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Standards

Evidence grades

A grade describes the best type of study we found for a compound and a specific use. It says nothing about safety, and a higher grade for one use does not carry over to another.

  1. Grade 1: Cell studies

    Results come from cells or tissue in a dish. Useful for mechanism, weak for predicting effects in a living body.

  2. Grade 2: Animal studies

    Results come mainly from rodents or other animals. Doses, routes and outcomes often do not translate to people.

  3. Grade 3: Early human data

    Small, short or uncontrolled human studies, case series or safety pilots. Promising signals, not proof.

  4. Grade 4: Controlled human trials

    At least one randomised, controlled trial in people for a specific use. The strongest grade we give.