What each study in people found
Retatrutide Research: Phase 2 Results and Questions
Earlier studies found weight, sugar, and liver changes. Phase 3 must still answer the longer safety questions.
Studies in people found four main changes
Studies in people measured blood sugar, body weight, liver fat, and time in blood. Retatrutide isn’t an approved drug.
The TRIUMPH Phase 3 work is under way. Phase 1 and Phase 2 came first. Reviews have compared their findings.
Retatrutide acts like three hormones. Older drugs act like one or two. The three actions come from one shot.
In Phase 2, average weight fell about 24% by 48 weeks [1]. Long-term blood sugar fell 2.02% by 24 weeks [2]. Liver fat fell 82.4% by 24 weeks [5].
An early study found half was gone in about 6 days [4]. Heart, kidney, diabetes, and obesity studies continue. As of 2026, approval hadn’t come.
A blood test showed the sugar change. Each study stage asks different questions. None can tell your own result.
Your body isn’t an average. A study can’t know your response.
Your doctor has your health history. Group figures don’t.
Phase 1 checked early safety. Phase 2 measured health changes. Phase 3 now follows larger groups for longer.
Your doctor can hear your concerns.
Three hormone actions may explain the weight loss
Your body releases hormones after you eat. Retatrutide acts like three of them. Each hormone has a different job.
One action may curb hunger for you. Your gut sends this hormone after food. The hormone also slows your stomach.
It helps your pancreas release insulin. The help rises with your blood sugar. Approved weight drugs already copy this hormone.
Another action helps after meals. This gut hormone also helps release insulin. It may change how fat holds fuel.
In 2024, lab pictures showed retatrutide attached where that hormone normally works [3]. The drug also holds onto a blood protein and lasts longer. Pictures can’t show your weight change.
The last action starts with a pancreas hormone. It may lift blood sugar. The same hormone tells your liver to free stored fuel.
The first two actions may balance that sugar rise. Together, they may burn more fuel. Larger studies must test that idea.
The three actions start work inside cells. Researchers think the mix may deepen weight loss [6]. You don’t need the lab codes.
In 2025, a review compared older and newer drugs [8]. It found retatrutide worked in a different way. Long-term safety wasn’t clear.
Tests in cells found one action stronger than the other two. A fatty acid, which is a kind of fat, helps the drug hold onto blood protein [3]. This explains why it lasts, not what you’d lose.
The third action may free stored fuel. The other two may hold down the blood sugar increase. Reviews can’t prove that balance in you.
Cell tests can’t predict your change. They won’t settle your safety.
No chart knows your health. Your doctor must judge it with you.
Doctors call the first gut hormone GLP-1. It may curb hunger and help insulin. It may also slow your stomach. Older drugs copy GLP-1 alone. Newer drugs may add another hormone action to GLP-1. Retatrutide adds two actions to GLP-1. GLP-1 remains one part of the drug.
Only you have your full history.
Phase 2 measured weight, sugar, and liver fat
In 2023, the weight study followed 338 adults.
People got 1 mg, 4 mg, 8 mg, or 12 mg. The study ran 48 weeks.
At 12 mg, average weight fell 24.2%. The placebo group lost 2.1% [1].
In 2023, the diabetes study followed 281 adults. Study doctors raised amounts step by step to 12 mg.
At 24 weeks, a long-term blood sugar test fell 2.02%. The placebo change was 0.01%. At 36 weeks, weight fell 16.94%.
The placebo group lost 3.00%. Stomach trouble affected 35% [2]. Nobody suffered a severe blood sugar low. The study recorded no deaths.
In 2024, the liver study followed 98 people. Each had at least 10% liver fat, and none lived with type 2 diabetes.
At 12 mg, liver fat fell 82.4% by 24 weeks. The placebo change was 0.3%. By then, 86% reached normal liver fat.
Normal meant less than 5%. The drop held at 48 weeks [5]. You might not match these group averages.
In 2022, the first human study followed 72 adults. Each had type 2 diabetes. Study doctors raised the amounts more than once.
After about 6 days, half the drug was gone from blood. The highest group lost 8.96 kg more than the placebo group. That took 12 weeks.
Side effects affected 63%, mostly the stomach and bowel [4].
Together, these studies found all three health changes. They can’t promise your result.
The diabetes study began as low as 0.5 mg. A blood test checked average sugar over several months. Doctors repeated the test later.
At 12 mg, doctors checked that blood test at week 24. That is the same as 24 weeks. The liver study later found an 86.0% fall. Both were Phase 2 studies.
The small early study gave a wide range around weight loss. The true group average could sit anywhere within it.
Doctors compared weight with height. A result of 30 meant obesity. Some entered at 27 with another illness. The paper gave a 90% range around its estimate. Another Phase 2 check followed.
You can bring these facts along.
Phase 3 is checking hearts, kidneys, and weight
The Phase 3 studies are called TRIUMPH. They follow several groups:
- TRIUMPH-1 and TRIUMPH-2: People with obesity, with or without type 2 diabetes.
- TRIUMPH-3: People with obesity and known heart disease.
- A heart study: It counts major heart harm.
- A kidney study: It follows people with long-term kidney disease.
- Another kidney study: It measures changes in blood and the body.
- One more study: It checks sleep apnea and knee arthritis.
- A direct comparison: It compares retatrutide with tirzepatide.
In 2025, one review covered 53 Phase 2 and 3 weight studies. Retatrutide was one of 14 drugs in active Phase 3 work [11]. Those reviews couldn’t settle the long-term questions for you.
Another 2025 review looked at stomach trouble. It found slower rises in the amount may help [12]. Phase 3 studies use that lesson.
In 2026, a broad review covered all Phase 2 results. It reported blood sugar drops up to 2.16%. Weight loss reached 26.56% [15].
Heart and kidney results are still missing. You can’t judge the full balance yet.
TRIUMPH-1 also includes people living with obesity. Public study listings show where the studies take place.
The broad review also used a long-term blood sugar test. A study listing isn’t a result. It can’t answer your health questions.
Doctors need your own health facts. They won’t rely on one average.
A weight-to-height result of 30 also appears in one study’s rules.
You’ll still need care built around your needs.
Retatrutide hasn’t proved better than tirzepatide
Tirzepatide copies two hormone actions. The FDA approved it for type 2 diabetes and obesity. Retatrutide adds a third action.
In Phase 2, 12 mg of retatrutide led to 24.2% average loss. That study lasted 48 weeks. Tirzepatide’s Phase 3 study used 15 mg for 72 weeks.
The tirzepatide study found about 22.5% average loss. It followed different people for another length of time. You can’t fairly rank the drugs.
A TRIUMPH Phase 3 study compares them directly. In 2025, a review called retatrutide’s weight change large. It also found stomach trouble and faster pulse [6].
Tirzepatide is approved. Retatrutide isn’t. More questions remain about retatrutide.
The Retatrutide references page lists every source.
Each drug has its own study. The direct TRIUMPH study may give a fairer answer. Current figures can’t pick your care.
One report can’t define your result. You’ll need to share your full history with your doctor.
Phase 1 studies came before both comparisons. A Phase 1 result can’t rank the drugs.
You’ll need a fair comparison.
Retatrutide studies found stomach trouble and faster pulse
Phase 2 studies found several main side effects.
Stomach and bowel trouble came first. People had nausea, vomiting, diarrhea, and constipation. The trouble grew as the amount rose.
At the highest level, up to 45% had nausea. At 12 mg, 18% left the study [1]. A 2023 study found slower stomach emptying [9].
Resting pulse rose. The rise peaked near week 24. At the highest amounts, it reached 5–7 beats each minute [1].
The third hormone action may cause this change. A heart study is still checking the risk. We don’t have a long-term answer.
Some people had skin trouble where the needle entered. About 8% had a mild local reaction [1]. The study didn’t find a grave pattern for you.
People shed muscle plus other tissue while losing fat. A later study confirmed that loss [14].
In 2026, a safety review found burning or tingling skin. It saw this across similar drugs [13]. The review didn’t prove retatrutide alone caused that feeling in you.
The studies found skin trouble, muscle loss, and stomach trouble. They can’t show your own risk.
Study results aren’t your forecast. They can’t make your choice.
Phase 2 found the stomach trouble. Another Phase 2 study measured muscle loss.
Your strength is part of your health.