3. Getting Started With Your APS

A helpful mindset to start with

It’s very common to feel overwhelmed when considering or trying out new technology. But having an open mind as you get started can help. Here are some tips as you get started:

It won’t be perfect, or easy, at first.

It will take time to adjust to the learning curve of your new APS. If you were on a pump before, you may remember the switch from MDI to pump. It wasn’t easy or perfect right away. It took time to adjust your settings. It took time to figure out all the features you could use.

The same will be true with your APS. You’ll start with the basics.

You’ll likely need to adjust your settings with the new system. It will take some experimentation and getting used to the system helping to “correct” for highs and lows. In fact, you may find yourself wondering why it gave more or less insulin... and then realize later why it did so. This learning period involves learning to trust the system, and also understanding its limitations. You will likely also learn from asking others about how or why the APS made the dosing decision that it decided was needed.

Expect it to get better over time, but expect to have to work in different ways.

It will likely take a little more work up front in order to achieve better outcomes, including the benefit of less work over time! You may spend more time at the beginning reviewing reports and adjusting settings. Many people find themselves asking “why am I high” or “why did I end up going low?” Sometimes it’s “just diabetes”. Other times you can identify where your manual actions may have counteracted the system’s attempts to do the most optimal thing.

When you go into automated insulin delivery mode, you have to figure things out again just like you did when you went on a basic pump. You need to be able to figure out what’s happening and why it’s doing what it’s doing, so if you’re not happy with what’s happening, you can make a change. Why are you running high? Why are you running low? Knowing why it’s doing what it’s doing is critical for adjusting – either tweaking the closed loop settings, if you can, or adjusting your own behavior. Especially in the first few cycles of new tech, you’ll have a lot of learning around “I used to do things like X, but now I need to do them like Y.”

Knowledge of your diabetes is the most important thing.

At the end of the day, even with automated insulin delivery, you’re in charge. If something doesn’t feel right, you can always stop (or pause) and switch back to manual mode. You should still be prepared to deal with, and treat, hypoglycemia. It will still happen. You may find over time, though, that you can treat low blood sugars with fewer carbs than before, if the automated system has been reducing your insulin delivery as your BG dropped over time. And similarly, you may still need to occasionally manually treat for hyperglycemia, but not as much as you would have before. And always, before taking manual correction, make sure you know how much insulin on board you have!

Switching to automated diabetes mode: autopilot for your diabetes

An artificial pancreas in any form of automated insulin delivery isn’t a cure. You still have diabetes. You still need to change your pump site. You still may have to calibrate your CGM sensor. You will still need to change your CGM sensor periodically. It’s very similar to “autopilot” for planes - especially because they still have a pilot. With an APS, you’re still around and piloting, even if you have automated help from the technology. You’re still in charge of flying the plane.

You can think of one CGM sensor session like a “flight”. You don’t loop (automate the insulin delivery) when you’re not wearing CGM or when you’re not getting sensor data, so inserting your CGM sensor is like getting ready in the “pre- flight” stage. Once you have CGM data going, you can “take off” and the system can start calculating and making adjustments. But if your CGM rips out or the session ends as planned, you’ll be back in manual mode until a new CGM session is started.

Pick a good time to start

When you run a race, one common piece of advice is not to run a race in new clothes, or with a new type of energy bar, etc. The same goes for getting started with an APS. Don’t turn on your APS right before a big presentation at work, the night before your marathon, etc.

Instead, plan to start your first APS session when you have a little bit of time. Why? Well first and foremost... it’s exciting! You should enjoy the feeling of switching to automated insulin delivery mode. But also, you’ll have questions and run into issues. It will take time to learn what you need to do differently, and to monitor the system. Having a little more time to focus, adjust to the new method of insulin delivery, and changing your behavior will make it less stressful.

What do you need to know before you start?

You’ll find me repeating comments about changing your behaviors. Some of your behaviors will change immediately, and more will change over time. Especially as it relates to first treating, and later preventing contributing to, hyper- and hypoglycemia.

As you start, make sure you know:

  • What is my BG target? When does it correct differently for hyper- and hypoglycemia? Is it a single target, or a range? How can I adjust the target, if at all? How can I adjust it for a short period of time vs. adjusting my regular target?

  • How do I bolus? Do I use the bolus wizard? What happens if I bolus on the pump or in the app? What happens if I don’t use the bolus wizard? Do I enter carbs for meals? What happens if I don’t enter carbs? What if I forget to enter or bolus for carbs? Should I enter carbs for hypoglycemia?

  • How do I know if the system is in automated mode? What do I do if it’s not automating insulin delivery? How do I turn it on/off if I need to? How do I know what it’s doing?

  • What does it know? What is it predicting will likely happen? Will it alert me if I need to take action?

  • How can I monitor it on a different display or device? What alarm controls do I have? Are my alarms for CGM glucose levels, or are there also predictive alerts and system status alarms?

  • When, and how, can I adjust my settings and preferences, or change which features I use?

Settings adjustments

One of the most frequent things people need to do when starting a closed loop system is adjust their settings. Many people are using settings that reflect the 10-years-ago-reality of their body’s insulin needs. Other people have tweaked things over time, and their settings are actually wrong in multiple (partially offsetting) ways, but somehow they’re getting ok outcomes. It’s hard - for both people with diabetes and healthcare providers - to adjust pump settings.

Historically, most people have guessed basal rates, ISF, and carb ratios. Their doctors may use things like the “rule of 1500” or “1800” or body weight. But, that’s all a general starting place. Over time, people have to manually tweak these underlying basals and ratios in order to best live life with type 1 diabetes. It’s hard to do this manually, and hard to know if you’re overcompensating with meal boluses (aka an incorrect carb ratio) for basal, or over-basaling to compensate for meal times or an incorrect ISF.

But this can be the difference between 70% and 90% time in range, and up to a percentage point difference in A1c. After all, an automated insulin delivery system uses your settings as a starting point for its calculations. For someone with reasonably tuned basals and ratios, that works great. But for someone with values that are way off, it means the system can’t help them adjust as much as someone with well-tuned values. It’ll still help, but it’ll be a fraction as powerful as it could be for that person.

We learned quite a lot about this in the early days of OpenAPS. We designed OpenAPS to fall back to whatever values people had in their pumps, because that’s what the person/their doctor had decided was best. However, we know some people’s settings aren’t that great, for a variety of reasons. (Growth, activity changes, hormonal cycles, diet and lifestyle changes – to name a few. Aka, life.) One of the most frequently asked questions was - and still is - about how to achieve better outcomes after the initial improvements from closed looping. And probably 90% of the time it comes down to adjusting the baseline settings.


In the DIY world, we ended up creating a tool called “Autotune”. Autotune is designed to iteratively adjust basals, ISF, and carb ratio over the course of weeks – based on a longer stretch of data. It draws on a large pool of data, and is therefore able to differentiate whether and how basals and/or ISF need to be adjusted, and also whether carb ratio needs to be changed. For safety, none of these parameters can be tuned beyond 20-30% from the underlying pump values. If someone’s autotune keeps recommending the maximum (20% more resistant, or 30% more sensitive) change over time, then it’s worth a conversation with their doctor about whether the underlying values need changing on the pump – and the person can take this report in to start the discussion.

Autotune was originally designed for use on OpenAPS rigs specifically, but the feedback was so positive and the demand was so high that the community worked to build ways to make it possible for anyone to run Autotune, even without an OpenAPS rig. This meant Loop & AndroidAPS users, as well as non-DIY closed loop users, could analyze their data and generate recommendations for how they might change their settings.

Now, it’s worth noting, that like the other DIY technologies, this is not an FDA-approved tool. However, it’s being used regularly by hundreds of individuals to adjust their settings. So if you either are already tracking CGM data in Nightscout, and are willing to add boluses/temp basals/carbohydrate data for a week, you can set up and run Autotune as well. It doesn’t matter which type of pump you have. (There have also been a few MDI users who have chosen to run it).

Manually adjusting settings - common patterns to watch for

If you can’t, or don’t want to use Autotune, there are still other ways to evaluate your settings. One of the most common issues is that people have their basal rates set too high, and then a low carb ratio or ISF to compensate. If you’re closed-looping and seeing lots of insulin reduction overnight, chances are your default basal rates may be too high. Similarly, around mealtime, if the system has to add a lot of insulin, your carb ratio may be too “weak”, and those basal rates too high.

Note: It’s very important to understand that you should only change ONE thing at a time, and observe the impact for 2-3 days before choosing to change or modify another setting (unless it’s obviously a bad change that makes things worse, in which case you should revert immediately to your previous setting). The human tendency is to turn all the knobs and change everything at once, but if you do so, then you may end up with further sub-optimal settings for the future, and find it hard to get back to a known good state.

Hills and valleys, peaks and troughs, up and down

Sometimes people observe “roller coasters” in their BG graph. Remember this is all relative - to different people, BG rising and falling by 20 points may or may not be a big deal (but a 50 point rise or drop might feel like a roller coaster).

First, you should eliminate human behaviors that cause these. Usually, it’s things like giving a traditional dose of “fast carbs” (such as 15g+ of sugar, glucose tabs, candy, etc.) that is more than needed for a low or a pending low, unless you have significant levels of insulin on board. Remember the system is reducing insulin, and so you often need way fewer carbs to deal with a low, so you may rise afterward if you do too large of a carb correction. Overcorrections like that generally can’t be fixed by changing settings: you have to also change behaviors. Ditto for human-driven drops, e.g. by rage bolusing or otherwise bolusing too much when BG is high.

Human behaviors set aside, if you are still seeing hills and valleys in your BG graphs, consider the following:

  • ISF may be off, so you may want to raise ISF to make corrections less aggressive. Remember, make small changes (say, 2-5 points for mg/dL, and .5 or less for mmol) and observe over 2-3 days.

  • If you’re seeing highs followed by lows after meals, your carb ratio (CR) may need adjusting. One common mistake is to compensate for rapid post-meal rises with a very aggressive CR, which then causes subsequent low BG. One tool for preventing meal spikes is setting an “eating soon” low temporary target before and/or right after a meal, to get more insulin started earlier, and then allow your APS to reduce insulin once the temp target expires, to help prevent a post-meal low. Similarly, a small manual “eating soon” bolus up to an hour before a meal, or a larger prebolus right before a fast-carbs meal, can help match insulin timing to carb absorption without increasing the total amount of insulin delivered (and subsequently causing a post-meal low).

It can be hard to adjust to the idea that your settings need to be changed. There can be some emotional ties or challenges with how much insulin you have been, or need to be taking. You may also have been told to have a certain percentage of basal compared to bolus insulin. However, many of the old rules and recommendations were developed decades ago, and are no longer relevant guidelines for optimizing settings.

The bottom line is that if you’re using an APS, expect to need to change your settings compared to what you were using before.

Last updated