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Methodology

How Null Health builds, labels, and (eventually) vets every formula on the site.

Current state: arithmetic placeholders

Every formula currently in production is a transparent arithmetic conversion - things like mg_per_injection = weekly_mg / doses_per_week. They do not model pharmacokinetics, ester half-life, peak/trough behaviour, body composition, or any patient-specific variable. Every formula is labelled placeholder on its calculator page until it has been clinician-reviewed.

Where the formulas come from

The placeholder formulas come from public, well-documented arithmetic relationships:

  • Doses per week from the calendar (7 days divided by the chosen interval).
  • Volume per injection from the standard concentration relationship volume = mass / concentration.
  • U-100 syringe units from the standard insulin-syringe convention 1 unit = 0.01 mL (100 units = 1 mL).
  • Doses per vial from the integer floor of vial volume divided by per-injection volume.

How a formula leaves placeholder status

  1. 1. Source review. A formula is grounded in a specific, citable source (FDA labelling, clinical guideline, or peer-reviewed reference).
  2. 2. Test coverage. The formula is exercised by unit tests covering at least the documented edge cases.
  3. 3. Clinician sign-off. A licensed clinician reviews both the formula and the surrounding copy, including the FAQ.
  4. 4. Public dated review. The page records who reviewed it and on what date. The placeholder badge is removed.

Per-calculator details

The full assumptions list lives on each calculator page itself:

Privacy

Calculators run entirely in your browser. Inputs are stored in local storage on your device so the form remembers what you typed; nothing is transmitted to any server, and inputs are not logged. Shared URL state (e.g. links containing ?weeklyMg=...) is purely a convenience for sharing setups - it does not get logged either.