Personal Best Establishment
Two good-control weeks set the number every zone depends on.
- 2 weeks: Measurement window (twice-daily readings)
- 3: Readings per session (best of three kept)
- Highest: Best value used (not the average)
- Annually: Re-check interval (or after major flare)
What personal best means
Your highest peak flow during stable, symptom-free weeks.
Predicted norms mislead — always zone against your own best.
How the baseline gets measured
Blow into the meter three times, keep the highest score.
Why timing matters
Measure during two weeks of good asthma control.
Green Zone — Doing Well
Eighty to one hundred percent of best means stay the course.
- 80–100%: Zone range (of personal best)
- None: Action needed (continue usual plan)
- Minimal: Symptom presence (no wheeze or cough)
- Daily: Check frequency (morning readings)
What green signals
Airways are open and controller medication is working.
Green still means keep logging — trends can turn quickly.
Daily routine in green
Take controller medicine as prescribed, keep logging each morning.
Watching for change
A single low reading is not yet a warning sign.
Yellow Zone — Caution
Fifty to seventy-nine percent signals airways are narrowing.
- 50–79%: Zone range (of personal best)
- Step up: Action needed (reliever or controller)
- 1 hour: Recheck window (after reliever use)
- Mild: Typical symptoms (cough, tight chest)
What yellow signals
Airways are narrowing before symptoms feel severe.
Yellow is the window to prevent an emergency, not ignore it.
Recommended response
Use a reliever inhaler and follow the written action plan.
When to escalate
If readings stay yellow after treatment, call your clinician.
Red Zone — Medical Alert
Below fifty percent means seek emergency care immediately.
- <50%: Zone range (of personal best)
- Emergency: Action needed (call for help now)
- Minutes: Response time (not hours)
- Severe: Risk level (possible respiratory failure)
What red signals
Severe airflow obstruction — a medical emergency is underway.
Red zone with no relief after reliever use means call emergency services.
Immediate steps
Take rescue medication and seek emergency care right away.
After the emergency
Review the action plan with a clinician before returning home.
Daily Trend Tracking
A quiet decline often precedes symptoms by several days.
- 3+ days: Warning pattern (consecutive decline)
- 2–5 days: Lead time gained (before symptoms flare)
- Morning: Best logging time (before medication)
- Diary/app: Log format (shared with clinician)
Why trends matter more than one reading
A single dip is noise, a run of dips is signal.
Gradual decline over days can precede visible symptoms entirely.
Reading the log
Consecutive falling mornings justify calling before symptoms appear.
Turning data into action
Share the trend log at every asthma review visit.