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# Dynamic ISF (DynISF)
Up until now, with **AMA** and **SMB**, **ISF** was defined in the **Profile** and was static for each defined period in the day. But in reality, a person’s **ISF** is not that static and varies depending on their **BG** level: when at a high BG level, the user will need more insulin to bring their **BG** down 50mg/dL / 3mmol/L than compared to a lower **BG**. [Autosens](#Open-APS-features-autosens) was the first algorithm to try and address this issue, by adjusting **ISF** outside of mealtimes.
**Dynamic ISF** (also called **DynISF**) serves the same purpose but is more advanced as it can be used at all times. It is recommended only for advanced users that have a good handle on their **AAPS**’ controls and monitoring. Read the [Things to consider when activating Dynamic ISF](#dyn-isf-things-to-consider-when-activating-dynamicisf) below before trying it out.
```{admonition} CAUTION - Automations or Profile Percentage change
:class: warning
**Automations** should always be used with care. This is particularly so with **Dynamic ISF**.
When using **Dynamic ISF**, disable any temporary **Profile** change as an **Automation** rule, because it would cause **Dynamic ISF** to be overly aggressive in correction bolusing and result in hypoglycemia. This is the exact purpose of **Dynamic ISF** and so there is no need for **AAPS** to be told to provide additional insulin by way of Automation in the event of high **BGs**.
```
To use **Dynamic ISF**, **AAPS'** database requires a minimum of 7 days of the user's **AAPS** data.
## What does Dynamic ISF do ?
**Dynamic ISF** adapts the insulin sensitivity factor (**ISF**) dynamically based on the user's:
- 每日胰岛素总剂量（TDD）；
- 当前和预测的血糖值。
When using **Dynamic ISF**, the **ISF** values entered in the **Profile** are not used at all anymore, except as a fallback if there is not enough TDD data in **AAPS** database (*i.e.* fresh reinstallation of the app).
**SMB/AMA** - an example of a user's **Profile** with static **ISF** as set by the user and utilised by **SMB** and **AMA**.
**Dynamic ISF** - an example of a user's **ISF** subject to change as determined by **Dynamic ISF**.
The section circled in red shows: `profile ISF` -> `ISF as calculated by DynISF`.
Taping on this section shows a dialog with additional information, such as the **ISF** used for the calculator and carbs absorption (see [Other usages of ISF](#dynisf-other-usages-of-isf) below).
The **DynISF** value can also be shown in an additional graph, enabling “Variable sensitivity” data. It shows as a white line (see red arrow on the image above).
## How is Dynamic ISF calculated ?
**Dynamic ISF** uses Chris Wilson’s model to determine **ISF** instead of the user's static **ISF** value as set within the **Profile**. A detailed explanation can be found here: [Chris Wilson on Insulin Sensitivity (Correction Factor) with Loop and Learn, 2/6/2022](https://www.youtube.com/watch?v=oL49FhOts3c).
The **Dynamic ISF** equation implemented is: `ISF = 1800 / ((TDD * DynISF Adjust Factor) * Ln (( current BG / insulin divisor) + 1 ))`
The variables used in this equation are detailed below.
Note : `Ln` stands for natural logarithm, a mathematical function.
The implementation uses the above equation to calculate current **ISF** and in the oref1 [predictions for **IOB**, **ZT** (zero-temping) and **UAM**](#aaps-screens-prediction-lines). It is also used for **COB** and in the bolus wizard (see [Other usages of ISF](#dynisf-other-usages-of-isf) below).
### 总日剂量（TDD）
TDD将使用以下值的组合：
1. 7 day's average **TDD**;
2. 前一天的**TDD**；
3. 过去八小时胰岛素使用量的加权平均值，并推算出24小时的值。
The **TDD** used in the above equation is weighted one third of each of the above values.
### 动态ISF调整因子
This is set within the user’s **Preferences** and is used to make **Dynamic ISF** more or less aggressive. See the [Preferences](#dyn-isf-preferences) section below.
### 胰岛素除数
胰岛素除数取决于所使用的胰岛素的峰值，并且与峰值时间成反比。 对于Lyumjev，此值为75；对于Fiasp，为65；对于常规速效胰岛素，为55。
### ISF based on predicted BG for dosing decisions
Dynamic sensitivity is computed with the **current BG** value, and displayed as your current ISF in **AAPS**. But when doing dosing calculations, the oref1 algorithm computes and uses **Future ISF** instead.
This is done to prevent dosing too much insulin when **BG** is low or predicted to go low.
**Future ISF** uses the same formula as described above, except that it may use **minimum predicted BG** instead of **current BG**. **Minimum predicted BG**, [as calculated in oref1](https://openaps.readthedocs.io/en/latest/docs/While%20You%20Wait%20For%20Gear/Understand-determine-basal.html), is the minimum value your BG is predicted to go during all the course of the predictions.
* If the current **BG** is above target
**and** if **BG** levels are flat, within +/- 3 mg/dL:
BG is used in the formula as follows: `average(minimum predicted BG, current BG)`.
* If eventual **BG** is above target and glucose levels are increasing,
**or** eventual **BG** is above current **BG**:
BG is used in the formula as follows: `current BG`.
* Otherwise:
BG is used in the formula as follows: `minimum predicted BG`.
For a simplified explanation, refer to the screenshot below, which illustrates the above situation. Orange dots use **predicted BG**, purple dots use **average(predicted BG, current BG)**, and blue dots use **current BG**.
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## Other usages of ISF
### ISF and COB absorption
As described in the [COB Calculation](../DailyLifeWithAaps/CobCalculation.md) page, usually, the absorption of COB is calculated with this formula :
`absorbed_carbs = deviation * ic / isf`
When using **Dynamic ISF**, the **ISF** used here is the average of past 24h Dynamic ISF values.
### ISF in Bolus Wizard
When using the [Bolus wizard](#aaps-screens-bolus-wizard), **ISF** is used if **BG** is above target to add a correction.
When using **Dynamic ISF**, the **ISF** used here is the average of past 24h Dynamic ISF values.
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## Preferences
Check **Enable dynamic sensitivity** in [Preferences > OpenAPS SMB](#Preferences-openaps-smb-settings) to activate. New settings become available once selected.
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### 动态ISF调整因子
**Dynamic ISF** works based on a single rule which is supposed to apply to everyone, implying that people having the same **TDD** would have the same sensitivity. As each user has their own personal sensitivity, the **Adjustment Factor** allows the user to define whether they are more or less sensitive to insulin than the "standard" person.
The **Adjustment Factor** is a value between 1% and 300%. This acts as a multiplier on the **TDD** value.
* Increasing this value above 100 % makes **DynISF** more aggressive: the **ISF** values become *smaller* (_i.e._ more insulin required to decrease **BG** levels a small amount)
* Lowering this value under 100% makes **DynISF** less aggressive: the **ISF** values become larger (_i.e._ less insulin required to decrease **BG** levels a small amount).
The **Adjustment Factor** is also altered when activating a [**Profile Switch** with percentage](../DailyLifeWithAaps/ProfileSwitch-ProfilePercentage.md). A lower **Profile Percentage** will lower the **Adjustment Factor**, and vice versa in respect of higher **Profile Percentage**.
For example, if your **Adjustment Factor** is 80%, and **Profile Switch** to 80% is actioned , the resulting **Adjustment Factor** will be `0.8*0.8=0.64`.
This means that, when using **DynISF**, you can use **Profile Percentage** to temporarily fine tune your sensitivity manually. This can be useful for physical activity (lower percentage), illness (higher percentage), etc.
### BG level below which low glucose suspend occurs
**BG** value below which insulin is suspended. Default value uses the standard target model. A user can set this value between 60mg/dl (3.3mmol/l) and 100mg/dl(5.5mmol/l). Values below 65/3.6 result in use of the default model.
### 启用基于TDD的敏感性比率以调整基础率和血糖目标
此设置替换了Autosens，并使用过去24小时**TDD**与7天**TDD**的比率作为基础来增加或减少基础率，这与标准Autosens的方式相同。 如果启用了根据敏感性调整目标的选项，则此计算值也用于调整目标。 与Autosens不同，此选项不会调整**ISF**值。
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## Things to consider when activating Dynamic ISF
* 该功能仅推荐给那些已经熟练掌握**AAPS**控制和监测的高级用户。 Users should ideally have attained good control with **SMB** before moving onto **Dynamic ISF**.
* As mentioned above, turn off all [**Automations**](../DailyLifeWithAaps/Automations.md) which activate a **Profile Percentage** in relation to **BG** because it will be too aggressive and may over deliver in insulin! This is already part of the **Dynamic ISF** algorithm.
* [Profile Percentage](../DailyLifeWithAaps/ProfileSwitch-ProfilePercentage.md) is taken into account for the Dynamic ISF calculation (see [Dynamic ISF Adjustment Factor](#dyn-isf-adjustment-factor) above). It is bad practice to use a **Profile Percentage** other than 100% for a long time. If you determine that your **Profile** has changed, create a new **Profile** with your revised values in order to replicate the **Profile** with a specific percentage.
* **Dynamic ISF** may not work for everyone. Specifically, you may see unexpected results if one of these situations apply to you:
* Variable lifestyle (inconsistent eating or physical activity patterns)
* Inconsistent TDD or sensitivity from day to day.
* There is no precise guide to set the initial value of the **Adjustment Factor**. However, as a starting point: assuming your **Profile** values are correct, when you are in range and **BG** levels are flat, the **DynISF** value should be about the same as the one you had in your **Profile** before.
If you see that **Dynamic ISF** is too aggressive, lower the **Adjustment Factor**, and vice-versa.
* Even though **DynISF** does not use **Profile ISF** at all, if you notice that your sensitivity is very different from what was previously stored in your **Profile**, you should consider keeping it up-to-date. This may be useful in case you loose your **AAPS** data (_i.e._ new phone, new **AAPS** version…), as your **Profile ISF** will be used as fallback for the next 7 days.