage type 1 diabetes. “The visibility from a CGM gives us the possibility to know our bodies in a new way.”

As the body and brain’s primary energy source, glucose is important, and the more stable our blood sugar levels, the better our health outcomes. This doesn’t mean that your blood sugar should always be a flat line: It will spike when you have a meal, but it can also spike or drop from those lifestyle factors of exercise, stress, or sleep. Frequent spikes can lead to outcomes like an increased risk of type 2 diabetes and heart disease, as well as more day-to-day annoyances, like drops in energy or brain fog that can come after a spike.

While many of us generally know the best practices for eating healthily, our individual reactions to certain foods can vary hugely. One type of carbohydrate can cause a major spike, while another might have a more gentle rise. A CGM can show you how you respond to different foods, as well as different eating situations. Eating a slice of pizza during a working lunch where you’re arguing with coworkers may cause an entirely different reaction in your body than the same piece of pizza eaten mindfully and calmly in your office.

What are the benefits of CGM use for athletes?

First and foremost, using CGMs in training/everyday life, and in non-UCI races, is absolutely legal. (That’s important to note, in case there was any confusion after Faulkner’s DQ.) Riders are using CGMs primarily for training purposes, to see how certain fueling practices around rides (before, during, and after) influences their blood glucose levels. They can also see how exercise affects their blood sugar, and make lifestyle adjustments like shifting meal composition in order to maintain more stable blood sugar levels throughout the night.

It’s not just Faulkner who’s using a CGM in training. Prominent racers like Chris Froome, Wout van Aert, and many riders on Jumbo Visma use them for training, as do several top American racers, including gravel pro Lauren De Crescenzo. While many athletes will use SuperSapiens, a CGM platform designed specifically with athletes in mind—and that has the capability of “talking” to your cycling computer to remind you to eat—there are several brands available in the U.S. (SuperSapiens is not), including Nutrisense and Levels, that also offer CGM technology with an accompanying app.

Dialing in nutritional needs for different situations throughout training can be helpful. “I was surprised to learn about my body’s response to the heat. I’ve learned high temperatures can cause blood vessels to dilate, enhancing insulin absorption, and causing drops in blood sugar. I eat and drink much more during the summer months than during the winter and off-season,” says De Crescenzo.

A CGM can also reinforce the idea of avoiding emulating your teammates, because it turns out, what works for your friend may not work for you. “I’ve discussed CGM use with my teammate as we both use the Supersapiens CGM. Through our CGM use, we’ve both learned we need to start carb-loading in the days leading into a race. It’s impossible to top off our glycogen stores the night before a race,” says De Crescenzo. “But overall, we’ve learned that our metabolisms process foods differently and there is no one-size-fits-all nutrition approach to racing and training.”

“The problem with traditional fueling guidelines for training is that they’re super generalized,” adds RootED Nutrition and Counseling’s Caroline Burkholder, MS, RD, LD. “We say to take in 60 to 90 grams of carbs per hour when training, but if you can tolerate more, that’s often going to be better for you. A CGM can show you just how fast you burn through your fuel. If you drink a bottle of sports drink with 90 grams of carbs, a CGM can show you how quickly you burn through those carbs when you’re doing an effort. You may realize that after 30 minutes, your blood sugar is already back down to normal, and that means you may need to be fueling with more carbs to keep your energy levels high. This is where that hard data can be really useful.”

Do CGMs specifically help women athletes?

After her disqualification, Faulkner went on the record saying that CGMs could be extremely beneficial for female cyclists in particular. “It’s much more complicated for women than it is for men because we burn different amounts of fat versus glucose throughout the month, depending on where we are in our [menstrual] cycle,” she told Rouleur.“The second thing is that the risks for women of not getting it right are much deeper. If a man doesn’t fuel properly, he bonks, but if a woman doesn’t fuel properly, she could lose her period. That creates a whole host of hormonal deficiencies.”

“For women who have a menstrual cycle, who are going through perimenopause or who are dealing with PCOS (polycystic ovarian syndrome), there’s a huge hormonal element to how the body responds to different stressors that CGMs may shed light on,” Staffie agrees. “Throughout the different times of a woman’s cycle, she can see how receptive her body is to certain carbohydrates.”

Staffie adds that she’s seen women who struggle with irregular cycles use the CGM to inform shifts like stopping an intermittent fasting regimen. For many women, especially those with irregular cycles, the currently-trendy practice of eating only in a small window of time can lead to larger dips and spikes in their blood sugar throughout the day. Staffie notes that using the CGM to see these dips and spikes has helped women see the difference between a day of intermittent fasting versus eating throughout the day, and have shifted their habits—specifically, no longer fasting—to keep their blood sugar more stable.

Research around glucose, metabolism, and the menstrual cycle bears out these benefits. Regulating glucose and improving nutrient timing throughout the day may positively affect women athletes, particularly those who suffer from irregular cycles. The more often a woman becomes hypoglycemic (when blood sugar has dropped), the more likely she is to deal with menstrual irregularities, thanks to the stress response that comes with the drop. And it’s not just about how many calories an athlete eats during the day: The timing matters when it comes to hormonal health and avoiding health problems associated with Relative Energy Deficiency in Sport (RED-S).

In recent years, research has come out that suggests during different phases of the menstrual cycle, there are certain benefits and limitations. For example, Dr. Stacy Sims, the leading researcher on the topic of women in sport, has said that during the luteal phase, women can expect to have a harder time with interval workouts and ideally would focus on aerobic efforts.

But, Sims also acknowledges that race days don’t always track with menstrual cycles. You can’t change the date of your big race to correspond neatly with a certain hormonal phase. But, Staffie says, by assessing the data from the CGM and using it to see how your cycle influences your ability to process carbohydrates, you can at least optimize your macros for race day based on the data you’ve collected. Then, the more dialed in your fueling, the more likely you have a better performance.

Even looking beyond the menstrual cycle and the potential physical health values a CGM may provide, there may be another use case for female athletes in particular. Some statistics suggest that up to 45 percent of female athletes will struggle with an eating disorder or disordered eating.

In the cycling world, there’s significant emphasis on power-to-weight ratio, and many opt to focus on the weight metric to their own detriment. But there is potential for the objective data from a CGM to help an athlete look dispassionately at their nutrition and make decisions based on fueling needs, rather than continuing with less healthy behaviors that leave them underfueled and at risk for RED-S.

“What initially sparked my interest in CGM use is my history of eating disorders throughout my youth,” says De Crescenzo. “I ran cross-country in high school and for me, it was much easier to get away with not eating or drinking. I used to think being skinny was the key to success, but instead, it led to injuries and spending all my energy obsessing over my weight. Now with the CGM, I’m eating more than I have in my entire athletic career. The CGM helps me see my body in the lens of athletic performance and I’m not just hoping for a lower number on the scale.”

The amount of food an athlete needs in order to maintain physical health can be surprising. “I’ve struggled to fuel for these long gravel races and I attribute at least some of it to my previous distorted relationship with food,” De Crescenzo adds. “My first experience using the CGM was eye-opening and it felt like a window into my metabolism—I could see how fast I was processing carbohydrates and how much more rapidly I needed to be replenishing them. I previously laughed at my coach when he told me I wasn’t eating enough carbohydrates, but now they’re the staple of my diet! It turns out my body needs a lot of carbohydrates to fuel my racing and training.”

“I think people have such a low trust for what they need in terms of carbohydrates and calories in general,” says Burkholder. “I think a CGM can reassure them that they can actually follow their hunger cues, and that’s helpful. I think a lot of people, especially women athletes, sincerely believe that they are gluttons, that they overeat constantly. But in reality, often they’re not eating enough! Seeing the data on the CGM can be reassuring and show them objectively that they need that fuel.”

So, why did the UCI ban continuous glucose monitors?

That all sounds pretty innocuous, so why are CGMs banned by the UCI? They’re allowed in other sports—including Ironman triathlon—but the UCI has always tended to be a bit on the tech-phobic side.

In 2021, the UCI added the ban on CGMs in racing to their rule book, and since banning the tech, they’ve never clearly explained their reasoning. (Article 1.3.006 of the UCI regulations states: “devices which capture other physiological data, including any metabolic values such as but not limited to glucose or lactate are not authorised in competition.”)

As EF Education–EasyPost’s manager Jonathan Vaughters put it, “If they can’t understand’ it, they ban it.” And considering in 2018, UCI president David Lappartient actually supported a motion to ban power meters in racing to “preserve attractiveness of sport,” it’s not really that shocking that CGM tech would be off the table.

Are there risks to using a CGM?

While some people with a history of eating disorders will find CGMs to be useful tools to show them that eating more is only going to be beneficial, there are some people who will have the opposite experience. There is potential for the continuous monitoring to add mental stress and anxiety around “good” versus “bad” food.

“Anyone who has struggled with an eating disorder in the past or is currently struggling with disordered eating may find that a CGM is more triggering than helpful,” says Staffie. “If this is a triggering device or app, we do not recommend the CGM.”

This is also why it’s important to work with a dietitian or other expert, like a psychologist, who can help you when you feel like the data brings on disordered eating habits or when you need some guidance on what you do with the data to make healthy changes.

Also, because other stressors influence your blood sugar, beyond food, the readings can be frustrating for someone who tend toward disordered eating behaviors. “Oftentimes, there are aberrations that aren’t really well explained,” says Burkholder. “You run the risk of becoming very frustrated, thinking that you’ve done something wrong to cause your blood sugar to be less stable than it normally is, but it’s natural. So I think that's important to note if you know you can become punitive or overly critical of your behaviors, it’s very possible this data could make that worse.”

On that note, no matter who you are, beware the temptation to read too obsessively. Even De Crescenzo admits that while it’s helped her improve her relationship with food, it can feel like data overload. “As a self-professed data nerd, being able to see real-time glucose data can be overwhelming. At the end of the day, there can be too much of a good thing,” she admits. That’s why she switched some of her settings to get frequent, but not on-the-minute, readings.

While early research is incredibly promising and anecdotal evidence for the benefits of CGM use for elite athletes is mounting, it’s important to understand that there are still other limitations to the technology.

“A lot of things still need to be studied, discovered and confirmed. We need to build up the research, but we are working in that direction rapidly,” Skroce says. Because her background is as a research scientist, she’s quick to point out that while she hears from athletes who are making positive changes based on CGM use, there isn’t much published, peer-reviewed research yet on CGM use in healthy populations. Research on women in particular is lacking, she adds.

But that’s beginning to change. Researchers have released studies—and continue to conduct studies—on healthy populations and on athletes in particular based on CGM usage, with more (hopefully) on the way. Additionally, we are seeing more research done on women athletes looking at how factors like blood sugar, in addition to menstrual cycles, affect training and general health.

For interested athletes, the biggest limiter is likely the cost. In fact, that’s a big part of why Faulkner didn’t take hers off to race. She wasn’t using the information during the race, but removing the CGM for every race (often two per week during the season) would be incredibly pricey.

Most companies that provide CGM hardware and software to healthy populations charge between $200 and $300 per month, which includes the CGMs themselves. The sensors will last for about two weeks, but they can’t be removed and reinserted, and replacing them adds up to more dollars.

What else should you know about CGMs?

Right now, the options in the U.S. are limited to more health-focused CGMs rather than the athlete-focused Supersapiens version, which not only has a phone app, it can also sync to your Garmin or Wahoo computer for in-ride readings. For anyone who wants to test out a Supersapiens CGM, unfortunately, the tech is only available to consumers in Europe, though the brand is hoping to bring it stateside soon.

If you do decide to try out a CGM, remember that if you just set it and forget it, it won’t do anything for you. As with any wearable, it’s only as good as your ability to parse the objective data with your subjective feeling and what was happening throughout the day to cause the valleys and troughs in your readings. If you aren’t using the apps to make notes of certain meals or stress-filled moments, it’s hard to pull insights from them.

And remember: No app can be a substitute for developing an understanding of how you feel. “We’ve come so far with all the data that we can collect and measure today,” says Skroce. “But what is really important is that you feel good. And hopefully, that is in line with your data. I am a scientist, so I love the data. But I’m also a coach, and so from the practical standpoint, I know that we cannot just look at the data and say something is good or bad without considering how an athlete actually feels.”