Peak Flow Log: Asthma Diary

Zones, reliever log & PDF

Only for iPhone

Free · In‑App Purchases · Designed for iPhone. Not verified for macOS.

iPhone

Log your peak flow in seconds and instantly see your green, yellow or red zone from your personal best. Offline, private, one-time purchase. Peak Flow Log turns your daily peak-flow reading into a clear picture you and your doctor can act on. Blow into your own peak-flow meter, type in the number, and the app instantly shows your zone as a percentage of your personal best: - GREEN, YELLOW or RED at a glance, based on your own numbers - Log reliever (rescue) inhaler puffs, symptoms and triggers in one tap - See your trend over time with clear color-coded zone bands - Track more than one person, so parents can follow their child too - Create a clean PDF report to share at every appointment Built to be trustworthy: - Works fully offline. No account, no sign-in. - Your data stays on your device. Nothing is uploaded. - Export and import a backup so you never lose your history when changing phones. - One-time purchase to unlock Pro. No subscription. Free to log and see your zones. Pro unlocks the doctor PDF, unlimited profiles, full 90-day and all-time trends, and custom zone thresholds. Peak Flow Log records and visualizes readings you take with your own meter. It does not diagnose, treat, or provide medical advice, and it is not a medical device. Zones are based on a percentage of your personal best that you or your clinician set. Always follow the asthma action plan given by your doctor, and seek medical help in an emergency.

  • 3.0
    out of 5
    1 Ratings

Thank you for your feedback — this update fixes the problems you reported. • Fixed: Pro couldn't be purchased in some countries, including the US. It can now be bought everywhere the app is available. • New for Pro: Trigger & reliever insights in History — your most common triggers with the average % of personal best on those readings, and reliever use by time of day. • Buying Pro is more reliable: the App Store product is retried if it doesn't load the first time, and the message now explains what to do. • Your history is safer: a single damaged entry can no longer hide your other readings, and an unreadable data file is kept aside instead of being overwritten. • Deleting a reading now asks for confirmation. • Changing the Green zone cutoff no longer resets your custom Yellow cutoff to the default. • Japanese: messages and alerts are now translated.

The developer, Yoshifumi Sato, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .

  • Data Not Collected

    The developer does not collect any data from this app.

    Privacy practices may vary, for example, based on the features you use or your age. Learn More

    The developer has not yet indicated which accessibility features this app supports. Learn More

    Seller
    • Yoshifumi Sato
    Size
    • 2.1 MB
    Category
    • Health & Fitness
    Compatibility
    Requires iOS 17.0 or later.
    • iPhone
      Requires iOS 17.0 or later.
    • Mac
      Requires macOS 14.0 or later and a Mac with Apple M1 chip or later.
    • Apple Vision
      Requires visionOS 1.0 or later.
    Languages
    • English and Japanese
    Age Rating
    4+
    In-App Purchases
    Yes
    Copyright
    • © 2026 Peak Flow Log