This is the part I use most. Every treatment has three steps, and the app follows them.

Pre-treatment form with weight, fluid goal, blood pressure and pulse fields, plus medication carry-over toggles
Before: vitals and goal. (Synthetic data.)
Active session screen with a running timer and a list of timed readings taken during treatment
During: timed readings as it runs.
Post-treatment summary with final weight, blood pressure, duration and totals
After: the summary writes itself.

Before

I enter my weight and a couple of vitals. The fluid goal and rate auto-calculate from my dry weight — but every field stays editable, because real days don't match the formula. Medications I take during treatment carry over so I don't re-enter them.

During

The session screen shows a timer and a running list of readings. I add a reading and it's saved instantly — no spinner, no "are you sure". Mid-treatment is the worst time to fight an app, so the writes happen on the device and sync later.

After

At the end, the summary is mostly already filled: duration, totals, final vitals. I confirm it and it joins the history on the home screen.

That's the whole loop. The design rule was simple: auto-fill everything, but never lock me out of correcting it. A tool that argues with you when you know better doesn't get used.

Next in the series: turning two years of these numbers into trends I can actually read.