Can a phone app measure blood pressure?

Short answer: no. A phone cannot reliably measure blood pressure or blood sugar with its camera, flashlight or fingerprint sensor. Apps that promise this give numbers you should not trust. Measure with a validated upper-arm cuff monitor or a glucose meter, and use an app only to log the results.

1. Why fingertip apps don't work

Blood pressure is measured by squeezing an artery with a cuff and reading the pressure. A camera can only see small color changes in your fingertip, which is not enough to calculate pressure. Reviewers of such apps report readings that "75% of the time" did not match their own monitor, and a phone that gets "unbearably hot" with a finger on the camera. The American Heart Association recommends a validated, automatic upper-arm cuff monitor for home use.

2. What about blood sugar?

There is no way to measure glucose through a phone screen or camera. You need a finger-prick glucose meter or a continuous glucose monitor (CGM). Some CGMs send data to a phone app, but the measuring is done by the sensor, not the phone.

3. What a good log app does

• Lets you type the numbers from your monitor quickly.
• Keeps date, time and context (morning, fasting, after meal).
• Shows averages and trends and exports a file for your doctor.
• Does not take over your home screen or show ads outside the app.

Doing it with Readband

Readband says it plainly: it does not measure. You type the numbers from your BP monitor or glucose meter in about 3 seconds, and Readband keeps 7/30/90-day charts, averages, a reference color band (based on public AHA and ADA guidance, for reference only) and a CSV for your doctor. No account, no launcher changes.

For reference only. This guide does not diagnose or treat anything. Targets differ from person to person; follow your doctor or care team.

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