In the middle of the night last June, Cindy Beckdam woke up to the sound of an unfamiliar alarm.
It was very loud, like an emergency alert, and it was coming from her phone.
More specifically, it was coming from a newly installed app connected to the glucose sensor implanted in her arm.
According to the app, her blood sugar dropped alarmingly low while she slept, triggering the alarm.
"So I got up in the middle of the night and ate a granola bar," she says.
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Continuous glucose monitors (CGMs), which monitor glucose levels in real time, have been used by millions of diabetics for years.
As a dietitian in Ontario, Canada, Beckedam installed one herself to better understand the technology for her diabetes patients.
But her trying two weeks became something of a cautionary tale.
"I was beside myself," she said.
"I actually asked myself, in the name of the world, do I have diabetes?"
She didn't have one.
After research, she discovered that her glucose levels were perfectly normal.
However, receiving constant updates on her blood sugar levels, without a medical condition requiring it, caused completely unnecessary fear.
"Well, that's where I think people could 'fall down the rabbit hole,'" she said.
These devices could soon be in the hands - or on the hands - of many more people, thanks to two recent US Food and Drug Administration (FDA) approvals for its widespread use.
This week, Abbott Laboratories said it has received federal approval for two over-the-counter CGMs, one of which is for people who do not have diabetes.
CGM use is already on the rise, with the distinctive "burns" on the arms that can be seen during morning commutes in major American cities.
But experts say that even if there's no proven harm from them, there's very little evidence that there's a need to spend huge sums of money — sometimes up to $300 a month — if you're not diabetic.
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Abbott's Lingo, which is a CGM for people without diabetes, is marketed to customers "who want to better understand and improve their own health and wellness."
It was one of the two FDA-approved devices for sale and is already available in the UK.
The FDA's 510 regulatory process evaluates medical devices for safety and efficacy, but marketing claims are not part of that evaluation.
"Understanding the glucose in your body is key to managing your metabolism so you can live a healthier and better life," Abbott's spokesman told the BBC.
Abbott said flattening the glucose curve can help improve energy, mood and sleep, and pointed to studies showing the impact of spikes in glucose levels on overall health, and the role of CGMs in managing them.
There is skepticism in the medical community about such claims, but one thing experts agree on is that CGMs have significantly improved the care of some people living with diabetes.
Type 1 diabetes is when a person's pancreas stops producing insulin, so regular injections are necessary.
Type 2 diabetes is more common and occurs when cells in the body become resistant to insulin and need more of it to keep blood glucose levels within the normal range.
It can usually be controlled with medication, diet, exercise and close monitoring, although some also take insulin.
Traditionally, diabetics monitored their blood sugar levels with finger prick tests, but CGMs can tell people with diabetes when their blood sugar is dangerously high or low, and whether insulin needs to be injected.
However, many experts say the evidence that CGMs improve the health of non-diabetics is virtually non-existent.
They insist that the devices are, at best, a distraction, and at worst, they can lead to dangerous fixations.
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An increasing trend
CGMs are big business.
Market leaders have estimated that sales will reach $20 billion worldwide in the next four years.
Earlier this year, the FDA approved the sale of an over-the-counter CGM made by Dekskom, intended for type 2 diabetics who don't use insulin but want to avoid regular finger prick tests.
And some new CGM start-ups, such as Signos, Nutrisens and Levels Helt, are now touting the prescription devices as something that can also be used as tools for energy, mood and metabolism.
The devices are becoming popular in the health, wellness and sports industries.
Dutch marathoner Abdi Nagije, who will compete in the Paris Olympics, told Reuters this week that he is wearing a CGM to try to better monitor the energy available in his own body.
Others, including some from the scientific community, have also expressed interest in the effects of glucose on metabolic health.
Nick Norwitz, 28, who graduated from Oxford University with a doctorate in nutrition and is currently in his fourth year of medical school at Harvard, said he believes CGMs can be powerful tools because glucose is "an indicator of what's going on hormonally." level in your body".
He studied their use while at Harvard and said he welcomes more research in the field.
Norwitz said he believes that in the long run, hormonal changes associated with frequent spikes in glucose can cause negative effects, including weight gain.
But, he added, glucose is only one measure and should not influence all health-related decisions.
"To be clear, I don't mean that if you eat a mango and your blood sugar spikes it's 'worse' for you than eating a plate of bacon," he says.
Interest in how CGMs can help you change your diet has also spiked in some parts of the internet.
Depending on your algorithm, a search for glucose monitors on TikTok or Instagram can land you dozens of testimonials from health and wellness influencers touting the technology's benefits.
One such influencer, Britney Bouchard, who promoted a particular CGM startup on her TikTok account and offered followers a discount code, said CGM helped her adjust her diet to reduce glucose spikes.
She received a percentage from the company when people bought a device through her link.
"I could feel the difference right away, in energy, sleep and brain fog," said Bouchard, a 41-year-old health instructor from Los Angeles.
According to her, the CGM showed her that her body was "unfortunately very, very sensitive to carbohydrates ... and even to fruit," she said, recalling that even after eating a pineapple she felt "nervous" and would felt sick.
"If I ate these, I'd feel tired within an hour."
A solution in search of a problem
And while some researchers and companies claim that CGMs can greatly benefit the average person, many in the scientific community are skeptical, citing a lack of evidence.
Glucose spikes are a symptom — not a cause — of diabetes, he says researcher from Oxford Dr. Nikola Ges.
She says there is no "benefit" to CGM for those who are not diabetic.
"Normally you would identify a problem and come up with solutions to fix it," she told the BBC.
"And this is the other way around. It's like we have the technology, and now we just have to find groups of people that we can convince that they need this technology."
The key issue experts stress is that it's surprisingly hard to find much data on what blood sugar patterns look like in people who don't have diabetes.
This makes it difficult to interpret the results of individuals in any meaningful way.
And most people's sugar will jump with fruit - a food group rich in vitamins and nutrients - but that's no reason to stop eating it.
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Dr. Ethan Weiss, a clinical cardiologist at the University of California, San Francisco, agrees that there is insufficient evidence that monitoring glucose levels in people without diabetes can measurably improve their health.
"I know of studies that show you can change your diet and you can reduce spikes in glucose. "I don't know of any studies that show that glucose monitoring actually has any benefits, in any significant way, like reducing your risk of disease," he said.
"I think that's what the devotees believe the most."
Dr. Weiss adds that he knows of no studies showing that CGMs are harmful.
Others, including Dr. Gess, say the potential for harm is real.
Instead of focusing on the cornerstones of health—things like regular exercise and a nutrient-dense diet—devices like CGMs encourage us to focus on the details of imperfect metrics.
And, in the worst case, they can create new problems, such as an eating disorder.
"It worries me that instead of doing simple things to improve our own health, we're turning meals into science experiments," she says.
"I get the impression that people have somehow forgotten what the purpose of life is."
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