How We Score
Every supplement we cover is scored on six metrics, 0-10 each, for a maximum of 60 points. Overall scores on roundups are the simple average (so max 10). The rubric is public, weighting is public, and every product's score per metric is shown on its scorecard.
The 6 metrics
1. Third-party testing
What we look for: Independent verification that the product contains what the label claims and no undisclosed contaminants. USP Verified, NSF Certified, NSF Certified for Sport, and Informed Sport are the strongest consumer-facing marks. Published Certificates of Analysis (COAs) from reputable labs are a good secondary signal.
How we score: 10 for NSF Certified for Sport or USP Verified; 7-9 for Informed Sport or published per-batch COAs; 4-6 for brand-published in-house testing only; 0-3 for no verifiable testing.
2. Bioavailability
What we look for: Forms and delivery methods with strong absorption evidence. This varies by nutrient — chelated minerals over oxides, methylated B vitamins over their cyanocobalamin counterparts, triglyceride-form omega-3 over ethyl ester, hydrolyzed collagen peptides over non-hydrolyzed.
How we score: 10 for the form with the strongest published bioavailability evidence for its class; 5-7 for mid-tier forms; 0-3 for forms with poor or contradicted absorption evidence (e.g., magnesium oxide, cyanocobalamin in MTHFR populations).
3. Clinical evidence
What we look for: Published randomized controlled trials using the specific extract, form, or formulation at the product's dose. A generic "magnesium supplement" can't claim a KSM-66 ashwagandha's research profile. Strain-specific (for probiotics), extract-specific (for botanicals), and form-specific (for vitamins) evidence counts higher than generic category research.
How we score: 10 for multiple RCTs using the exact extract/strain/form at the product's dose; 7-9 for strong category evidence but less specific; 4-6 for weaker or preliminary evidence; 0-3 for claims not supported by controlled trials.
4. Value
What we look for: Price per effective dose — per-elemental-gram for minerals, per-gram-protein for protein powder, per-5g-serving for creatine. Not price per bottle or per scoop, which hides the real cost comparison.
How we score: 10 for meaningfully-below-category cost per effective dose with no quality tradeoffs; 5-7 for mid-range; 0-3 for premium-priced products whose cost isn't justified by differentiated quality.
5. Brand transparency
What we look for: Full ingredient disclosure (no "proprietary blends" hiding doses), published COAs, sourcing transparency, honest communication about what research the brand's claims actually rest on.
How we score: 10 for full transparency (every ingredient, dose, source, test result public); 4-6 for partial disclosure; 0-3 for heavy use of proprietary blends or impossible-to-verify sourcing claims.
6. Form & absorption
What we look for: Delivery format matched to the nutrient — softgel with fat for fat-soluble vitamins, capsule for most water-soluble actives, powder for protein and electrolytes. Gummies are usually a compromise (omit iron, short shelf life for fat-solubles). Timed-release technologies and enteric coatings where they're genuinely functional.
How we score: 10 for format that genuinely matches nutrient needs; 5-7 for serviceable format; 0-3 for format choices that undermine the product's effectiveness.
How we pick products to include
We start with the best-selling products in each Amazon category, then filter for: available with working Amazon listings, within our scoring rubric criteria, and representative of the category's quality range. We include both budget and premium options so the roundup is useful regardless of budget.
If a product has a known quality issue (failed independent tests, recalls, well-documented mislabeling), it's excluded even if it sells well.
How often we re-score
Rankings are re-verified quarterly. Products change — new formulations, new certifications, ingredient swaps, discontinuations, and shifting pricing all affect scoring. The "Last verified" date on every roundup shows when the scoring was last checked. Corrections and changes are published transparently, not silently.
What this rubric doesn't tell you
A top-rubric-scored product may still not be the right choice for you. Our rubric reflects quality and evidence — it cannot tell you whether a specific supplement is appropriate for your specific health situation. That's what a physician or registered dietitian is for. Use our reviews as a shortlist, not as medical advice.