The iLet Bionic Pancreas and “Diabetes Without Numbers”

There’s a new closed-loop insulin pump system available in the United States, one that is so simple to operate that its manufacturer is calling it a “bionic pancreas.” It’s the iLet, from Beta Bionics.

Compared to other looping systems, the iLet is radically simplified. There’s no carb counting, no basal rates, no correction factors — it delivers insulin automatically with almost no input at all from the user. It is, its creator Ed Damiano proclaims, “the first device that lets you manage your diabetes without numbers.”

Damiano, the founder of Beta Bionics, is a biomechanical engineer that years ago swore to build a better insulin pump when his infant son was diagnosed with type 1 diabetes. He spoke to Diabetes Daily about his invention.

Set It and Forget It

The iLet system begins by asking for a single input: your body weight. It does nearly everything else by itself, using lifelong machine learning.

The manual states: “You do not need to know your basal insulin rates, correction factors, or carbohydrate-to-insulin ratios to use the iLet.” In fact, if you do know your factors and ratios, it doesn’t matter, because you have no ability to input any of these numbers. There is no manual mode. The iLet takes all of these decisions out of your hands.

“The iLet determines 100 percent of every therapeutic insulin dose,” Damiano says. “That has never happened before. It’s not a hybrid closed loop system. It no world could you call it a ‘hybrid’ system.”

That makes the iLet a potentially ideal option for people that have never before used an insulin pump, or for people that struggle with all the math that diabetes requires. If you’ve never felt comfortable changing your own insulin ratios without the guidance of a doctor or diabetes educator, this might be your pump system because it does all the math and hides all the numbers.

Damiano states that it only takes about two days for the iLet to learn all of these factors. “It reaches its steady state within about 48 hours, on average.” It does this simply by guessing how much insulin you need and paying very close attention to how your body responds. Very soon, the software more or less knows how much basal insulin you need, how much insulin to use for meals, and how to adjust insulin delivery rates in response to low and high blood sugars.

The algorithm adapts adjusts so quickly that Damiano is confident that it can handle short-term changes in insulin sensitivity, including those associated with the menstrual cycle or illness.

No Carb Counting

Perhaps the most eye-popping feature of the iLet is a mealtime dosing system that doesn’t use carbohydrate counts.

Damiano calls carb-counting a “fiction.” He thinks that other insulin dosing systems that rely on carbohydrate counts are “participating in a shared fantasy.”

“People aren’t good at carb counting. Humans, as a species, can do amazing things, but they can’t count carbs, and we shouldn’t pretend they can.”

Instead, the iLet asks you to ballpark the carbohydrate content of your meal. For each meal, you can select from three different settings: “usual for me,” “more,” and “less.”

The iLet quickly learns your habits, and keeps breakfast, lunch, and dinner separate. If you usually eat a bowl of oatmeal for breakfast, eat your oatmeal and select a “usual for me” bolus. It should only take a few breakfasts for the iLet to learn how much insulin you need. Whether your regular lunch is a high-carb sandwich or a low-carb salad, the algorithm will learn and adjust.

“It’s all relative to you. Are you having a usual amount of carbs for you for that meal type, more, or less? That’s it.”

You can pre-bolus up to 15 minutes ahead of eating, but the manufacturer recommends that you use the “announce carbs” feature when the food actually arrives. The pump delivers the extra insulin at that instant, giving its best guess for three-quarters of the insulin that you’ll need to keep your blood sugar steady. It will react to highs and lows for the next several hours.

The system is so adaptive that if you forget to bolus, it would be a mistake to deliver a bolus after finishing your food. At that point, the corrections algorithm has already taken control of the situation, and your pump is already administering extra insulin to account for your rising blood sugar.

Blood Sugar Targets and Results

The iLet allows the user to choose from three blood sugar targets:


iLet glucose targets

That’s it. No numbers.

Of course, there are real numbers in the system. The “usual” setting, which most people use most of the time, sets a target blood sugar of 120 mg/dL. Changing the target to “lower” or “higher” changes the target by ± 10 mg/dL.

Damiano insists that the precise numbers are an unimportant distraction: “They mean absolutely nothing to you.” Setting a blood sugar target of 120 mg/dL will not allow you to achieve a blood sugar average of 120 mg/dL, because the insulin delivery algorithm is “much more punishing of blood sugar measurements below target than above target, as it should be. The iLet does everything it can to prevent hypoglycemia.” Other insulin dosing systems work the same way.

What matters instead are the results. In the pivotal trial that led to its approval, the iLet helped the average user achieve an A1C of 7.3 percent, approaching the standard recommendation of less than 7 percent for adults with type 1 diabetes.

This was an improvement for most trial participants, who enjoyed an average A1C drop of 0.5 percentage points and spent an additional 11 percent of their average day in range (+2.6 hours daily). There was no significant increase in the risk of hypoglycemia.

Damiano adds that frequent use of the “lower” and “higher” glucose targets can toggle these results up and down. Users could elect to stay on the “lower” blood sugar target continuously.

“On the iLet, if you switched from the lower to higher targets, you’d see about 15 mg/dL difference in mean glucose. That’s half a percent of A1C, that’s a huge difference!”

“Now that is useful information. That’s what you wanna know.”

The iLet is Not for Everyone

The iLet bionic pancreas is so radically streamlined that it may be a poor choice for the minority of people with type 1 diabetes that are already meeting or exceeding standard blood sugar targets. If, while reading this article, you find yourself wondering things like, “how do I bolus for protein?” or “how do I reduce my basal rate for exercise?”, you’re probably not the right customer for the iLet.

The simple answer is, you cannot do those things. There is no setting that lets users employ a more detailed management strategy. You’re completely in the hands of the system, for better or for worse.

There’s at least one situation where this approach really reveals its flaws: exercise. There’s no exercise setting, no reduced basal rate, and the algorithm is unlikely to adapt quickly enough to understand why your blood sugar is plunging during a jog.

I asked Damiano: If I’m about to go for a run, what do I do? His response: “One of two things. You can take some carbs before you exercise, or you can disconnect from the iLet.” Neither is a great solution. For some people with type 1 diabetes, that loss of control is likely to be a deal-breaker.

“This is for the 80 percent of people that aren’t meeting their A1C goals,” Damiano says. If your personal goal is an A1C better than 7 percent, he says, “don’t look to the iLet for that. That’s not what it’s designed to do.”

The results bear this out. Take a look at the following numbers from the iLet’s pivotal trial:

Users that began the trial with an A1C under 7.0 percent did not improve their control while using the iLet. But look at the results of trial participants that began the experiment with an A1C over 9.0 percent. They experienced exceptional improvement — an A1C reduction of 1.23 percent and an additional 6.8 hours per day spent in range.

To be fair, it’s possible that some users with an A1C of around 7.0 percent really appreciated the reduced cognitive burden granted by the iLet system, even if their blood sugar management didn’t much improve. But some might prefer the Omnipod 5, a system that similarly uses adaptive learning to develop insulin delivery rates, but offers slightly more control, including manual and exercise modes.

The iLet “is potentially for people with A1Cs around 7.0 who want to reduce the burden of care on themselves and get similarly good glucose control. But it’s not for the person who wants an A1C of 5.0,” Damiano says.

“It helps the people that need it the most.”

Simplicity at the Doctor’s Office

One of the inevitable consequences of the iLet’s “set it and forget” tech is that it minimizes the influence of healthcare providers. You don’t need an expert to help you review your blood sugar results and pump settings; the iLet is constantly and endlessly making all the adjustments you might need.

“Other systems rely on a physician programming an insulin regimen into your pump. We just use bodyweight.”

Damiano sees this as a huge bonus, liberating healthcare providers from all the messy mathematics of diabetes and providing a system that can be understood without specialized training.

“The reason it’s so important to us is that as soon as you ask physicians to deposit a healthcare and insulin regimen, like basal rates and correction factors, primary care cannot use those devices. It immediately excludes them. They’re too complicated.”

The only choice a physician has to make is to decide which of the three vague blood sugar targets they should recommend. “And,” Damiano says, “we’d even like to remove that from their plate. Why should your doctor have to choose the target?”

During follow-up visits, healthcare providers really only have two details to look at: Is the patient using the right glucose target? And are they using the meal announcement feature?

“It’s simpler to use than any device. That’s why we think it’s for the people. It’s the insulin delivery system for the people.”

Other Details

The iLet is a regular tubed pump, with an infusion set base that sticks to your body and a tiny cannula sits under the skin.

You load your iLet pump with glass cartridges that you have filled with NovoLog or Humalog fast-acting insulin. Beta Bionics is currently developing a line of pre-filled Fiasp cartridges that you can pop directly into the pump. Fiasp is an ultra-rapid insulin that could result in even better blood sugar numbers after the algorithm gets trained on it.
The pump is recharged with an inductive charging pad. The manual recommends charging for 15 minutes per day.
The iLet is rated waterproof to the IPX8 standard, which means it should be safe in a swimming pool.
The pump system requires a Dexcom G6 continuous glucose monitor (CGM) to work. Beta Bionics is working with Dexcom on integrating the G7.
If your CGM goes offline, the pump can continue operating, using what it remembers about your insulin requirements, for up to 72 hours. The pump will prompt you for a fingerstick blood sugar measurement every four hours.

iLet users would be wise to be trained and ready to switch to another method of insulin delivery, such as multiple daily injections, in case they lose access to their CGM for any reason.


The iLet is only the fourth closed-loop insulin delivery system approved for sale in the United States. It is currently approved for people with type 1 diabetes over the age of 6.

This system introduces a radically simplified approach to diabetes management, eliminating the need for precise carb counting, basal rates, and correction factors. The iLet may not be a great choice for people that like to keep tight control over their insulin usage, but it could prove to be a massive help for individuals who aren’t meeting their A1C goals.

The system is for sale now, though initially many clinics and insurers may be unfamiliar with it. If you’re interested, click “Get Started” on Beta Bionics’ website.

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