Methodology

Every number on this site is computed directly from the NIH Dietary Supplement Label Database (DSLD), as of the January 2026 dump (214,780 labels ever ingested, 121,959 currently on-market).

Ingestion

We download DSLD's full-database JSON dump directly (confirmed link on dsld.od.nih.gov/api-guide) and parse every label into a relational schema: products, brands, ingredient rows, proprietary blends, other ingredients (excipients), and label statements. The last dump parsed 214,780 labels with a 100% parse success rate.

Normalization

Raw label ingredient names and forms are matched to a curated set of 40 canonical compounds and their common forms via exact alias matching, regex qualifier-stripping, and fuzzy matching (rapidfuzz, ≥92 similarity). Anything that doesn't clear that bar is left unmatched and routed to a review queue rather than guessed. The same pipeline matches excipients against a curated alias table of 155 common carriers, colors, and sweeteners.

Elemental amount conventions

When a label declares an ingredient by its bare element/vitamin name (the common case, e.g. "Magnesium"), we treat the declared amount as already elemental, per longstanding FDA labeling rules. When a label declares the salt itself as the ingredient name (e.g. "Magnesium Oxide"), we convert using that form's elemental fraction (computed from molecular weight stoichiometry, with the assumed hydration state documented per form). Blend members with an undisclosed amount are recorded as such — never estimated. Full conventions, including unit conversions (IU→mcg for vitamin D, DFE for folate), are documented in our reference data.

Form quality tiers

Tier 1 (best-evidenced bioavailability), Tier 2 (acceptable), and Tier 3 (low-cost/low-bioavailability) ratings are based on published comparative bioavailability or clinical-outcome literature specific to that form, cited on each compound's "forms explained" section. Where no comparative study was found, the form is left unrated (null) rather than guessed.

What DSLD is and isn't

• DSLD is survey-sourced plus voluntary manufacturer submissions — it is not a market census, and coverage of any given retailer or brand is not guaranteed to be complete.
• Off-market status can lag real-world retail availability.
• Every value is manufacturer-declared on the label as submitted to DSLD, not independently lab-tested or verified by us or by NIH.
• Statement-type bucketing (claim/warning/identity/other) is a heuristic based on DSLD's own descriptive type strings, not a legal classification.

No health advice

Supplement Label Index does not rate, score, or recommend products, and nothing on this site is medical or nutritional advice. It reports what labels declare and what the market does. Consult a qualified healthcare professional for guidance on your own supplementation.

Refresh cadence

Data is refreshed monthly: a new DSLD dump is ingested, diffed against the prior month, and all metrics and reports are recomputed.