My mother was a dramatic woman, prone to overreaction. When I was a snotty teenager, I told her she needed to take several chill pills. Most of the time, I was right. But in 2004, as she swore in Korean and hurtled down the highway in a Honda Odyssey that had no business going 20 mph over the limit, swerving through traffic while I vomited bile into a plastic bag, I had to admit she was right to rush me to the emergency room.
After two days of nonstop vomiting, I thought I simply had a stubborn stomach bug. Instead, I watched doctors furrow their brows as I failed to keep down even tiny sips of water. They asked if I was diabetic. My mother said no—I was just on a ridiculous low-carb diet. Dizzy and disoriented, I was told to urinate on a strip of paper. It changed color. After that, things went blurry as the staff frantically worked to get me into a bed. I don’t remember much else, except waking up several hours and two full IV drips later to a doctor lecturing my mother about why unsupervised diets in teens can be dangerous.
In an ill-advised attempt to lose weight, I had accidentally created a situation where the ketones in my blood reached toxic levels—a condition called ketoacidosis.
That memory resurfaced when I heard last week that Abbott had received FDA authorization for a new continuous glucose monitor (CGM). The Libre Duo is the first two-in-one CGM that measures both glucose and ketone levels. For diabetics, understanding ketones is critical for the same reason I ended up in the ER roughly 22 years ago: ketoacidosis.
Diabetic ketoacidosis (DKA) occurs when there is not enough insulin to convert blood glucose into energy. The liver then turns to burning fat, and ketones are a byproduct of that process. That is not inherently harmful, but too many ketones cause blood to become highly acidic. In diabetics, this can happen alarmingly fast and can be fatal if left untreated. DKA is typically a concern in Type 1 diabetics, who do not produce enough insulin, but it can also occur in Type 2 diabetes, which develops over time, often due to lifestyle factors.
“It’s actually the most common hyperglycemic emergency for people living with diabetes. It’s the leading cause of hospitalization, and it’s increased quite rapidly over the last decade,” said Marc Taub, vice president of technical operations for Abbott’s diabetes care business. “The symptoms of rising ketones are easily missed—they’re a lot like a flu or infection.”
According to Taub, the new Abbott sensor measures beta-hydroxybutyrate—a type of ketone—and is intended to function like a “check engine light.” Worn for ten days at a time, the sensor monitors ketones in the background but will actively alert users when levels approach danger, much as CGMs do for glucose. The goal is to provide an actionable warning system that feels familiar to diabetics. It uses the same app, works with smartwatches, and allows caregivers to monitor the glucose and ketone levels of loved ones—a potentially major benefit, as DKA is a significant risk among diabetic children.
“DKA is one of the primary fears or dangers of uncontrolled or unmonitored diabetes,” said Dr. David Ahn, chief of diabetes at the Mary and Dick Allen Diabetes Center for Hoag Hospital. Ahn noted that ketone monitoring is much more common in children as part of standard diabetes education. “The overwhelming majority of adult clinicians, and even endocrinologists like myself, don’t routinely prescribe ketone strips … in a perfect world, [ketone strips] would be one of the things that we send patients home with. But in practical scenarios, it often just isn’t a top priority.”
Ahn also pointed out that ketone monitoring could be helpful in two specific treatment scenarios. The first is for insulin pump users, who face a higher risk of DKA because an undetected pump issue—such as a leak or connectivity problem—could inadvertently interrupt insulin supply and quickly lead to ketoacidosis. The second scenario is for diabetics taking SGLT2 inhibitors, a class of oral medications that help lower blood sugar by causing the kidneys to excrete excess glucose in urine.
“SGLT2 inhibitors are quite common, but they’re primarily a Type 2 diabetes drug,” Ahn said, adding that clinicians anecdotally find they help some Type 1 diabetics as well. “The problem is that our biggest clue that a patient has DKA is high blood sugar. When you’re taking an SGLT2 inhibitor, you have this uncommon pattern where your sugar might not be that high, but you can be in raging ketoacidosis.”
That, Ahn explained, has been the major reason the FDA has not yet approved SGLT2 inhibitors for Type 1 diabetics, even though the drugs could help control blood sugar. On paper, a two-in-one glucose and ketone monitor could act as a fail-safe, opening up new treatment options for Type 1 diabetics. Combined with helping diabetic children and insulin pump users, the technology should be a no-brainer—right?
Well, yes and no.
CGMs are an imperfect technology. Browse any diabetic subreddit, and you will find people who, while grateful for the peace of mind CGMs provide, worry about accuracy, data fatigue, and interpreting what their glucose levels mean. Look at discussions about the Libre Duo, and you will find plenty of Type 1 diabetics who are not sold. Some claim they have not needed to check ketones in over a decade. Others worry about false positives triggering disruptive alerts. (Having tested the Dexcom G7 for the past few weeks, I can confirm alerts can be quite loud.)
“I think it’s going to maybe be a rocky first year, or couple of years, but I’m also excited because I think we’re going to learn a lot. There’s so much we don’t know about ketone levels on a continuous basis,” Ahn said. “If you think about it, a ketone strip doesn’t even typically give you a number. It’s a color code of mild, moderate, and severe.”
This is one of the clearest examples of how wearable technology can be a double-edged sword. On one hand, the tech opens up a bigger picture of what is happening in the human body under a wide range of previously unmeasurable scenarios. That can be helpful for medical discoveries and for building a greater understanding of certain conditions than spot-check tests allow. It is why so many medical researchers see potential in using wearables. However, the challenge is tuning the massive amount of continuous wearable data to identify and draw a user’s attention to the correct signals.
Abbott’s Taub said the company worked with the FDA and clinicians to establish ketone performance standards for the Duo. But even among professionals, there is still a degree of guesswork when interpreting new data.
“There was a recent consensus statement published by top experts basically saying, ‘This is our guidance on ketone monitoring.’ They set a cutoff of 3 mmol/L. But even in that article—and I’ve talked to the authors of that article—that’s our best guess as to what numbers we should start worrying about,” Ahn explained. He added that factors like pregnancy, illness, fasting, and heavy exercise are all instances outside of DKA that could cause ketone levels to temporarily rise. “The medical community is a little anxious about understanding the signal-to-noise ratio. I think there’s going to be a lot of false positives.”
Eventually, the Duo sensor will likely follow a familiar wearable script. It will undoubtedly enable the medical community to learn a great deal more about ketones and DKA. The early stages will be bumpy, especially since wearable tech has a complicated relationship with accuracy. For now, Taub said the Duo requires a prescription, and Abbott has no immediate plans to expand access to over-the-counter applications. But it is not hard to see a scenario where, down the line, the Duo’s technology is marketed to a wider consumer base.
Metabolic tech is the new wearable frontier. Health tech startups increasingly want bodily fluids to measure metabolism. GLP-1 drugs are an ever more popular treatment. The public is experimenting with gray market peptides. The keto diet—which gets its name from ketones and where a metabolic state of fat-burning called ketosis is the ultimate goal—has been popular for close to twenty years. You do not have to be a genius to see how various consumer wearable companies could look at the Duo and see a new data field riddled with dollar signs. From there, it is not hard to see wellness influencers flattening a genuinely helpful technology as the “secret hack” the medical institution “doesn’t want you to know.”
This is, after all, what happened with CGMs.
The Duo makes me reflect on periods in my life where I was less wise. I ended up in the ER with ketoacidosis—a rare feat for non-diabetics—because I was a stressed-out teen lured into a fad diet by glossy magazines and celebrities wasting away in low-rise jeans. Would some version of the Duo have helped prevent that? The self-quantifying nerd in me says yes. The wearable expert in me suspects that, given my previous experiences with CGMs, I personally may have avoided an ER trip and instead spiraled into data obsession and then fatigue.
None of this is to say the Libre Duo is bad. Wearable tech is always a neutral tool with the potential to enable a lot of good—it just requires thought and discernment to be used in a truly healthy way. The thing is, the vast majority of people in their day-to-day lives will not need to monitor for ketoacidosis. When medical science adds another data set to our lives, it is important we ask why; that we understand what it actually tells us, and not just what we hope it says, or what we hope it can do for us.