This is arithmetic, not advice
It costs a plan you describe to it. It has no opinion on whether that plan is sensible, and it cannot tell whether your dose is appropriate for you. Retatrutide is not licensed by the MHRA and has no approved UK dosing. Nothing here is medical advice — consult a qualified healthcare professional.
Every kit size, costed against your plan
Delivered prices include flat shipping and the payment fee, spread over one order. "Vial lasts" is at your maintenance dose.
| Kit | Per vial | You'd need | Delivered | £/mg | Vial lasts |
|---|
Why the cheapest kit is usually the wrong one
Peptide gets dramatically cheaper per milligram as the kits get bigger — the largest is about a fifth the price per mg of the smallest. Every cost guide you'll read stops there and tells you to buy in bulk.
The problem is that the bigger kits get cheaper by putting more milligrams in each vial, and a vial only lasts four to six weeks once it's mixed with bacteriostatic water. At 4mg a week, a 20mg vial is used up in exactly five weeks. A 30mg vial would take seven and a half — so you'd be pouring the last third away.
That's the constraint this calculator applies and most don't. It only recommends kits whose vials you can finish inside the window, and it shows you the cheaper ones you can't use so you can see why. The full workings are in the mixing guide and the resources page.
What the numbers rest on
The kit prices are the ones I was quoted, converted at the rate I actually paid — $155 for 200mg plus $50 postage plus a 5% payment fee, which came off my card as £168.63. That's £0.84 a milligram all in, and the full receipt is on the resources page.
Two assumptions worth knowing. Shipping is treated as a flat charge per order, which is what I was charged — but that's one receipt, not a published tariff, so a very large order might be different. And the titration model steps up 1mg at a time from 1mg to your maintenance dose. That reproduces the 4mg and 6mg schedules in the 12-month protocol exactly — 184mg and 252mg. The 8mg route there ramps to 6mg and then jumps, so this comes out 4mg lower at 304mg rather than 308mg; it makes no difference to which kit you buy or what it costs. Change the step field if your ramp is different.
For converting a vial into millilitres and syringe units once it arrives, use the dose calculator.