Boost Plugin Tuning Guide

💉

Core Delivery Controls

Primary levers for how much insulin Boost delivers

Boost Scale ApsBoostScale

Direct multiplier on calculated Boost insulin. Values ≥ 3.0 disable Boost entirely and fall back to oref1.

1.0

0.1 (min)3.0 disables Boost

Max IOB ApsBoostMaxIob

IOB ceiling. Above this, Boost falls back to standard oref1. Acts as a hard safety limit.

1.0 U

0.1 U12.0 U

Bolus Cap ApsBoostBolus

Maximum insulin per individual Boost SMB delivery regardless of other calculations.

2.5 U

0.1 U10.0 U

Insulin Required % ApsBoostInsulinReqPct

What fraction of the algorithm's calculated insulin need to actually deliver as an SMB.

50%

30% (cautious)100% (full)

Percent Scale Factor ApsBoostPercentScale

Max scale factor when BG is 108–180 mg/dL with rising delta. Only active if Percent Scaling is enabled.

200%

50%500%

📐

Dynamic ISF

How insulin sensitivity is calculated from TDD and BG

BG Impact on ISF ApsBoostDynIsfVelocity

How much current BG level shifts ISF. 0% = constant ISF from TDD only. 100% = ISF scales fully with BG level. V2: always 100%.

100%

0% (flat)100% (BG-reactive)

DynISF Normal Target ApsBoostDynIsfNormalTarget

Reference BG used in the ISF formula. Lower = more aggressive ISF at a given BG.

99 mg/dL

70 (aggressive)120 (conservative)

DynISF BG Cap ApsBoostDynIsfBgCap

BG above this is softened: effective BG = cap + (actual − cap) ÷ 3. Prevents extreme ISF at very high BG.

210 mg/dL

100 (more softening)300 (less softening)

TDD Adjustment Factor ApsBoostDynIsfAdjustmentFactor

Scales the TDD used in ISF calculation. Below 100% = treats you as lower TDD = weaker ISF = less insulin.

100%

1% (very weak ISF)300% (very strong ISF)

BOOST v1 ISF Formula

ISF = 1800 ÷ (TDD × ln(target ÷ div + 1))

TDD is a blended 8h/7D/1D weighted average. Velocity scales BG sensitivity.

BOOST v2 ISF Formula (Chris Wilson)

ISF = 2300 ÷ (ln(target ÷ div + 1) × TDD² × 0.02)

Squares TDD — more sensitive to TDD changes. Velocity is always 1.0.

🏃

Activity Detection

Step-count thresholds and insulin adjustment when active

When ANY threshold below is exceeded, the Activity Profile % is applied and BG target is set to 150 mg/dL (if no temp target is active).

5-min window

420

steps triggers active

30-min window

1,200

steps triggers active

60-min window

1,800

steps triggers active

Activity Profile % ApsBoostActivityPct

Applied when active. <100% = more insulin (treats activity as insulin-requiring). >100% = less insulin.

80%

30% (more insulin)150% (less insulin)

Inactivity Profile % ApsBoostInactivityPct

Applied when steps/hr is below inactivity threshold. >100% = less insulin during sedentary periods.

130%

100% (no change)200% (much less insulin)

Inactivity Threshold ApsBoostInactivitySteps

Steps per hour below which inactivity mode triggers. Higher = easier to trigger inactivity reduction.

500/hr

1 steps/hr1,000 steps/hr

🌙

Night Mode & Sleep-in

SMB suppression near target during sleep hours

Night Mode

Disables SMBs during night window when BG is near target (within BG Offset)

Default: OFF

Night Mode BG Offset ApsBoostNightModeBgOffset

SMBs suppressed when BG < (profile target + offset). Higher offset = more aggressive suppression zone.

27 mg/dL

0 (only at target)90 mg/dL (wide zone)

Disable Night Mode if COB > 0

Allow SMBs during night if carbs on board

Default: OFF

Disable Night Mode with Low TT

Allow SMBs if a low temp target is active during night window

Default: OFF

Sleep-in Detection

Sleep-in Hours ApsBoostSleepInHours

Window after Boost start time where sleep-in is detected. If still inactive during this window, inactivity mode continues.

2 hrs

0 hrs (disabled)18 hrs

Sleep-in Step Threshold ApsBoostSleepInSteps

Steps/hr below which sleep-in is confirmed within the window. Higher = easier to trigger.

250/hr

1 steps/hr1,000 steps/hr

⚙️

Feature Toggles

Enable/disable major Boost features

TDD-based ISF

Calculates ISF from Total Daily Dose. Required for Boost's dynamic ISF to function. Mandatory for V2.

Default: OFF

TDD Sensitivity Adjustment

Adjusts sensitivity using 24h vs 7D TDD ratio (like Autosens). Start with OFF.

Default: OFF

Boost Percentage Scaling

Scales SMBs when BG is 108–180 mg/dL with rising delta. Uses Percent Scale Factor.

Default: OFF

Circadian ISF

Applies time-of-day multiplier to ISF based on circadian polynomial model. Low overnight, peaks afternoon.

Default: OFF

High TT Raises Sensitivity

When exercise temp target is active, increase ISF (reduce insulin delivery).

Default: OFF

Low TT Lowers Sensitivity

When correction temp target is active, decrease ISF (increase insulin delivery).

Default: OFF

Allow Boost with High Temp Target

By default, Boost is disabled when a high temp target is set. Enable to override this.

Default: OFF

⏰

Time Window & Safety

When Boost is active and data source safety checks

Boost only runs within its configured time window. Outside the window, oref1 standard behaviour applies. The default window (07:00–07:01) is effectively disabled — you must set a real window.

Boost Start Time ApsBoostStartTime

Time Boost becomes active each day (24h HH:mm format).

        Default: 07:00 → Set to your wake-up time
      

Boost End Time ApsBoostEndTime

Time Boost deactivates. Can span midnight (end < start).

        Default: 07:01 → Set to your end-of-day / bedtime
      

Safety Settings

Allow All BG Sources

Bypasses advanced CGM filtering. Only use with reliable, validated CGM data.

Default: OFF

Bypass Version Expiry Check

Prevents AAPS disabling closed loop on version expiry. You accept responsibility for running old code.

Default: OFF

⚠️ Safety settings should remain OFF unless you fully understand the implications. They exist for edge cases, not routine use.

🎯

Quick Reference: Tuning Direction

Starting points when you need more or less aggressiveness

To make Boost more conservative

Lower Boost Scale (e.g. 0.7–0.8)
Lower Max IOB to limit how long Boost stays active
Lower Bolus Cap to reduce per-SMB size
Lower Insulin Required % (e.g. 30–40%)
Lower DynISF Velocity to reduce BG reactivity
Raise DynISF Normal Target (less aggressive ISF reference)
Enable Night Mode with a larger BG Offset
Raise Inactivity Profile % (more suppression when sedentary)
Enable High TT Raises Sensitivity

To make Boost more aggressive

Raise Boost Scale (e.g. 1.2–2.0, not ≥3)
Raise Max IOB to allow more sustained Boost delivery
Raise Bolus Cap to allow larger SMBs
Raise Insulin Required % toward 100%
Raise DynISF Velocity to 100% (full BG reactivity)
Lower DynISF Normal Target (stronger ISF reference)
Enable Percent Scaling for rising-BG amplification
Enable Low TT Lowers Sensitivity for correction targets
Raise TDD Adjustment Factor above 100%

Boost V2 differences to keep in mind: V2 uses TDD² in its ISF formula — it is more sensitive to TDD changes than V1 and reacts more strongly to short-term variations. BG Velocity is always 100% in V2 and cannot be reduced. Start with conservative delivery settings (lower Scale, lower Max IOB) when switching to V2.

What is likely happening

Boost's COB tiers (Tier 1 <25 min, Tier 2 <40 min) deliver insulin proportional to insulinReq, which is driven by current ISF and the gap between BG and target. If ISF is tuned aggressively or insulinReqPct is high, these tiers stack significant insulin on top of the meal bolus.

If the profile ISF is too low (number too small), the algorithm overestimates how much insulin is needed per mg/dL correction. Combined with a large Max IOB headroom, this allows continued stacking well into absorption.

Boost's Fast Carb Protection reduces aggressiveness when a recent low + fast rise is detected, but it cannot fire if the hypo itself is triggered by the overcorrection — the protection is for pre-emptive fast carb scenarios, not post-delivery correction.

Settings to change

Insulin Required % first
Reduce to 35–40%. This directly scales how much of the calculated need is acted on during COB tiers.
ApsBoostInsulinReqPct → 35–40%
Max IOB first
Lower to 0.5–0.8 U. When IOB exceeds this, Boost falls back to oref1 — this prevents stacking beyond a safe ceiling.
ApsBoostMaxIob → 0.5–0.8 U
Bolus Cap
Reduce to 1.0–1.5 U as a hard ceiling on any single SMB delivery.
ApsBoostBolus → 1.0–1.5 U
Boost Scale
If hypos persist after the above, reduce scale to 0.7–0.8. This reduces the Tier 3+ UAM bolus magnitude.
ApsBoostScale → 0.7–0.8
Profile ISF (outside Boost settings)
Verify ISF is not too low (too aggressive). A too-low ISF means insulinReq is overestimated at every step. Fasting basal testing first, then ISF.
Profile CR (outside Boost settings)
A too-low CR (too aggressive) means the pre-meal bolus already overdoses before Boost fires. Check CR separately from Boost.

What not to do

Don't set Scale ≥ 3.0 to disable Boost as your first response — you lose all Boost benefit and revert to standard oref1 which may have worse meal coverage.
Don't raise the DynISF Normal Target as a first fix — this makes ISF less aggressive at a given BG but doesn't address the stacking behaviour during COB tiers.
Don't extend Night Mode hours into the day to suppress post-meal SMBs — this is a blunt instrument that will block needed corrections at other times.
Don't reduce smbBasalMinutes in isolation — this only limits per-SMB size; if ISF is wrong, the algorithm will just deliver more frequent small SMBs instead.
Don't ignore profile calibration — Boost amplifies what the profile tells it. A miscalibrated ISF or CR will always produce bad meal outcomes regardless of Boost settings.

What is likely happening

The algorithm is calculating an insulinReq but delivering only a fraction of it — either because insulinReqPct is low, or because Max IOB is hit quickly and Boost falls back to oref1 which delivers standard corrections.

During a post-meal plateau where BG is stable but high (flat delta), Boost uses Tier 7 (mild correction) or standard oref1 logic rather than the more aggressive UAM tiers, because acceleration signals are gone. The correction speed is then entirely governed by ISF and Max IOB headroom.

If Percent Scaling is disabled, the rising 108–180 mg/dL window never gets the amplified SMB it's designed to handle. Enabling this is specifically designed for this pattern.

A too-high ISF (conservative number) underestimates insulinReq — each SMB chips away slowly. Verify ISF is accurate for corrections.

Settings to change

Verify Boost time window first
Confirm the window covers your meal times. The default (07:00–07:01) is essentially disabled. If Boost isn't active, you're on standard oref1 only.
ApsBoostStartTime / ApsBoostEndTime
Max IOB first
Raise to 2.0–3.0 U. A low Max IOB ceiling is the most common reason Boost stops correcting early — check the loop graph for IOB hitting the ceiling.
ApsBoostMaxIob → 2.0–3.0 U
Enable Percent Scaling
Specifically designed for BG in the 108–180 rising range. Set Percent Scale Factor to 200–300% to amplify SMBs as BG rises through this band.
ApsBoostEnablePercentScale → ON

ApsBoostPercentScale → 200–300%
Insulin Required %
Raise to 70–80%. Delivers more of the calculated need per loop cycle rather than a conservative fraction.
ApsBoostInsulinReqPct → 70–80%
maxSMBBasalMinutes
Raise to 60 min. This increases the per-SMB ceiling, allowing larger individual corrections when insulinReq warrants it.
maxSMBBasalMinutes → 60 min
DynISF Normal Target
Lower from 99 to 90 mg/dL. This makes the ISF formula produce a stronger (lower) ISF value, increasing insulinReq for a given BG gap.
ApsBoostDynIsfNormalTarget → 90 mg/dL

What not to do

Don't raise Boost Scale above 2.0 before verifying Max IOB and Insulin Required % are correct — scale amplifies Tier 3+ UAM boluses but has little effect on plateau corrections where acceleration is flat.
Don't rely on Scale alone for plateaus — scale primarily affects the fast-rise UAM tiers. Once BG is flat and high, the plateau is corrected by ISF and IOB headroom, not scale.
Don't raise TDD Adjustment Factor aggressively (e.g. 200%+) to force stronger ISF — this distorts the Dynamic ISF calculation away from your actual insulin needs and can create instability.
Don't ignore Boost time window — it's the most common reason Boost appears not to be working. Verify in the AAPS loop view that the plugin shows "BOOST ACTIVE".
Don't tighten CR to compensate for post-meal plateaus — if Boost is active and adequately configured, a tight CR risks pre-meal overdose. Correct the loop behaviour first.

What is likely happening

Persistent above-target BG between meals usually signals a profile calibration problem rather than a Boost tuning problem. The algorithm can only correct what the profile's ISF and basal allow it to correct.

If TDD-based ISF is disabled, Boost uses the profile ISF directly. If that ISF is too conservative (too high a number), every correction is undersized. Dynamic ISF's purpose is to adapt — without it, the algorithm is no better than standard oref1.

Night Mode or inactivity suppression may be blocking corrections during parts of the day where BG is chronically high. If these features fire during waking hours, they prevent SMBs when they're most needed.

A too-low Max IOB hits the ceiling quickly during sustained correction periods. Autosens will attempt to compensate but is bounded by its min/max ratio limits.

Settings to change

Enable TDD-based ISF first
If not already on, this is the most impactful change. Boost's Dynamic ISF is the core mechanism for adapting corrections to your actual insulin needs.
ApsBoostUseTdd → ON
Verify Boost time window first
Confirm Boost is active during the problem periods. Check the AAPS loop graph — the plugin label should show "BOOST" not "SMB".
ApsBoostStartTime / ApsBoostEndTime
Max IOB
Raise to 2.0–3.0 U. Persistent highs often mean the algorithm is trying to correct but hitting the IOB ceiling and backing off. Check the loop graph for this pattern.
ApsBoostMaxIob → 2.0–3.0 U
DynISF Normal Target
Lower from 99 to 90–95 mg/dL to make the ISF formula produce stronger corrections at elevated BG.
ApsBoostDynIsfNormalTarget → 90–95 mg/dL
Review Night Mode & Inactivity settings
Confirm Night Mode hours do not overlap with when you are awake and high. Check that inactivity % is not suppressing insulin during sedentary work hours when BG is elevated.
ApsBoostNightModeStart / End — check overlap

ApsBoostInactivityPct → reduce if needed
Enable Low TT Lowers Sensitivity
When you deliberately set a correction temp target, this makes the algorithm more aggressive. Useful for managing persistent highs intentionally.
ApsAutoIsfLowTtLowersSens → ON
Profile basal and ISF (outside Boost settings)
Persistent above-target BG is often a signal that the profile basal or ISF is fundamentally too conservative. Autosens will show a persistent ratio > 1.0 if it's trying to compensate. Address the root cause in the profile.

What not to do

Don't raise TDD Adjustment Factor above 150% as a workaround for poor profile calibration — this forces the ISF formula to behave as if you use far more insulin than you do, creating instability and potential hypo risk when your real TDD is used.
Don't raise Boost Scale to near 3.0 — high scale inflates UAM bolus tiers but has minimal effect on persistent between-meal highs where BG is flat. It also increases hypo risk when you eventually come back on target.
Don't ignore autosens ratio — if autosens is sitting persistently at its maximum (e.g. 1.2), it's hitting its ceiling trying to compensate for a miscalibrated profile. Widening autosens limits is not the fix; correcting the profile is.
Don't set a high BG target in the profile to "avoid lows" — if the profile target is 130+ mg/dL, the algorithm will never drive BG below that regardless of settings. Set a correct target and use night mode for overnight protection instead.
Don't increase Bolus Cap to try to force larger corrections — between-meal corrections are limited by insulinReq (ISF × BG gap), not bolus cap. Bolus cap only limits the ceiling; if insulinReq is already below the cap, raising the cap does nothing.

Boost Plugin Tuning Guide

To make Boost more conservative

To make Boost more aggressive

Common Scenario Guides