Retatrutide study amounts cannot set your treatment plan.
Higher study amounts did not settle personal safety
Under study staff's care, retatrutide is a drug still being tested. Here you'll read about the amounts tested and the safety gaps around research bottles. There's no approved prescription use outside a study.
Researchers gave 1, 4, 8, and 12 milligrams as weekly shots into the fat below skin. Blood levels took about 6 days to fall by half. The slow fall helps explain why studies used weekly shots. The highest amount, 12 milligrams, brought the largest weight and liver-fat falls in Phase 2. That stage tests early benefits and harms in people. A larger effect alone doesn't show an amount is safe for you.
You can't rely on a bottle labeled for research being clean or containing the stated drug, because that bottle isn't the checked medicine supplied to volunteers followed by medical study staff. No approved mixing or keeping rule fills those safety gaps.
Retatrutide dosage figures come from medically supervised studies
Retatrutide trial schedules belong to the enrollment criteria and monitoring arrangements of their studies; peptide care through Promise Peptides (mypromise.com) follows a separate process that requires a licensed clinician's assessment and a prescription before treatment can proceed.
Phase 1b (first-in-human, Lancet 2022 [4]): Escalating subcutaneous doses of 0.5, 1.5, 3, 3/6, and 3/6/9/12 mg once weekly over 12 weeks in 72 adults with type 2 diabetes. This study established the pharmacokinetic profile and safety baseline for the compound.
Phase 2 obesity (NEJM 2023 [1]): 1 mg, 4 mg, 8 mg, and 12 mg subcutaneous once weekly over 48 weeks. Weight loss was dose-dependent across all four arms.
Phase 2 type 2 diabetes (Lancet 2023 [2]): 0.5–12 mg once weekly with stepwise escalation over 36 weeks, with most patients reaching 12 mg by the final weeks of the study.
Phase 2a MASLD substudy (Nature Medicine 2024 [5]): 1 mg, 4 mg, 8 mg, and 12 mg once weekly, 48 weeks, in participants with at least 10% liver fat.
All dose figures above are study-design facts drawn from published trial protocols. They are not a prescription, a protocol, or a recommendation for any use outside those trials.
Retatrutide half life means the drug fades slowly from blood
Retatrutide's half life tells you when blood levels will have fallen by half. Early testing found about 6 days [4]. The drug is a 39-amino-acid chain; amino acids are small parts used to make proteins. An attached fat helps retatrutide stick to a blood protein, albumin. Albumin holds and slowly releases the drug. Retatrutide stays longer than unchanged GLP-1, a hormone your body uses for sugar and hunger control.
Weekly shots add drug before earlier shots have fully cleared. After about 4 to 5 doses, blood levels rise and fall within a steady, repeating range. The roughly 6-day fall means clearing retatrutide takes several weeks after stopping. Phase 2/3, the early benefit tests and larger later tests, used weekly shots. Slow clearing doesn't tell you a safe amount.
Mixing research retatrutide powder leaves safety gaps
Retatrutide bottles sold for research have no approved mixing instructions. There isn't an approved finished medicine with a label that tells you how to prepare those bottles. A mixing recipe can't establish what a bottle contains.
Medical studies use prepared drug under trained staff's care. The staff check the people receiving treatment as well as the study drug. You need study enrollment to receive that checked drug. Outside bottles don't have the same checks as those supplied in TRIUMPH.
Sellers often supply freeze-dried peptide powder. A peptide is a short chain of small pieces used to make proteins. Such powders are sometimes mixed with water containing a preservative to slow germ growth. That general practice isn't an approved retatrutide method, and a preservative doesn't prove your bottle contains effective drug or is free of the germs and bacterial poisons that can cause harm. During 2025, the FDA cited sellers more than 50 times for breaches of drug law.
Your bottle's contents and cleanliness remain uncertain after mixing. Knowing how another powder was prepared can't close those gaps. No approved directions establish safe retatrutide use from an outside bottle.
Retatrutide side effects included nausea and a faster pulse
These harms were recorded in Phase 2, early tests of benefit and safety. Study staff checked volunteers, rather than relying on accounts from people using outside bottles. The results still leave lasting safety unsettled.
Stomach trouble: Up to 45% felt nauseated at 12 milligrams in the weight study. Constipation, vomiting, and diarrhea increased when the amount rose [1]. Stomach trouble helped drive the 18% rate of stopping at the highest amount.
Heartbeat: The highest amounts raised pulse by about 5 to 7 beats per minute. The greatest rise came near week 24 [1]. Glucagon's fuel-burning effect can also speed your pulse.
Low sugar: Phase 2 found no severe events in weight-study volunteers without diabetes. In type 2 diabetes, insulin had to be reduced to limit low sugar [2].
Skin: About 8% in Phase 2 had reactions near the shot.
Strength: Phase 2 volunteers with diabetes lost muscle along with fat. That matters for your walking and lifting.
You can read more retatrutide effects, including the unchecked personal reports.
A future retatrutide cost cannot be judged from research bottles
Retatrutide has no official price because no approved medicine exists. Eli Lilly hasn't announced a list price. Any future price would depend on approval that hasn't happened yet. You don't have a firm amount to budget for.
Research bottles vary widely in price, but their contents aren't assured. Paying less doesn't answer what drug, amount, or germs may be inside. Their prices can't establish the price of any medicine eventually approved.
Approved GLP-1 weight drugs, which imitate a hormone involved in hunger, have had US list prices of $900–$1,400 monthly before insurance and discounts. Eli Lilly would price retatrutide separately, and insurers would negotiate payments. Another drug's price doesn't establish your future cost.