Add more manual-style description for the DIA configuration#2607
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je-l
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Jul 12, 2026
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| This, together with the insulin type's peak time, results in the [insulin profile](#AapsScreens-insulin-profile), as shown in the image above. The important thing to note is that the decay has a **long tail**. If you have been used to manual pumping, you have probably been used to assuming that insulin decays over a much shorter period i.e. about 3.5 hours. However, when you are looping, the long tail matters as the calculations are far more precise and these small amounts add up when they are subjected to the recursive calculations in the **AAPS** algorithm. Therefore, **AAPS** uses a minimum of 5h as **DIA**. | ||
| In the above chart, in theory, half the IOB is decayed after ~110 minutes. The blue activity curve shows that at 120 minutes, IOB is decaying at a rate of 0.5 percentage points per minute. |
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I don't see the exact activity values in v4, in the new Insulin Manager... I hope developers could add them, I already pointed out this small flaw.
je-l
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Jul 12, 2026
| * [Revised Humalog model in a closed loop](https://bionicwookiee.com/2022/04/13/revised-humalog-model-in-a-closed-loop/) and other articles on Bionic Wookie, recommending a DIA of 9h for Lyumjev, Fiasp, NovoRapid, Humalog. | ||
| Recall that as AAPS applies TBR below profile basal rate, IOB is subtracted. Therefore, in the typical hybrid closed-loop AAPS use, positive IOB from meal bolus will in practice reach zero many hours earlier than the configured DIA. For the same reason, positive IOB from a small SMB will decay to zero very quickly after zero-temping. | ||
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| To configure DIA and peak, tap **Manage** in the main screen, and then tap **Insulin**. Due to the influence of TBR explained above and the mathematical formula used for IOB decay in AAPS, most users set a clearly higher DIA than in commercial systems. In general, many people find that a **DIA** of 9h works well for them. After you have more experience with AAPS and have a well-tuned profile, you can try to determine a personalized DIA and peak configuration with the information presented in the next section. |
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Giving a single, 9h suggestion for DIA. The old version had 6-7h, and then "growing number using 8-9h". I think this can add some confusion because people often recommend raising the DIA value from e.g. 6h to 9h, without realizing that this has quite different impact with Novorapid preset than Lyumjev preset. So I think we can prevent confusion by giving one, consistent "beginner default" here.
je-l
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Jul 12, 2026
| Please don't change the peak unless you are an expert — usually the preset values work well for each branded insulin. | ||
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| If you are a new AAPS user, set DIA to 9 hours. More details at [the DIA section of the docs](#Config-Builder-insulin-dia). |
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Currently many users might pick 5h DIA without understanding how DIA works, then they later read that generally higher values are recommended and raise the value. I think it makes sense to give consistent advice here and directly recommend the high 9h.
je-l
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Jul 12, 2026
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| The duration of insulin action is set to a single value per insulin type in **AAPS**, because your pump will continually infuse the same type of insulin. | ||
| AAPS models insulin action with a mathematical function, configured using **DIA** and the closely related **peak** settings. DIA represents a theoretical duration until IOB reaches zero and peak represents timepoint after insulin activity is strongest. Insulin activity and rate of IOB decay is one and the same. |
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"Insulin activity and rate of IOB decay is one and the same."
I'm 99% sure this is how it works, but highlighting this change just in case...
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#2594
This is now in pretty good shape, but I can refine further if needed.
In addition to the details how DIA works in AAPS, this also now directly suggests the 9h DIA for new AAPS users. I'll add couple inline PR comments.
Side note: Wow the quick progress already in updating the v4 screenshots!