Glossary

Definitions for the measurement terms used across our evidence tables, written to be checked rather than skipped.

• Bioavailability — The fraction of a dose that reaches the bloodstream unchanged. The reason a milligram figure on a label cannot be read as a dose.
• Confidence Interval — The range a true effect plausibly occupies. The single most useful number on this site, and the one most often left out of supplement marketing.
• Randomised Controlled Trial — The study design that supports a causal claim. Why a supplement trial's controls matter more than its size.