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13 Comments

I tested Retatrutride pen in the UK

Been researching UK research peptides for a personal metabolic project. Assumed pre-filled pens would be 3-4x the vial price. They're not.

Once you factor in bac water, syringes, and 20+ minutes of reconstitution per prep, the actual delta is closer to 20-30%. For retatrutide specifically, some UK suppliers are aggressive on pen pricing at volume.

Filters I used across 6 suppliers:

  • ISO-accredited batch report
  • HPLC purity above 99%
  • Cold-chain UK dispatch (not "UK site, ships from Riga")

The pen standout was a UK Reta pen supplier doing 40mg pens at £129 single / £99 at 10+, ISO/IEC 17025 lab, 99.68% purity, 24h dispatch.

The "small friction that compounds weekly" we preach about eliminating in our businesses is also worth eliminating in personal routines. Evenings are worth the £20.

Anyone else made the vials → pens switch?

on September 24, 2026
  1. 1

    Thanks for sharing the numbers, that makes it much easier to follow.

  2. 1

    Nice progress. What is the next thing you are focusing on?

  3. 1

    Good write-up. What would you do differently if you started again?

  4. 1

    Clear and practical, thanks. Did anything surprise you along the way?

  5. 1

    Curious how long it took before you saw the first real results?

  6. 1

    Great breakdown. What feedback have you had from early users?

  7. 1

    How did you decide this was worth building in the first place?

  8. 1

    Curious how long it took before you saw the first real results?

  9. 1

    Appreciate the honesty here, most people only share the wins.

  10. 1

    Good point. Did you test that with users before committing to it?

  11. 1

    Solid lesson. Which channel has worked best for you so far?

  12. 1

    Makes sense. Are you planning to charge for it, or keep it free for now?

  13. 1

    This is great work — reminds me of some of the calls I've had to make building Xstream4K. What would you do differently if you started over?