Enzymedica UK: 3.4% to 16.9% conversion on a single Black Friday weekend

The challenge

Enzymedica UK is a Shopify-based health-supplements brand. The Black Friday window is the most revenue-concentrated weekend of the year for the category. The prior year's Black Friday had run at roughly 7% conversion. Baseline outside that window sat at 3.4%.

The brief was straightforward: maximise Black Friday conversion without increasing ad spend.

The constraint was real. December is the worst month of the year for health supplements (post-Christmas guilt cycle suppresses purchase intent). Any winner deployed during the engagement had to hold up against that headwind, not just spike during the promo.

What I did

A 30-day engagement, three compounded CRO wins shipped in sequence:

1. Pricing-page anchor restructure. The multi-pack product tiers had the highest tier discounted aggressively, undermining the anchor for the middle tier. Audience-hypothesis review and quantitative funnel data confirmed the issue. Re-tested with a different anchor structure. Winner shipped at 99% confidence (The 99 Rule) inside the first week.

2. Add-to-cart flow simplification. Heatmap data and session recordings surfaced rage-click patterns on the variant selector. Layer 3 evidence (heatmap) plus Layer 4 evidence (post-purchase survey verbatim) ranked the hypothesis high enough to ship ahead of cosmetic tests in the queue. Winner sustained.

3. Trust-element relocation. Customer-review widget had been inserted below the fold. A/B test moved it directly above the price-tier block. Winner held through the cold-traffic spike of Black Friday weekend — when trust signals matter most.

Each test was operator-set against expected revenue impact. Each winner was gated at 99% statistical significance. Each losing variant was logged with a hypothesis-failure-mode tag for future reference. The full Evidence Stack running on every test.

The outcome

• Black Friday conversion: 16.9% (vs 3.4% baseline, 7% prior-year Black Friday)
• 5× lift on the same promo day, same product range, same audience
• 11% conversion sustained through December — the toughest month for health supplements
• The 30-day engagement pre-paid for itself within the Black Friday weekend alone

What this case proves

The 4-to-34 Gap is real even on stores with mature CRO programmes. Enzymedica had been running tests with prior agencies. The 7% prior-year Black Friday was already 2× a generic ecommerce baseline. Moving from 7% to 16.9% on the same promo day required all four Evidence Stack layers running in sequence — operator-set hypotheses, sample-size discipline, 99% winner-call, failure-as-information feeding the next test.

The same playbook is the engine of every Growth retainer engagement.