I built Healstack because I take more than one supplement, and I could never actually picture how they overlapped in time. Two things taken on the same calendar day feel unrelated until you realize they were both active in your body at 3pm. That overlap is exactly where interactions live, and nobody keeps that timeline in their head. Healstack logs a dose in two taps, then derives your "active stack" from duration windows instead of storing it separately, so it's always correct for right now without any background job. Log something and it checks against everything still active before the entry saves, not after, because a warning after you've already taken the dose can't change anything. Under that sits a library of 200 substances with harm-reduction notes I wrote by hand, plus daily check-ins, biometrics, a heatmap of patterns over time, and lab results in and out of range. It's on the web and iPhone. Auth and storage run on Supabase, row-level-security scoped per user, so nobody else can read your dose history. No analytics, no trackers. Would love feedback on the interaction warnings especially. That's the part I care most about getting right. Free on iPhone and the web, with a $1 one-time CSV export on the web.

Machaon

Track what you take, and what it does

Track what you take, and what it does