Blood-pressure cuff
Technique, cuff size, position and timing affect readings. A validated upper-arm device and repeated protocol-labelled readings are more useful than a single number.
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reference library
Device data literacy
Separate what a consumer device estimates from what it cannot conclude, then choose whether to keep, simplify, discuss or stop tracking.
Use it thoughtfully
Scale or body composition
Weight varies and impedance estimates change with hydration and conditions. Neither directly measures fitness, function or individual future health.
Watch or ring
Heart rate, sleep and recovery metrics are estimates with device- and context-dependent error. Consumer sleep stages are not a clinical sleep study.
Continuous glucose monitor
Sensor glucose can lag blood glucose and readings vary by device and context. In people without a clinical indication, more data does not automatically improve outcomes.
Your worksheet
A keep, simplify, discuss or stop decision for each device or metric.
Boundaries and sources
This tool does not
- No medical interpretation, merged score, food judgement or product recommendation.
- Diabetes-technology evidence is not presented as evidence of benefit in adults without diabetes.
Evidence links
Content owner: Healthspan content and clinical governance · Reviewed: 2026-07-13 · Next review due: 2027-07-13
- Accuracy and acceptability of wrist-wearable activity-tracking devices: systematic reviewJournal of Medical Internet Research · reviewed 2026-07-13
- Accuracy of Fitbit Charge 4, Garmin Vivosmart 4, and WHOOP versus polysomnography: systematic reviewJMIR mHealth and uHealth · reviewed 2026-07-13
- Measuring your blood pressureUS Centers for Disease Control and Prevention · reviewed 2026-07-13
- Diabetes technology: Standards of Care in Diabetes—2026American Diabetes Association Professional Practice Committee · reviewed 2026-07-13
- General wellness: policy for low risk devicesUS Food and Drug Administration · reviewed 2026-07-13