Retatrutide results show weight loss alongside health problems

A group's weight loss doesn't predict your own loss

A looser waistband tells you something about your own weight. Study averages describe other people, receiving medicine with doctors watching them. Phase 2, early testing of benefit and harm, found average retatrutide weight loss up to 24.2% over 48 weeks ^[1]. That exceeded older medicines copying these hormones, without promising the same loss for you.

Researchers assigned treatments by chance to make the comparison fair. Even a fair test can't make your body match the group's average. The studies haven't settled retatrutide's lasting benefits or risks, and findings from people watched by study doctors don't establish safe use of a product whose contents haven't been checked.

Phase 2 found weight loss with stomach trouble (Jastreboff 2023 [1])

Retatrutide's Phase 2 endpoints describe outcomes in a selected study population ^[1]; peptide care through Promise Peptides (mypromise.com) requires a prescription based on a licensed clinician's assessment. A study average cannot establish whether a treatment is suitable for an individual.

Trial design: 48-week randomized, double-blind, placebo-controlled Phase 2 trial. 338 adults with obesity (BMI ≥30) or overweight (BMI 27-<30) with at least one weight-related comorbidity; 51.8% male. Doses: 1, 4, 8, or 12 mg subcutaneous once weekly.

Body-weight change (48 weeks):

• 12 mg: mean -24.2% (vs -2.1% placebo)
• 8 mg: mean -22.8%
• 4 mg: mean -17.3%
• 1 mg: mean -8.7%

Proportion achieving ≥5% weight loss at 48 weeks:

• 12 mg: 100%
• Placebo: 26%

GI adverse events: Dose-related nausea, diarrhea, vomiting, and constipation; nausea in up to 45% at the highest dose; mostly mild-to-moderate.

Discontinuation: 18% at 12 mg (primarily GI tolerability); 2-5% placebo.

Heart rate: Dose-dependent increase peaking at approximately 24 weeks; mean increase approximately 5-7 bpm at highest doses.

Injection-site reactions: Approximately 8% of participants.

Phase 2 found better sugar tests in type 2 diabetes (Rosenstock 2023 [2])

This early Phase 2 test followed 281 adults with type 2 diabetes in a 36-week test. Weekly amounts ranged from 0.5-12 mg, with other people given placebo, shots without the drug, or another treatment. Neither patients nor staff knew who received which treatment.

At 24 weeks, sugar fell at 12 mg while placebo barely changed sugar. Sugar also fell at 3 mg and with increases written as 4/8/12 mg: four, then eight, then twelve milligrams. Those sugar tests don't predict your own response.

At 36 weeks, weight fell 16.94% at 12 mg, compared with 3.00% with placebo. Weight also fell at 2 mg and in the 4/8/12 mg group with those gradual increases. Stomach trouble affected 35%, without deaths or dangerously low sugar; people on insulin, the hormone helping cells take in sugar, needed less under doctors' care.

Phase 1b checked a small group with diabetes (Urva 2022 [4])

Phase 1b, an early repeated-shot test, followed 72 adults with type 2 diabetes for 12 weeks. Groups kept 0.5, 1.5 or 3 mg weekly. Others received 3/6 mg, meaning three then six milligrams, or 3, then 6, then 9, then 12 mg.

Half the retatrutide remained in blood after 6 days. The highest group lost more weight over 12 weeks than placebo, shots without drug. The 90% confidence range estimated 6.75 to 11.16 kilograms of extra loss; nine of ten ranges made for similar studies would cover the real average.

Blood sugar before eating fell at 3 mg. New troubles affected 63% of participants, mainly stomach and bowel problems. Nobody died; risks were judged acceptable.

A small liver study found less fat (Sanyal 2024 [5])

Only 98 people with high weight and fatty liver took part. They didn't have type 2 diabetes; liver scans showed at least 10% fat. Weekly groups received 1, 4, 8 or 12 mg.

At 24 weeks, the 12 mg group lost 82.4% of its original liver fat. Placebo changed little; fat also fell at 8, 4 and 1 mg. Most of the original fat was gone, but some remained.

Normal meant below 5% liver fat; 86% of people reached that at 12 mg by 24 weeks. The fat loss lasted through 48 weeks. The 12 mg group had then lost 86.0% of its original liver fat.

2024–2025 reports found muscle loss and better kidney readings

Scans found muscle and fat loss. Coskun's smaller 2025 X-ray study examined adults with type 2 diabetes ^[12]. Fat and muscle decreased, along with other tissue. Your strength can't be judged from weight alone.

Kidneys let less protein escape into urine. A 2025 report found about 37% less leakage at 12 mg in diabetes, compared with placebo ^[13]. Protein, a substance used to build tissue and carry other substances, normally stays in blood; damaged kidneys can let some pass into urine. In obesity, leakage fell 28-31% at 8-12 mg, and blood tests suggested better filtering, without proving lasting protection.

Tests linked burning fat with weight loss. Pearson's 2026 calculations concerned people without diabetes ^[14]. Tests suggested more fat burning contributed to weight loss, alongside lower blood fats and better use of insulin, the hormone helping cells take in sugar. The findings can't predict your weight loss from fat burning alone.

Proteins that handle blood fats also decreased. Wen's 2025 work found drops at 8-12 mg ^[15]. The proteins help control how fats move through blood. Less harmful cholesterol was encouraging, but didn't prove less future illness.

Retatrutide vs tirzepatide covers the early Phase 2 findings and larger Phase 3 comparison. Studies conducted separately don't fairly rank the medicines. Retatrutide effects explains unproved claims from people trying research products.