diff --git a/apps/hrmmar/README.md b/apps/hrmmar/README.md
index 2d9612117..4f512c773 100644
--- a/apps/hrmmar/README.md
+++ b/apps/hrmmar/README.md
@@ -2,6 +2,8 @@
 
 Measurements from the build in PPG-Sensor (Photoplethysmograph) is sensitive to motion and can be corrupted with Motion Artifacts (MA). This module allows to remove these.
 
+**WARNING:** On Bangle.js 2 this has been found to make heart rate readings [substantially less accurate in some cases](https://github.com/orgs/espruino/discussions/7738#discussioncomment-13594093) (the HRM already has built in motion artefact removal).
+
 ## Settings
 
 * **MA removal**
diff --git a/apps/hrmmar/metadata.json b/apps/hrmmar/metadata.json
index fcb2fac5c..5ff49f3fc 100644
--- a/apps/hrmmar/metadata.json
+++ b/apps/hrmmar/metadata.json
@@ -4,7 +4,7 @@
   "shortName":"HRM MA removal",
   "icon": "app.png",
   "version":"0.02",
-  "description": "Removes Motion Artifacts in Bangle.js's heart rate sensor data.",
+  "description": "Removes Motion Artifacts in Bangle.js's heart rate sensor data. **WARNING:** On Bangle.js 2 this has been found to make heart rate readings substantially less accurate in some cases.",
   "type": "bootloader",
   "tags": "health",
   "supports": ["BANGLEJS","BANGLEJS2"],