Koharu
An air pressure and symptom diary for people who see a doctor regularly
An iPhone app for people who see a doctor for migraine, weather-related headaches, dizziness, fatigue or other long-term symptoms. It keeps changes in air pressure, your medications and how each day went in a form you can show your doctor.
What Koharu does
- Air pressure, hour by hourKoharu checks air pressure for your current location (or, in Japan, a prefecture) every hour from Apple Weather. Home shows the past and next 24 hours and the 24-hour change next to today's severity. Days when pressure drops by 6 hPa (0.18 inHg) or more in 24 hours are marked in the monthly log.
- Prescriptions from an Okusuri Techo QR codeJapanese pharmacies print a QR code (in the electronic medication handbook format) on the receipt and the medication handbook (Okusuri Techo) sticker. Koharu reads it with the camera or from a photo, compares it with the medications you have added and shows what is new, missing from the prescription or changed in dose. Only the changes you confirm are recorded, dated on the dispensing day.
- A monthly log for appointmentsFor each day: morning, afternoon and night severity (− + ++ +++), as-needed medications and how many, period, pressure drops, flare days and notes. It fills in from what you tell Koharu, and you can edit it by hand. It also counts the days with as-needed medication and headache days in the month. You can view it for free in the Records tab.
From daily logs to your appointment
Log by talking
Type or say "my temples have been throbbing since this morning," and Koharu replies while turning the symptom, severity, time of day, how it feels, triggers and medications into a log card. Replies and log cards are written by AI, and you can edit the log card later. Speech is turned into text on your iPhone. You can also log by hand without AI.
Appointment report
Pick a period (7, 30 or 90 days) and Koharu creates a PDF to hand to your doctor: severity over time, the monthly log, symptoms, medications and changes, sleep, heart rate and air pressure, patterns in your records, and daily records. Every number is counted from your records on your iPhone, never by the AI. Appointment reports are part of Premium.
How patterns are found
After 14 days of records, Koharu compares your severity with pressure drops, sleep, heart rate variability, steps, triggers and medication changes using statistical tests on your iPhone (a permutation test that shuffles 7-day blocks, with a correction for making many comparisons). Only clear differences are shown as a "Likely pattern". Patterns summarize your records; they do not show causes.
When you write urgent words
If you write words such as "sudden severe headache" or "slurred speech", Koharu shows emergency and crisis lines such as 119 in Japan and 911 in the US right away, without waiting for the AI reply, even when you are offline. Numbers and hours are in the list of crisis lines.
Medications and reminders
A list of what you take, dose check-offs and reminders at the times you set. You can also log as-needed medications. For medications added from an Okusuri Techo QR code, the first dose times are set from the directions, such as "after breakfast" or "at bedtime". You can change the times later.
Daily check-ins
At the time you choose, Koharu sends a reminder to log how today went. You can change the time later in Settings → Notifications.
How your data is handled
- Your records are saved only on your iPhone. They are not synced with iCloud and not stored on our server. No account is needed.
- The Okusuri Techo QR code is read on your iPhone. Camera images and photos are never saved or sent, and the name, date of birth, clinic and doctor in the code are not read.
- Only with your consent, your conversation is sent to an AI provider in the United States (OpenAI) to write Koharu's replies. Your name is not sent, and it is not used to train AI models. Without consent, you can still log by hand.
- Sleep, heart rate and steps from Apple Health are read only if you allow it. Koharu never writes to Apple Health.
- No ads. We never sell your data.
- Settings → Delete all data deletes the records on your iPhone and records such as usage counts on our server.
Before you start
Koharu is not a medical device and is not intended to diagnose, treat or prevent any disease. Talk to your doctor about your health and medications.
In an emergency, call your local emergency number (911 in the US, 119 in Japan) right away. Koharu is for people aged 18 and over.