Scoring Methodology
Transparency is core to what we do. Here is exactly how we score every supplement product in our database. Our methodology is designed to be rigorous, reproducible, and independent of any brand relationship.
Overall Score: Letter Grade (A+ through F)
Every product receives an overall letter grade that is a composite of four equally-weighted sub-scores. Each sub-score accounts for 25% of the total. We believe these four pillars capture everything a consumer needs to make an informed supplement purchase.
1. Evidence Score (25%)
How strong is the clinical evidence that this supplement works for its primary claimed benefit? We prioritize systematic reviews and meta-analyses of randomized controlled trials (RCTs). Animal studies and in-vitro research alone are not sufficient for a high evidence score.
| Grade | Criteria |
|---|---|
| A | Multiple large RCTs, systematic reviews/meta-analyses confirming benefit. Consistent results across studies with meaningful effect sizes. |
| B | Several RCTs showing benefit, generally consistent results. Good evidence base but may have some limitations in study design or sample size. |
| C | Limited RCTs, mixed results, or primarily observational studies. Evidence is suggestive but not conclusive. |
| D | Very limited evidence, mostly animal or in-vitro studies. Human data is scarce or poorly designed. |
| F | No meaningful evidence of benefit, or evidence actively suggests the supplement does not work for its claimed purpose. |
Sources we use: PubMed systematic reviews, Cochrane Library, Examine.com research summaries, NIH Office of Dietary Supplements fact sheets, Natural Medicines Comprehensive Database.
2. Quality & Purity Score (25%)
Is the product what it says it is? Is it free from contaminants? Third-party testing is the gold standard because it means an independent lab has verified the product's contents and purity.
| Grade | Criteria |
|---|---|
| A | USP Verified OR NSF Certified for Sport, plus additional third-party testing. The highest tier of quality assurance available. |
| B | Third-party tested by a recognized body (ConsumerLab approved, Informed Choice, BSCG certified). Verified but not at the USP/NSF tier. |
| C | GMP certified manufacturing facility, but no independent third-party product testing. OR third-party tested with minor issues noted. |
| D | No third-party testing visible, no GMP certification displayed. Quality assurance is unclear or unverified. |
| F | Failed third-party testing, or known contamination/mislabeling issues. Active quality concerns. |
Sources we check: NSF certified product database, USP verified product list, ConsumerLab reviews (publicly available pass/fail), BSCG certified database, Informed Choice database.
3. Value Score (25%)
This is the metric that separates us from every other supplement review site. We calculate cost per clinically effective daily dose - not cost per pill, not cost per serving. If a clinical trial used 600mg of ashwagandha and a product only contains 300mg per capsule, you need two capsules to reach the effective dose. We calculate accordingly.
| Grade | Criteria |
|---|---|
| A | Bottom 20% of cost per effective dose in its category. Excellent value for the quality delivered. |
| B | Below median cost per effective dose. Good value relative to alternatives. |
| C | Near median cost per effective dose. Neither a bargain nor expensive. |
| D | Above median cost per effective dose. You're paying a premium without a clear quality justification. |
| F | Top 20% most expensive per effective dose, OR the product is so underdosed that reaching the effective dose at the recommended serving is impossible or impractical. |
How We Calculate Cost Per Effective Dose
1. Identify the clinically effective daily dose from published RCTs and meta-analyses.
2. Determine how many servings of the product it takes to reach that dose.
3. Calculate: (Price / Servings per container) x Servings needed = Cost per effective dose per day.
Example: Ashwagandha KSM-66
Clinical dose: 600mg/day | Product: 300mg/capsule, 90 capsules, $19.99
Servings needed: 600/300 = 2 capsules/day
Cost per serving: $19.99/90 = $0.222
Cost per effective dose: $0.222 x 2 = $0.44/day
4. Transparency Score (25%)
Does the label tell you exactly what you're getting? Proprietary blends that hide individual ingredient amounts are a red flag. We believe you have the right to know exactly what's in your supplement and how much of each ingredient you're taking.
| Grade | Criteria |
|---|---|
| A | Full ingredient disclosure, no proprietary blends, specific forms identified, source identified, third-party certification prominently displayed. |
| B | Full disclosure with minor gaps (e.g., source not specified but form is clearly stated). |
| C | Uses proprietary blend but key active ingredients appear to be dosed adequately based on available information. |
| D | Proprietary blend hiding key ingredient amounts. Impossible to determine if you're getting effective doses. |
| F | Misleading label, undisclosed ingredients, or deceptive marketing claims. |
Our Data Sources
NIH Dietary Supplement Label Database
207,000+ verified product labels for ingredient verification
NIH Office of Dietary Supplements
Evidence summaries per nutrient from the federal government
PubMed
Systematic reviews and meta-analyses for evidence scoring
Examine.com
Research summaries used as starting points, always verified against primary sources
USP Verified Product List
Gold standard for third-party quality verification
NSF Certified for Sport Database
Quality verification trusted by professional athletes
ConsumerLab.com
Publicly available pass/fail results for product testing
BSCG Certified Database
Banned substance testing and quality verification
Informed Choice Database
Sports supplement testing and certification
Amazon & Brand Websites
Current pricing data, verified regularly
Our Research Workflow
For every supplement type we cover, we follow a standardized six-step process:
- 1
Identify the clinically effective dose from meta-analyses and the highest-quality RCTs available.
- 2
Identify the best-absorbed forms from bioavailability research.
- 3
Pull the top 8-15 products from Amazon bestsellers and recommended brands.
- 4
For each product: record ingredients, doses, and forms from the label (DSLD or brand site). Check third-party testing status. Record current price and servings per container. Calculate cost per clinically effective dose. Assess label transparency.
- 5
Score each product on our four-factor rubric.
- 6
Write up the evidence summary from primary research and compile the full scorecard page.
Our Independence Guarantee
Affiliate relationships never influence our scores. We earn commissions when you purchase through our links, but every product is scored using the same rubric regardless of whether we have an affiliate relationship with the brand. Many of our highest-scored products are from brands we have no affiliate relationship with.
If we discover an error in our scoring, we update the page and note the correction. Our goal is accuracy, not selling supplements. If a supplement doesn't work, we'll tell you. If a popular product is overpriced or underdosed, we'll say that too.