Your AAPS profile

Your AAPS Profile is a set of four key parameters which define how AAPS should deliver insulin in response to your sensor glucose levels. These are the main parameters AAPS is built upon. As you progress through the Objectives, you will unlock additional modifiable parameters (like SMB settings), but the performance of these features rely on your underlying Profile being correct. The Profile incorporates:

• glucose targets,

• basal rates (BR),

• insulin sensitivity factors (ISF) and

• insulin-to-carb ratios (IC or ICR).

Where did DIA go?

The duration of insulin action (DIA) is no longer part of your Profile. It is set per insulin instead — see Manage → Insulin settings.

As part of AAPS’ management, users should continually assess and scrutinize the accuracy of their Profile settings. It is recommended to take the settings in the order they are presented here. Aim to get one setting right before changing another. Work in small steps rather than making large changes at once. Don’t forget to activate the new profile after each change. Regularly back up your Profile settings by exporting your settings.

Your Profile settings interact with one another - you can have ‘wrong’ settings that work well together in certain circumstances but do not in others. For instance, if a too-high basal happens to be at the same time as a too-high CR. This means that you need to consider the settings individually and check they work harmoniously together in a variety of circumstances.

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.

Your diabetes may vary

Profiles vary significantly from person-to-person.

For basal rates (BR), insulin sensitivity factors (ISF) and insulin-to-carb ratios (IC or ICR), the absolute values and trends in insulin requirements vary significantly from person to person, depending on your biology, gender, age, fitness level etc. as well as shorter term factors like illness and recent exercise. For more guidance on this, the book “Bright Spots and Landmines” by Adam Brown is an excellent book to read.

The four last parameters (glucose targets, basal rates, insulin sensitivity factors and insulin-to-carb ratios) can be set to different values, changing hourly if required, over a 24-hour period.

Screenshots from AAPS of an example profile are shown below. Please note, this sample profile below shows a large number of timepoints. When you start out with AAPS, your profile is likely to be much simpler.

Glucose targets

Description

Your BG target is a core value and all of AAPS calculations are based on it. It is different from the target range which you usually aim to keep your blood glucose values in. The target is used in AAPS calculations: if AAPS predicts that your BG will land outside the target range, then it will take action to take you back in said range.

The targets can be defined within those boundaries :

	Low target	High target
Minimum	4.4 mmol/L or 80 mg/dL	5 mmol/L or 90 mg/dL
Maximum	10 mmol/L or 180 mg/dL	11.1 mmol/L or 200 mg/dL

Impact

If the target in your Profile is very wide (say, 3 or more mmol/L [50 mg/dL or more] wide), you will often find little AAPS action. This is because BG level is predicted to be somewhere in that wide range, and thus temporary basal rate are unlikely to be actioned by AAPS.

How to set it

The figure below shows an example of how the target can be set in an AAPS profile.

BG targets are set according to your personal preferences and requirements. For example, if you are concerned about hypos at night, you may set your target slightly higher at 117 mg/dL (6.5 mmol/L) from 9 pm - 7am. If you want to make sure you have plenty of insulin on board (IOB) in the morning before bolusing for breakfast, you may set a lower target of 81 mg/dL (4.5 mmol/L) from 7 am - 8 am.

When In Open Loop, especially when progressing through the first objectives, using a wide range target can be a good option while you are learning how AAPS behaves and adjusting your Profile.
When In Closed Loop (starting at Objective 6), it is recommended to reduce the range until you have a single target for each time of the day (Low target = High target), to make sure that AAPS reacts promptly to BG fluctuations.

Basal rates

Description

Your basal rate of insulin (Units/hour) provides background insulin, keeping your glucose levels stable in the absence of food or exercise.

The insulin pump delivers small amounts of rapid acting insulin every few minutes, to keep the liver from releasing too much glucose, and to move glucose into body cells. Basal insulin usually makes up between 40 - 50% of your total daily dose (TDD), depending on your diet, and typically follows a circadian rhythm, with one peak and one valley in insulin requirements over 24 hours. For more information, chapter 6 of “Think like a Pancreas” by Gary Scheiner is very useful.

Most type 1 diabetes educators (and people with type 1 diabetes!) agree that you should work on getting your basal rates correct, before attempting to optimize your ISF and ICR.

Impact

Accurate basal rates enable you to wake up in range, and to skip meals - or eat - earlier or later in the day, without going high or low.

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.

How to set it

The figure below shows an example of how the basal rates can be set in an AAPS profile.

Setting your basal rates right is done by trial and error, and should be done in consultation with your diabetes team.

There are basal testing methods which usually entails observing your basal rates and insulin needs during an intermittent fasting over a 24-hour period. Although you need to test your basal rates for the whole day, it is not recommended to fast during 24h straight. This is because the body triggers mechanisms such as hormones to compensate. A recommended way is to fast over 3 different days for a period of 8 hours.

The recommended method is to suspend the loop (for safety you can set AAPS to LGS to avoid lows, as done for achieving objective 6), which will revert to your default background basal rate. Observe how your BG changes: if it is dropping, basal rate is too high. And vice versa.
An alternative method (may be more tricky) is to keep the loop running, and seeing how IOB changes. If IOB is negative, your basal rate is too high. And vice versa. Beware that this method relies on ISF to correct BG, and thus depends on other variables to be set reasonably well for it to be successful.
Another way of adjusting your basal rates is to watch the loop action during the night, when all COB have decayed. This method is particularly useful for children, when fasting is difficult or insulin needs change often. Dr Saleh Adi from Tidepool provides useful ways on how to analyze overnight BG lines in order to optimize your basal rates.

See here how to tweak your basal profile, analyzing patterns in closed loop.

When taking action on the result of your basal testing, changes in the Profile should be done 1 to 2 hours (depends on your insulin type) before the rise/drop. Repeat the test as necessary until you are comfortable with your basal rates settings.

Message: “Basal rate is not compatible with the current pump”

Each pump has limits: a lowest and a highest basal rate it can deliver and, for some pumps (for example Dana, Accu-Chek Combo, Medtronic and Diaconn G8), basal rates that can only change on the full hour. AAPS checks your profile against the pump you use, after applying the percentage you choose.

If a basal rate is outside these limits, the Activate screen shows this message and the Activate button stays grey:

For example, with a basal rate of 0.10 U/h in the night and a profile percentage of 35 %, AAPS would have to deliver 0.035 U/h. This is less than a Dana pump can deliver (0.04 U/h).

To solve it, either:

• choose another percentage: a higher one if a basal rate becomes too low, a lower one if a basal rate becomes too high, or

• edit the profile and change the basal rate.

The profile editor only lets you start basal rates on a full hour. A basal rate starting at e.g. 06:30 can only come from an older profile, for example after you change to a pump that does not support it.

Insulin sensitivity factor (ISF)

Description

The insulin sensitivity factor (sometimes called correction factor) is a measure of how much your blood glucose level will be reduced by 1 unit of insulin.

In mg/dL units: If you have an ISF of 40, each unit of insulin will reduce your blood glucose by approx. 40 mg/dL (for example, your blood glucose will fall from 140 mg/dL to 100 mg/dL).

In mmol/L units: If you have an ISF of 1.5, each unit of insulin will reduce your blood glucose by approx. 1.5 mmol/L (for example from 8 mmol/L to 6.5 mmol/L).

From these examples you can see that the smaller the ISF value, the less sensitive you are to insulin. So if you reduce your ISF from 40 to 35 (mg/dL) or 1.5 to 1.3 (mmol/L), this is often called strengthening your ISF. Conversely, increasing the ISF value from 40 to 45 (mg/dL) or 1.5 to 1.8 (mmol/L) is weakening your ISF.

Impact

A lower / stronger ISF (e.g. 40 instead of 50) means insulin drops your BG less per unit. This leads to a more aggressive / stronger correction from the loop with more insulin. If your ISF is too strong (small value), this can lead to low BG.

A higher / weaker ISF (e.g. 45 instead of 35) means insulin drops your BG more per unit. This leads to a less aggressive / weaker correction from the loop with less insulin. If your ISF is too weak (large value), this can lead to high BG.

Example:

• BG is 190 mg/dL (10.5 mmol/L) and target is 100 mg/dL (5.6 mmol/L).

• So, you want a correction of 190 - 100 = 90 mg/dL or 10.5 - 5.6 = 4.9 mmol/L

• If ISF = 30 -> 90 / 30 = 3 or ISF = 1.63 -> 4.9 / 1.63 = 3: 3 units of insulin

• If ISF = 45 -> 90 / 45 = 2 or ISF = 2.45 -> 4.9 / 2.45 = 2: 2 units of insulin

An ISF that is too low (and therefore more aggressive, not uncommon) can result in ‘over corrections’, because AAPS calculates that the user needs more insulin to correct a high BG than actually required. This can lead to ‘roller coaster’ BG levels (esp. when fasting), as shown on the image below. In this circumstance, the ISF value should be increased in order to make AAPS less aggressive. This will ensure AAPS delivers smaller correction doses, and 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.

How to set it

See the figure below for an example of how ISF values could be set in an AAPS profile.

A basic starting point for determining your daytime ISF is to base it on your total daily dose (TDD) using the 1,700 (94) rule. More detail is given in Chapter 7 of “Think like a Pancreas” by Gary Scheiner.

1700 (if measuring in mg/dL) or 94 (mmol/L)/ TDD = approx ISF. Example: TDD = 40 U Approx ISF (mg/dL) = 1700/40 = 43 Approx ISF (mmol/L) = 94/40 = 2.4

Assuming your basal levels are correct, you can test this by suspending the 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.

Insulin to Carb ratio (ICR)

Description

The ICR is a measure of how many grams of carbohydrate are covered by one unit of insulin.

Some people also use I:C as an abbreviation instead of ICR, or talk about carb ratio : CR.

For example, a 1-to-10 (1:10) insulin-to-carb ratio means that you take 1U of insulin for every 10 grams of carbs eaten. A meal of 25g carbs would need 2.5U of insulin.

If your ICR is weaker (higher value), perhaps 1:20, you would only need 0.5U of insulin to cover 10 g of carbs. A meal of 25g of carbs would need 25/20 = 1.25U of insulin.

It is common to have different ICR at different times of day due to hormone levels and physical activity. Many people find they have their lowest/strongest ICR around breakfast time because they tend to be more insulin resistant. So, for example, one adult user’s ICR could be 1:8 for breakfast, 1:10 for lunch and 1:10 for dinner, but these patterns are not universal, and some people are more insulin resistant at dinner time, and require a stronger/smaller ICR then.

NOTE:

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 ICR 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?”)

Example:

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

Corresponding ICR: 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, e.g. here.

Impact

A lower / stronger ICR means less food per unit, i.e. you are getting more insulin for a fixed amount of carbs. Can also be called ‘more aggressive’. If your IC is too strong, you are getting too much insulin, this can lead to low BGs.

A higher / weaker ICR = more food per unit, i.e. you are getting less insulin for a fixed amount of carbs. Can also be called ‘less aggressive’. If your IC is too weak, you are getting less insulin than you need, this can lead to high BGs.

How to set it

The figure below shows an example of a user’s ICR and how it can be set in an AAPS Profile. When entering these values, we enter the final part of the ratio, so an insulin-to-carb ratio of 1:3.5 is entered simply as “3.5”.

If after a meal has been digested and the IOB has returned to zero, your BG remains higher than before food, chances are your ICR is too weak (i.e. the number is too high and should be gradually lowered). Conversely, if your BG is lower than before food, ICR is too strong (i.e. the number is too small and should be gradually increased).

Assuming your basal rates are correct, you can test by checking if 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 you normally eat at that time of day and count its carbs precisely.

Common questions related to the Profile

About the importance of getting your profile right

Why should I try to get my profile settings right? Can’t the loop just take care of it?

A hybrid closed loop can attempt to make insulin delivery adjustments to minimize poor glycemic control that results from having incorrect Profile values. It can do this, for example, by withholding insulin delivery if you are going to hypo. However, you can achieve much better glycemic control if your Profile settings are already as close as possible to what your body needs. This is one of the reasons that AAPS uses staged objectives to move from open loop pumping towards hybrid closed loop. In addition, there will be times when you need to open the loop (sensor warmups, sensor failure etc.), sometimes in the middle of the night, and you will want to have your settings right for these situations.

If you are starting with AAPS after using a different open or closed-loop pumping system, you will already have a reasonable idea of what values to use for basal rates (BR), insulin sensitivity factors (ISF) and insulin-to-carb ratios (ICR).

If you are moving from injections (MDI) to AAPS, then it is a good idea to read up on how to make the transfer from MDI to pump first, and plan and make the move carefully in consultation with your diabetes team. “Pumping insulin” by John Walsh & Ruth Roberts and “Think like a Pancreas” by Gary Scheiner are very useful.

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 reach 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 pre-bolus time with your endocrinologist.
If your BG is too high after the meal and still too high after carbs are fully absorbed, consider decreasing your ICR with your endocrinologist. If your BG is too high while COB and too low after carbs are fully absorbed, think about increasing your ICR and an appropriate pre-bolus time with your endocrinologist.

I’m stuck high and the loop does not bring me down

The possible reasons for AAPS not giving enough insulin are:

• ISF is not strong enough

• Basal rate might not be strong enough

• A security setting might kick in, such as maxIOB. Or SMB is disabled at this time, depending on your settings.

• Automation has been set up and has overridden AAPS.

See also Tweaking the AAPS Profile.

I have negative IOB, is this an issue ?

Negative IOB means the amount of absolute insulin (basal + bolus) in your body is less than the basal. It will cause AAPS to send more insulin as soon as the BG starts to rise, because it considers that insulin is missing, which can result in low BG later.

Here are some reasons why you may have negative IOB, and what action to take:

• a too strong basal: tweak your Profile

• too much bolus at the previous meal: tweak your Profile or check if you are bolusing at the right time.

• DIA set too short on your insulin type, resulting in insulin stacking: tweak it in Manage → Insulin settings

• physical activity: next time, consider using a lower Profile percentage during activity to account for increased sensitivity.

Manage your Profiles

Create and edit Profiles

In AAPS v4 your profiles live on the Manage screen (bottom navigation) → Profile, shown as a swipeable card carousel with an action bar (➕ Add, ✏️ Edit, ⧉ Clone, 🗑️ Delete, ▶ Activate). For managing and activating a profile, see Managing and activating profiles. Coming from AAPS v3, where profiles had their own tab? See What changed in AAPS v4.

Tapping ✏️ Edit opens the editor. Set the profile name and units, then fill in the four schedules using the tabs:

• IC — insulin-to-carb ratio (g/U)

• ISF — insulin sensitivity factor

• BAS — basal rates

• TARG — target range

Each schedule is a list of time blocks: add a block, set its start time and value, then Save.

If you make any changes to your Profile, make sure you are editing the correct Profile: the card of the profile in use is marked ACTIVE, but the card selected on screen may be another one.

Build a Profile from scratch for a kid

The Profile Helper (menu ☰ → Profile helper) may help you to create a profile for a child (up to 18 years).

Important note:

Profile helper is intended to support you finding the initial profile for your kid. Even though it is based on data sets of two different hospitals always discuss with your medical team before using a new profile!

Profile helper offers data sets from two different hospitals for children to find initial profile for your kid up to 18 years.

1. Make sure you are on the Profile 1 tab.

2. In Profile type, make sure you have “Default profile” selected.

3. Adjust Default profile (based on hospital data set) by entering kids age and either TDD Total or weight.

4. Change to the Profile 2 tab.

5. Press Profile type and select “DPV Default profile”.

6. Adjust DPV Default profile (based on another hospital data set) by entering kids age, TDD Total and percentage of basal. Note that the DPV data set provides basal rates only, so IC and ISF are shown as zero for this profile.

7. Open the Comparison tab. Comparison of the two adjusted profiles will be displayed (see screenshot below).

8. If you want to start tweaking your profile based on one of these suggestions, use the Clone button at the bottom of the comparison.

Switch Profile

See Profile switch & Profile Percentage.

Clone a Profile switch to a new Profile

The Treatments history shows all past Profile Switches. When going to the Profile switch tab, you can use a past Profile Switch as a base to create a new Profile. In this case, timeshift and percentage will be applied to the new local profile. Use the Clone button shown on line 2.

You can now go to the Profile screen (Manage → Profile) to edit the newly created Profile.

Profile backup

Being a core setting of your looping system, your Profiles are highly sensitive and something you really don’t want to lose.

• Your Profiles are stored in the AAPS database.

• When NSClientV3 is set up (see Synchronization), your Profiles are also uploaded to Nightscout automatically.

• They are also part of exported settings. So make sure to have a backup in a safe place.

Editing Profiles from Nightscout

If enabled, Profile changes made directly in Nightscout can be received in AAPS. The setting is called “Receive profile store from NS” and is part of the Nightscout data acceptance options (accepting data from Nightscout is turned off by default, see the Client control step of the Setup Wizard); you can find it quickly with the search bar on the main screen. While client control is on, the setting is hidden and AAPS takes no profile changes from Nightscout (hardened mode); edit the profile on a paired client instead, or load it once with Full sync.

This can be helpful when about to make major changes to a more extensive Profile. They can be entered more easily via the web interface, e.g. to manually copy data from a spreadsheet.

To do this, however, it is important to clone the whole database record consisting of several profiles in the Nightscout editor (blue arrow on the screenshot below). The new database records then carries the current date. After saving, the changed/new Profile can be activated in AAPS with a regular Profile switch.

Compare two Profiles

You can also use the Profile Helper (menu ☰ → Profile helper) to compare two different profiles or profile switches (percentage of one of your profiles used in a profile switch before).

1. Make sure you are on the Profile 1 tab.

2. In Profile type, select “Available profile” to choose between all stored Profiles.

3. Choose the Profile you want to compare from.

4. Change to the Profile 2 tab.

5. In Profile type, select “Profile switch” to choose in the history of all your Profile Switches.

6. Choose the Profile Switch you want to compare to.

7. Open the Comparison tab. Comparison of the two profiles will be displayed (see screenshot below).