Our scoring methodology

Every supplement reviewed on Health Britannica is scored using the same 6 proposition value metrics. This page explains exactly how we arrive at each score — so you can evaluate our recommendations with full transparency.

The 6 metrics

Evidence (0-10)

We evaluate the quality and quantity of clinical research supporting the supplement's claimed benefits. Scoring hierarchy: Systematic reviews/meta-analyses (highest) > randomized controlled trials > observational studies > animal studies > mechanistic/in-vitro > anecdotal. A score of 9+ means multiple human RCTs with consistent results. Below 6 means mostly animal/mechanistic evidence.

Purity (0-10)

Does the bottle match the label? We check for third-party certifications (NSF, Informed Sport, USP, ConsumerLab), heavy metal testing, label accuracy reports, and manufacturing standards (cGMP compliance). A 9+ means independently verified with published COAs.

Value (0-10)

Cost per clinically effective dose compared to alternatives in the same category. We calculate cost-per-serving at the researched dose (not the label dose if they differ). Premium brands can still score high on value if no cheaper equivalent exists at the same quality.

Efficacy (0-10)

Does the product deliver the researched dose in a bioavailable form? Many products contain the right ingredient at the wrong dose, or in a poorly absorbed form. We compare label doses to clinically studied doses and evaluate the delivery form.

Safety (0-10)

Side effect profile, drug interaction potential, and long-term safety data. We take a conservative approach — if long-term data is lacking, the score reflects that uncertainty. Known interactions with common medications are noted.

Synergy (0-10)

How well the supplement integrates with other products in its stack(s). Does it enhance absorption of cofactors? Does it have timing conflicts? Does it fill a unique role or overlap with something cheaper?

Score thresholds

Editorial independence

Our scores are never influenced by affiliate relationships. We frequently recommend budget options (NOW Foods, Nutricost) that pay lower commissions because they're genuinely the best value. No brand can pay for a higher score or preferential placement.