FAQ for loopers

How to add questions to the FAQ: Follow the these instructions


Can I just download the AAPS installation file?

No. There is no downloadable apk file for AAPS. You have to build it yourself. Here’s the reason why:

AAPS is used to control your pump and give insulin. Under current regulations in Europe, all systems classed as IIa or IIb are medical devices that require regulatory approval (a CE mark) which needs various studies and sign offs. Distributing an unregulated device is illegal. Similar regulations exist in other parts of the world.

This regulation is not restricted just to sales (in the meaning of getting money for something) but applies to any distribution (even giving away for free). Building a medical device for yourself is the only way to use the app within these regulations.

That’s why apks aren’t available.

How to begin?

First of all, you have to get loopable hardware components:

Secondly, you have to setup your hardware. See example setup with step-by-step tutorial.

Thirdly, you have to setup your software components: AAPS and CGM/FGM source.

Fourthly, you have to learn and understand the OpenAPS reference design to check your treatment factors. The founding principle of closed looping is that your basal rate and carb ratio are accurate. All recommendations assume that your basal needs are met and any peaks or troughs you’re seeing are a result of other factors which therefore require some one-off adjustments (exercise, stress etc.). The adjustments the closed loop can make for safety have been limited (see maximum allowed temporary basal rate in OpenAPS Reference Design), which means that you don’t want to waste the allowed dosing on correcting a wrong underlying basal. If for example you are frequently low temping on the approach of a meal then it is likely your basal needs adjusting. You can use autotune to consider a large pool of data to suggest whether and how basals and/or ISF need to be adjusted, and also whether carb ratio needs to be changed. Or you can test and set your basal the old fashioned way.

What practicalities of looping do I have?

Password protection

If you don’t want your preferences to be easily changed then you can password protect the preferences menu by selecting in the preferences menu “password for settings” and type the password you choose. The next time you go into preferences menu it will ask for that password before going any further. If you later want to remove the password option then go into “password for settings” and delete the text.

Android Wear Smartwatches

If you plan to use the android wear app to bolus or change settings then you need to ensure notifications from AAPS are not blocked. Confirmation of action comes via notification.

Disconnect pump

If you take your pump off for showering, bathing, swimming, sports or other activities you must let AAPS know that no insulin is delivered to keep IOB correct.

The pump can be disconnected using the Loop Status icon on the AAPS Home Screen.

Recommendations not only based on one single CGM reading

For safety, recommendations made are based on not one CGM reading but the average delta. Therefore, if you miss some readings it may take a while after getting data back before AAPS kicks in looping again.

Further readings

There are several blogs with good tips to help you understand the practicalities of looping:

How can I safely and securely attach the CGM/FGM?

You can tape it. There are several pre-perforated ‘overpatches’ for common CGM systems available (search Google, eBay or Amazon). Some loopers use the cheaper standard kinesiology tape or rocktape.

You can fix it. You can also purchase upper arm bracelets that fix the CGM/FGM with a band (search Google, eBay or Amazon).

AAPS settings

The following list aims to help you optimize settings. It may be best to start at the top and work to the bottom. Aim to get one setting right before changing another. Work in small steps rather than making large changes at once. You can use Autotune to guide your thinking, although it should not be followed blindly: it may not work well for you or in all circumstances. Note that settings interact with one another - you can have ‘wrong’ settings that work well together in some circumstances (e.g. if a too-high basal happens to be at the same time as a too-high CR) but do not in others. This means that you need to consider all the settings and check they work together in a variety of circumstances.

Duration of insulin activity (DIA)

Description & testing

The length of time that insulin decays to zero.

This is quite often set too short. Most people will want at least 5 hours, potentially 6 or 7.


Too short DIA can lead to low BGs. And vice-versa.

If DIA is too short, AAPS thinks too early that your previous bolus is all consumed, and, at still elevated glucose, will give you more. (Actually, it does not wait that long, but predicts what would happen, and keeps adding insulin). This essentially creates ‘insulin stacking’ that AAPS is unaware of.

Example of a too-short DIA is a high BG followed by AAPS over-correcting and giving a low BG.

Basal rate schedule (U/h)

Description & testing

The amount of insulin in a given hour time block to maintain BG at a stable level.

Test your basal rates by suspending loop, fasting, waiting for say 5 hours after food, and seeing how BG changes. Repeat a few times.

If BG is dropping, basal rate is too high. And vice-versa.


Too high basal rate can lead to low BGs. And vice-versa.

AAPS ‘baselines’ against the default basal rate. If basal rate is too high, a ‘zero temp’ will count as a bigger negative IOB than it should. This will lead to AAPS giving more subsequent corrections than it should to bring IOB ultimately to zero.

So, a basal rate too high will create low BGs both with the default rate, but also some hours hence as AAPS corrects to target.

Conversely a basal rate too low can lead to high BGs, and a failure to bring levels down to target.

Insulin sensitivity factor (ISF) (mmol/l/U or mg/dl/U)

Description & testing

The drop in BG expected from dosing 1U of insulin.

Assuming correct basal, you can test this by suspending loop, checking IOB is zero, and taking a few glucose tablets to get to a stable ‘high’ level.

Then take an estimated amount of insulin (as per current 1/ISF) to get to your target BG.

Be careful as this is quite often set too low. Too low means 1 U will drop BG faster than expected.


Lower ISF (i.e. 40 instead of 50) meaning insulin drops your BG less per unit. This leads to a more aggressive / stronger correction from the loop with more insulin. If the ISF is too low, this can lead to low BGs.

Higher ISF (i.e. 45 instead of 35) meaning insulin drops your BG more per unit. This leads to a less aggressive / weaker correction from the loop with less insulin. If the ISF is too high, this can lead to high BGs.


  • BG is 190 mg/dl (10,5 mmol) and target is 100 mg/dl (5,6 mmol).

  • So, you want correction of 90 mg/dl (= 190 - 110).

  • ISF = 30 -> 90 / 30 = 3 units of insulin

  • ISF = 45 -> 90 / 45 = 2 units of insulin

An ISF that is too low (not uncommon) can result in ‘over corrections’, because AAPS thinks it needs more insulin to correct a high BG than it actually does. This can lead to ‘roller coaster’ BGs (esp. when fasting). In this circumstance you need to increase your ISF. This will mean AAPS gives smaller correction doses, and this will avoid over-correcting a high BG resulting in a low BG.

Conversely, an ISF set too high can result in under-corrections, meaning your BG remains above target – particularly noticeable overnight.

Insulin to carb ratio (IC) (g/U)

Description & testing

The grams of carbohydrate for each unit of insulin.

Some people also use I:C as abbreviation instead of IC or talk about carb ratio (CR).

Assuming correct basal, you can test by checking IOB is zero and that you are in-range, eating exactly known carbs, and take an estimated amount of insulin based on current insulin to carb ratio. Best is to eat food your normally eat at that time of day and count its carbs precisely.


In some European countries bread units were used for determination of how much insulin is needed for food. At the beginning 1 bread unit equal to 12g of carbs, later some changed to 10g of carbs.

In this model the amount of carbs was fixed and the amount of insulin was variable. (“How much insulin is needed to cover one bread unit?”)

When using IC the amount of insulin is fixed and the amount of carbs is variable. (“How many g of carbs can be covered by one unit of insulin?”)


Bread unit factor (BU = 12g carbs): 2,4 U/BU -> You need 2,4 units of insulin when you eat one bread unit.

Corresponding IC: 12g / 2,4 U = 5,0 g/U -> 5,0g carbs can be covered with one unit of insulin.

BU factor 2,4 U / 12g ===> IC = 12g / 2,4 U = 5,0 g/U

Conversion tables are available online i.e. here.


Lower IC = less food per unit, i.e. you are getting more insulin for a fixed amount of carbs. Can also be called ‘more aggressive’.

Higher IC = more food per unit, i.e. you are getting less insulin for a fixed amount of carbs. Can also be called ‘less aggressive’.

If after meal has digested and IOB has returned to zero, your BG remains higher than before food, chances are IC is too large. Conversely if your BG is lower than before food, IC is too small.

APS algorithm

Why does it show “dia:3” in the “OPENAPS AMA”-tab even though I have a different DIA in my profile?

AMA 3h

In AMA, DIA actually doesn’t mean the ‘duration of insulin acting’. It is a parameter, which used to be connected to the DIA. Now, it means, ‘in which time should the correction be finished’. It has nothing to do with the calculation of the IOB. In OpenAPS SMB, there is no need for this parameter any longer.


Why using min. 5h DIA (insulin end time) instead of 2-3h?

Well explained in this article. Don’t forget to ACTIVATE PROFILE after changing your DIA.

What causes the loop to frequently lower my BG to hypoglycemic values without COB?

First of all, check your basal rate and make a no-carb basal rate test. If it is correct, this behavior is typically caused by a too low ISF. A too low ISF looks typically like this:

ISF too low

What causes high postprandial peaks in closed loop?

First of all, check your basal rate and make a no-carb basal rate test. If it is correct and your BG is falling to your target after carbs are fully absorbed, try to set an ‘eating soon’ temp target in AAPS some time before the meal or think about an appropriate prebolus time with your endocrinologist. If your BG is too high after the meal and still too high after carbs are fully absorbed, think about decreasing your IC with your endocrinologist. If your BG is too high while COB and too low after carbs are fully absorbed, think about increasing your IC and an appropriate prebolus time with your endocrinologist.

Other settings

Nightscout settings

AAPSClient says ‘not allowed’ and does not upload data. What can I do?

In AAPSClient check ‘Connection settings’. Maybe you actually are not in an allowed WLAN or you have activated ‘Only if charging’ and your charging cable is not attached.

CGM settings

Why does AAPS say ‘BG source doesn’t support advanced filtering’?

If you do use another CGM/FGM than Dexcom G5 or G6 in xDrip native mode, you’ll get this alert in AAPS OpenAPS-tab. See Smoothing blood glucose data for more details.


Where to place the pump?

There are innumerable possibilities to place the pump. It does not matter if you are looping or not.


Looping can reduce the pump battery faster than normal use because the system interacts through bluetooth far more than a manual user does. It is best to change battery at 25% as communication becomes challenging then. You can set warning alarms for pump battery by using the PUMP_WARN_BATT_P variable in your Nightscout site. Tricks to increase battery life include:

  • reduce the length of time the LCD stays on (within pump settings menu)

  • reduce the length of time the backlight stays on (within pump settings menu)

  • select notification settings to a beep rather than vibrate (within pump settings menu)

  • only press the buttons on the pump to reload, use AAPS to view all history, battery level and reservoir volume.

  • AAPS app may often be closed to save energy or free RAM on some phones. When AAPS is reinitialized at each startup it establishes a Bluetooth connection to the pump, and re-reads the current basal rate and bolus history. This consumes battery. To see if this is happening, go to Preferences > NSClient and enable ‘Log app start to NS’. Nightscout will receive an event at every restart of AAPS, which makes it easy to track the issue. To reduce this happening, whitelist AAPS app in the phone battery settings to stop the app power monitor closing it down.

    For example, to whitelist on a Samsung phone running Android Pie:

    • Go to Settings -> Device Care -> Battery

    • Scroll until you find AAPS and select it

    • De-select “Put app to sleep”

    • ALSO go to Settings -> Apps -> (Three circle symbol in the top-right of the screen) select “special access” -> Optimize battery usage

    • Scroll to AAPS and make sure it is de-selected.

  • clean battery terminals with alcohol wipe to ensure no manufacturing wax/grease remains.

  • for Dana R/RS pumps the startup procedure draws a high current across the battery to purposefully break the passivation film (prevents loss of energy whilst in storage) but it doesn’t always work to break it 100%. Either remove and reinsert battery 2-3 times until it does show 100% on screen, or use battery key to briefly short circuit battery before insertion by applying to both terminals for a split second.

  • see also more tips for particular types of battery

Changing reservoirs and cannulas

The change of cartridge cannot be done via AAPS but must be carried out as before directly via the pump.

  • Long press on “Open Loop”/”Closed Loop” on the Home tab of AAPS and select ‘Suspend Loop for 1h’

  • Now nnect the pump and change the reservoir as per pump instructions.

  • Also priming and filling tube and cannula can be done directly on the pump. In this case use PRIME/FILL button in the actions tab just to record the change.

  • Once reconnected to the pump continue the loop by long pressing on ‘Suspended (X m)’.

The change of a cannula however does not use the “prime infusion set” function of the pump, but fills the infusion set and/or cannula using a bolus which does not appear in the bolus history. This means it does not interrupt a currently running temporary basal rate. On the Actions (Act) tab, use the PRIME/FILL button to set the amount of insulin needed to fill the infusion set and start the priming. If the amount is not enough, repeat filling. You can set default amount buttons in the Preferences > Other > Fill/Prime standard insulin amounts. See the instruction booklet in your cannula box for how many units should be primed depending on needle length and tubing length.


You can find the AAPS wallpaper for your phone on the phones page.

Daily usage


What to do when taking a shower or bath?

You can remove the pump while taking a shower or bath. For this short period of time you may not need it, but you should tell AAPS that you’ve disconnected so that the IOB calculations are correct. See description above.


Depending on your job, you may choose to use different treatment factors on workdays. As a looper you should consider a profile switch for your typical working day. For example, you may switch to a profile higher than 100% if you have a less demanding job (e.g. sitting at a desk), or less than 100% if you are active and on your feet all day. You could also consider a high or low temporary target or a time shift of your profile when working much earlier or later than regular, of if you work different shifts. You can also create a second profile (e.g. ‘home’ and ‘workday’) and do a daily profile switch to the profile you actually need.

Leisure activities


You have to rework your old sports habits from pre-loop times. If you simply consume one or more sports carbs as before, the closed loop system will recognize them and correct them accordingly.

So, you would have more carbohydrates on board, but at the same time the loop would counteract and release insulin.

When looping you should try these steps:

  • Make a profile switch < 100%.

  • Set an activity temp target above your standard target.

  • If you are using SMB make sure “Enable SMB with high temp targets” and “Enable SMB always” are disabled.

Pre- and post-processing of these settings is important. Make the changes in time before sport and consider the effect of muscle filling.

If you do sports regularly at the same time (i.e. sports class in your gym) you can consider using automation for profile switch and TT. Location based automation might also be an idea but makes preprocessing more difficult.

The percentage of the profile switch, the value for your activity temp target and best time for the changes are individual. Start on the safe side if you are looking for the right value for you (start with lower percentage and higher TT).


You can remove the pump to be ‘free’, but you should tell AAPS so that the IOB calculations are correct. See description above.

Drinking alcohol

Drinking alcohol is risky in closed loop mode as the algorithm cannot predict the alcohol influenced BG correctly. You have to check out your own method for treating this using the following functions in AAPS:

  • Deactivating closed loop mode and treating the diabetes manually or

  • setting high temp targets and deactivating UAM to avoid the loop increasing IOB due to an unattended meal or

  • do a profile switch to noticeably less than 100%

When drinking alcohol, you always have to have an eye on your CGM to manually avoid a hypoglycemia by eating carbs.


How can I loop during the night without mobile and WIFI radiation?

Many users turn the phone into airplane mode at night. If you want the loop to support you when you are sleeping, proceed as follows (this will only work with a local BG-source such as xDrip+ or ‘Build your own Dexcom App’, it will NOT work if you get the BG-readings via Nightscout):

  1. Turn on airplane mode in your mobile.

  2. Wait until the airplane mode is active.

  3. Turn on Bluetooth.

You are not receiving calls now, nor are you connected to the internet. But the loop is still running.

Some people have discovered problems with local broadcast (AAPS not receiving BG values from xDrip+) when phone is in airplane mode. Go to Settings > Inter-app settings > Identify receiver and enter info.nightscout.androidaps.

xDrip+ Basic Inter-app Settings Identify receiver


How to deal with time zone changes?

With Dana R and Dana R Korean you don’t have to do anything. For other pumps see time zone travelling page for more details.

Medical topics


If you want to share some information about AAPS and DIY looping with your clinicians, you can print out the guide to AAPS for clinicians.

Medical appointment with your endocrinologist


You can either show your Nightscout reports (https://YOUR-NS-SITE.com/report) or check Nightscout Reporter.

Frequent questions on Discord and their answers…

My problem is not listed here.

Information to get help.

My problem is not listed here but I found the solution

Information to get help.

Remind us to add your solution to this list!

AAPS stops everyday around the same time.

Stop Google Play Protect. Check for “cleaning” apps (ie CCleaner etc) and uninstall them. AAPS / 3 dots menu / About / follow the link “Keep app running in the background” to stop all battery optimizations.

How to organize my backups ?

Export settings very regularly: after each pod change, after modifying your profile, when you have validated an objective, if you change your pump… Even if nothing changes, export once a month. Keep several old export files.

Copy on an internet drive (Dropbox, Google etc) : all the apks you used to install apps on your phone (AAPS, xDrip, BYODA, Patched LibreLink…) as well as the exported setting files from all your apps.

I have problems, errors building the app.


I’m stuck on an objective and need help.

Screen capture the question and answers. Post-it on the Discord AAPS channel. Don’t forget to tell which options you choose (or not) and why. You’ll get hints and help but you’ll need to find the answers.

How to reset the password in AAPS v2.8.x ?

Open the hamburger menu, start the Configuration wizard and enter new password when asked. You can quit the wizard after the password phase.

How to reset the password in AAPS v3.x

You find the documentation here.

Build error: file name too long

While trying to build I get an error stating the file name is too long. Possible solutions: Move your sources to a directory closer to the root directory of your drive (e.g. “c:\src\AndroidAPS-EROS”).

From Android Studio: Make sure “Gradle” is done syncing and indexing after opening the project and pulling from GitHub. Execute a Build->Clean Project before doing a Rebuild Project. Execute File->Invalidate Caches and Restart Android Studio.

Alert: Running dev version. Closed loop is disabled

AAPS is not running in “developer mode”. AAPS shows the following message: “running dev version. Closed loop is disabled”.

Make sure AAPS is running in “developer mode”: Place a file named “engineering_mode” at the location “AAPS/extra”. Any file will do as long as it is properly named. Make sure to restart AAPS for it to find the file and go into “developer mode”.

Hint: Make a copy of an existing logfile and rename it to “engineering_mode” (note: no file extension!).

Where can I find settings files?

Settings files will be stored on your phone’s internal storage in the directory “/AAPS/preferences”. WARNING: Make sure not to lose your password as without it you will not be able to import an encrypted settings file!

How to configure battery savings?

Properly configuring Power Management is important to prevent your Phone’s OS to suspend AAPS and related app’s and services when your phone is not being used. As a result AAPS can not do its work and/or Bluetooth connections for sensor and Rileylink (RL) may be shut down causing “pump disconnected” alerts and communication errors. On the phone, go to settings->Apps and disable battery savings for: AAPS xDrip or BYODA/Dexcom app The Bluetooth system app (you may need to select for viewing system apps first) Alternatively, fully disable all battery savings on the phone. As a result your battery may drain faster but it is a good way to find out if battery savings is causing your problem. The way battery savings is implemented greatly depends on the phone’s brand, model and/or OS version. Because of this it is almost impossible to give instructions to properly set battery savings for your setup. Experiment on what settings work best for you. For additional information, see also Don’t kill my app

Pump unreachable alerts several times a day or at night.

Your phone may be suspending AAPS services or even Bluetooth causing it to loose connection to RL (see battery savings) Consider configuring unreachable alerts to 120 minutes by going to the top right-hand side three-dot menu, selecting Preferences->Local Alerts->Pump unreachable threshold [min].

Where can I delete treatments in AAPS v3 ?

3 dots menu, select treatements, then 3 dots menu again and you have different options available.

Configuring and Using the AAPSClient remote app

AAPS can be monitored and controlled remotely via the AAPSClient app and optionally via the associated Wear app running on Android Wear watches. Note that the AAPSClient (remote) app is distinct from the NSClient configuration in AAPS, and the AAPSClient (remote) Wear app is distinct from the AAPS Wear app–for clarity the remote apps will be referred to as ‘AAPSClient remote’ and ‘AAPS remote Wear’ apps.

To enable AAPSClient remote functionality you must:

  1. Install the AAPSClient remote app (the version should match the version of AAPS being used)

  2. Run the AAPSClient remote app and proceed through the configuration wizard to grant required permissions and configure access to your Nightscout site.

  3. At this point you may want to disable some of the Alarm options, and/or advanced settings which log the start of the AAPSClient remote app to your Nightscout site. Once this is done, AAPSClient remote will download Profile data from your Nightscout site, the ‘Overview’ tab will display CGM data and some AAPS data, but but may not display graph data, and will indicate that a profile isn’t yet set.

  4. To activate the profile:

  • Enable remote profile synchronization in AAPS > NSClient > Options

  • Activate the profile in NSClient remote > Profile After doing so, the profile will be set, and AAPSClient remote should display all data from AAPS. Hint: If the graph is still missing, try changing the graph settings to trigger an update.

  1. To enable remote control by the AAPSClient, selectively enable the aspects of AAPS (Profile changes, Temp Targets, Carbs, etc.) that you would like to be able to control remotely via AAPS > NSClient > Options . Once these changes are made, you’ll be able to remotely control AAPS via either Nightscout or AAPSClient remote.

If you’d like to monitor/control AAPS via the AAPSClient remote Wear App, you’ll need both AAPSClient remote and the associated Wear app to be installed. To compile the AAPSClient remote Wear app, follow the standard instructions for installing/configuring the AAPS wear app, except when compiling it, choose the AAPSClient variant.

I have a red triangle / AAPS won’t enable closed loop / Loops stays in LGS / I have a yellow triangle

The red and yellow triangles are a security feature in AAPS v3.

Red triangle means that you have duplicate BGs and AAPS can’t calculate precisely the deltas. You can’t close the loop. You need to delete one BG of each duplicated value in order to clear the red triangle. Go to BYODA or xDRIP tab, long press one line you want to delete, check one of each lines that are doubled (or via 3 dots menu and Delete, depending on your AAPS version). You may need to reset the AAPS databases if there are too many double BGs. In this case, you’ll also loose stats, IOB, COB, selected profile.

Possible origin of the problem: xDrip and/or NS backfilling BGs.

The yellow triangle means unstable delay between each BG reading. You don’t receive BGs every 5 min regularly or missing BGs. It is often a Libre problem. It also happens when you change G6 transmitter. If the yellow triangle is related to the G6 tansmitter change, it will go away by itself after several hours (around 24h). In case of Libre, the yellow triangle will stay. The loop can be closed and works correctly.

Can I move an active DASH Pod to other hardware?

This is possible. Note that as moving is “unsupported” and “untested” there is some risk involved. Best to try the procedure when your Pod is about to expire so when things go wrong not much is lost.

Critical is that pump “state” (which includes it’s MAC address) in AAPS and DASH match on reconnecting

Procedure I follow in this:

  1. Suspend the DASH pump. This makes sure there are no running or queued commands active when DASH loses connection

  2. Put the phone into airplane mode to disable BT (as well as WiFi and Mobile data). This way it is guaranteed AAPS and DASH can not communicate.

  3. Export settings (which includes the DASH state)

  4. Copy the settings file just exported from the phone (as it is in airplane mode and we do not want to change that, easiest way is using USB cable)

  5. Copy the settings file to the alternate phone.

  6. Import settings on the alternate phones AAPS.

  7. Check the DASH tab to verify it is seeing the Pod.

  8. Un-suspend the Pod.

  9. Check the DASH tab and confirm it is communicating with the Pod (use the refresh button)

Congratulations: you did it!

Wait! You still have the main phone thinking it can reconnect to the same DASH:

  1. On the main phone choose “deactivate”. This is safe because the phone has no way of communicating with DASH to actually deactivated the Pod (it is still in airplane mode)

  2. Deactivation will result in a communications error - this is expected.

  3. Just hit “retry” a couple of times until AAPS offers the option to “Discard” the Pod.

When Discarded, verify AAPS is reporting “No Active Pod”. You can now safely disable airplane mode again.

How do I import settings from earlier versions of AAPS into AAPS v3 ?

You can only import settings (in AAPS v3) that were exported using AAPS v2.8x or v3.x. If you were using a version of AAPS older than v2.8x or you need to use setting exports older than v2.8x, then you need to install AAPS v2.8 first. Import the older settings of v2.x in v2.8. After checking that all is OK, you can export settings from v2.8. Install AAPS v3 and import v2.8 settings in v3.

If you use the same key to build v2.8 and v3, you won’t even have to import settings. You can install v3 over v2.8.

There were some new objectives added. You’ll need to validate them.