Calculator for retatrutide reconstitution and per-administration dosing maths. Retatrutide is supplied predominantly in prefilled research pen format (10–45mg per pen on the standard 3ml/300-click platform); some research-grade vial preparations exist.
For research and educational purposes only. This calculator performs volumetric mathematics on the values you enter; it does not recommend doses or provide medical advice.
Universal peptide & nootropic dose calculator
Standard research pen format: 3 mL total volume, 300 clicks per pen. That’s fixed — so the only thing that changes is how many mg are in your specific pen. mg per click = your pen’s mg ÷ 300.
Vial mode: most research peptide vials are 3 mL borosilicate glass (industry standard — about 99% of compounds ship in this size). Larger compounds like NAD+ or high-mg GHK-Cu sometimes come in 5–10 mL vials. The bacteriostatic water you add must fit inside your physical vial — for a standard 3 mL vial, that’s usually 1–3 mL of BAC water. Tell us the vial’s peptide content (in mg), the BAC water you added, and your target dose — we work out the concentration, the volume to draw, and the syringe units on a U-100 insulin syringe.
Research and educational purposes only. Not medical advice. Not for human consumption. This calculator performs volumetric mathematics on the values you enter; it does not recommend doses. Compounds listed are not licensed as medicines for human use unless stated otherwise.
About Retatrutide
Retatrutide is not licensed as a medicine in the United Kingdom. It is an investigational GLP-1/GIP/glucagon triple receptor agonist currently in clinical development. As of mid-2026 it has no marketing authorisation from the MHRA or EMA. Retatrutide is supplied as a research-grade compound; it is NOT available through licensed UK pharmacy channels. Stackcalc.co.uk does not sell retatrutide and this calculator is provided for information and research-mathematics purposes only.
Published research literature describes retatrutide in clinical trials for obesity and metabolic conditions. The compound’s triple-agonist mechanism (GLP-1, GIP, and glucagon) is the subject of ongoing Phase 3 investigation.
Typical reconstitution / pen formats
| Format | BAC water | Concentration / mg per click | Volume to draw / clicks | For |
|---|---|---|---|---|
| 20mg pen (prefilled, 3ml/300 clicks) | — | 0.067 mg/click | ≈30 clicks for 2mg / ≈37 clicks for 2.5mg | industry-standard format |
| 30mg pen (prefilled, 3ml/300 clicks) | — | 0.10 mg/click | ≈20 clicks for 2mg / ≈25 clicks for 2.5mg | industry-standard format |
| 40mg pen (prefilled, 3ml/300 clicks) | — | 0.133 mg/click | ≈15 clicks for 2mg / ≈19 clicks for 2.5mg | industry-standard format |
Retatrutide dosing observed in research literature
Retatrutide is a long-acting weekly compound. Published clinical-trial titration protocols escalate from approximately 2mg per week up to a target maintenance of 8–12mg per week over a multi-month titration period.
These figures are reported here for completeness of the research-literature picture and do not constitute a dosage recommendation.
Half-life and frequency
Retatrutide has a half-life of approximately 6 days, supporting once-weekly administration. This is comparable to semaglutide (≈7 days) and longer than tirzepatide (≈5 days).
Storage and shelf life
Prefilled research pens are typically supplied pre-reconstituted and stored refrigerated at 2–8°C. Manufacturer’s COA provides specific shelf-life data.
Frequently asked questions
Is retatrutide legal in the UK?
Retatrutide is not a controlled substance under the UK Misuse of Drugs Act 1971. However, it is also not licensed as a medicine in the UK — it has no marketing authorisation from the MHRA or EMA. Stackcalc.co.uk does not sell retatrutide. The compound is supplied for research-grade laboratory use only.
How is retatrutide typically dosed in research?
Weekly subcutaneous administration is the predominant pattern described in clinical-trial literature. Titration from approximately 2mg/week up to maintenance doses of 8–12mg/week over several months is the published protocol.
How many clicks per dose on a 40mg pen?
40mg ÷ 300 clicks = 0.133mg per click. For a 2mg target: 2 ÷ 0.133 ≈ 15 clicks. For 2.5mg: ≈19 clicks. For 4mg: ≈30 clicks.
What’s the difference between retatrutide and semaglutide?
Both are GLP-1-active compounds. Retatrutide is a TRIPLE agonist (GLP-1 + GIP + glucagon receptors). Semaglutide is a single GLP-1 receptor agonist. Tirzepatide is a dual agonist (GLP-1 + GIP).
Why does the calculator show retatrutide if it’s not for sale in the UK?
The calculator is provided for research and educational purposes. Researchers using retatrutide as a research-grade compound need accurate dosing mathematics. The fact that the compound is investigational and not for sale in the UK does not change the underlying volumetric maths the calculator performs.
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Where to source research-grade Retatrutide
For UK readers researching Retatrutide, our partner supplier stocks research-grade preparations. (Partner link to be added after the affiliate arrangement is signed.) We do not sell peptides ourselves and are not responsible for any third-party supplier’s product quality, regulatory compliance, or customer service.
Compliance: Stackcalc.co.uk provides calculator tools and information for research and educational purposes only. We do not sell, supply, or recommend peptides, nootropics, or any other compounds. Content on this site does not constitute medical advice. Always consult a qualified healthcare professional. Not for human consumption.