What is DayByDay?
DayByDay is a patient-facing wellness tracking application designed for individuals managing weight loss, often in the context of GLP-1 medication therapy. It is a personal tracking tool — not a medical device, not FDA-cleared, and not designed for clinical or diagnostic purposes. All data is self-reported and should be interpreted accordingly.
DayByDay helps patients stay consistent with logging their weight, medications, sleep, activity, and body measurements between clinical appointments. The goal is to give patients a clearer picture of their own progress and to facilitate more informed conversations with their care team.
Not a medical device
DayByDay is not FDA-cleared, CE-marked, or approved for diagnostic, clinical decision support, or therapeutic use. Data generated by DayByDay should not be used as the sole basis for clinical decisions. All information should be verified clinically where relevant.
What your patient can track
DayByDay covers the following data categories. All entries are patient-initiated — either logged manually or synced from Apple Health or a compatible wearable.
| Category | What's tracked | Source |
|---|---|---|
| Weight | Daily weigh-ins, smoothed trend line, body fat percentage | Manual entry or Apple Health |
| GLP-1 medication | Dose date, medication name, dose amount (mg), injection site, notes | Manual entry |
| Sleep | Total sleep time, sleep stages (REM, core, deep, awake), SpO2, dips per hour, heart rate, respiratory rate | Apple Health (Apple Watch), O2 Ring (Wellue/Viatom) |
| Exercise & activity | Daily steps, active calories, exercise minutes, resting heart rate | Manual entry or Apple Health |
| Body measurements | Waist, chest, and neck circumference; clothing sizes | Manual entry |
| Lab values | HbA1c, fasting glucose, total cholesterol, LDL, HDL, triglycerides | Manual entry |
The health report PDF
Your patient can generate a PDF health report directly from the DayByDay app. The report is designed to be reviewed quickly during a clinical appointment and covers a date range of your choosing.
A typical report includes:
- ✦Weight trend chart — raw daily weigh-ins with a smoothed trend line, total weight change, and rate of loss over the selected period.
- ✦GLP-1 medication log — chronological list of doses with date, medication, and dose amount.
- ✦Sleep summary — average total sleep time, sleep stage distribution, average SpO2, and dips per hour (if O2 Ring or Apple Watch data is available).
- ✦Body measurements — waist, chest, and neck with change from baseline.
- ✦Lab results — HbA1c, fasting glucose, lipid panel, with dates and any patient-entered notes.
- ✦Key statistics — BMI, BMR estimate, RFM, WHtR, and FFMI where sufficient data exists.
Report data is self-reported
All values in the PDF are entered by the patient or synced from consumer wearables. Lab values in particular are self-transcribed and have not been verified against a reference laboratory. Treat them as patient-reported values, not confirmed laboratory results.
How to request a report from your patient
Ask your patient to follow these steps before their appointment:
- 1Open DayByDay on their iPhone or at web.mydaybyday.app.
- 2Tap Reports in the navigation.
- 3Tap Generate PDF.
- 4Select a date range (for example, the last 3 months or since their last visit).
- 5Tap Generate.
- 6Use the share sheet to email the PDF, AirDrop it, or save it to print.
Suggested date ranges
For a follow-up appointment, a 30- to 90-day report typically provides the most clinically useful view of weight trend, medication adherence, and sleep patterns. The all-time report is useful for evaluating overall progress since the patient started their weight loss journey.
Important limitations
Please keep the following in mind when reviewing data from DayByDay.
GLP-1 medication levels are estimates only
The medication level displayed in DayByDay is calculated from pharmacokinetic half-life data using an exponential decay model. It is not a serum drug concentration measurement. Individual variation in absorption, metabolism, renal function, and body composition means actual drug levels will differ from the estimate. Do not use this value for clinical dose adjustments.
Blood oxygen data from consumer wearables is not medical-grade
SpO2 readings in DayByDay come from an O2 Ring (Wellue/Viatom) or Apple Watch. These are consumer-grade optical sensors, not certified pulse oximeters. They may underperform in patients with darker skin tones, poor peripheral perfusion, nail polish, or significant motion artifact. Any clinically significant SpO2 finding should be confirmed with a calibrated medical-grade oximeter.
- ✦Weight entries are self-reported and depend on patient consistency and scale calibration.
- ✦Sleep stage data from Apple Watch uses accelerometry and heart rate — it is an approximation, not polysomnography.
- ✦Lab values are manually transcribed by the patient from their own lab results. Cross-reference with your laboratory records.
- ✦Body measurements are self-measured with a tape measure. Technique varies between patients.
- ✦All calculated metrics (BMI, RFM, WHtR, FFMI, BMR) are population-level estimates and should not replace direct body composition measurement in clinical contexts.
Privacy of patient data
Patient data in DayByDay is encrypted in transit (TLS) and at rest (AES encryption via Supabase PostgreSQL on US-based servers). Row-Level Security policies ensure that no user can access another user's records at the database level.
DayByDay does not share patient health data with third parties for commercial purposes. The only third-party processors with access to data are Supabase (database hosting) and RevenueCat (subscription billing — billing status only, not health data). Apple Health data is processed on the patient's device and does not pass through any additional third party.
Patients retain full ownership of their data and can delete it permanently at any time. DayByDay does not have a HIPAA Business Associate Agreement (BAA) in place, and the app is not currently designed for use in covered entity workflows.
No BAA / Not HIPAA-covered
DayByDay does not currently offer a HIPAA Business Associate Agreement. It is designed as a patient-facing consumer wellness application, not a clinical or EHR-integrated tool. It should not be used to store, transmit, or process Protected Health Information (PHI) on behalf of a covered entity.
Clinical questions and contact
If you have questions about DayByDay's data methodology, formula references, or the source of any specific calculation shown in a patient report, we're happy to assist.
Email us at support@mydaybyday.app with "Provider inquiry" in the subject line. Please include the specific metric or calculation you have a question about and we will respond with the full methodology and any relevant citations.
Important notice for healthcare providers
DayByDay is a personal wellness tracking application and is not intended to be used as a medical device, diagnostic tool, or clinical decision support system. Data generated by DayByDay is self-reported by patients using consumer hardware and software. All values, estimates, and metrics should be interpreted in the context of a complete clinical evaluation by a qualified healthcare provider. DayByDay assumes no liability for clinical decisions made based on data presented within the application or its exported reports.