Abstract: The article is about long term (90 days) sugar level (Glycated Hemoglobin (HbA1c)), your blood, and a peptide; Retatrutide. Inside our body, we have millions of tiny red blood cells zooming around like little delivery trucks, carrying oxygen everywhere you need it. Each one of these trucks has a special part called hemoglobin. Now, when someone eats a lot of sugary food, or their body has trouble handling sugar, extra sugar floats around in the blood for a long time.
And here’s the tricky part: that sugar starts sticking to the hemoglobin, kind of like honey sticking to your fingers when you don’t wash your hands. Scientists call this ‘glycation,’ but you can just think of it as ‘sugar getting stuck.’ We can actually measure how much sugar is stuck on these blood cells, and we call that number HbA1c.
If too much sugar stays stuck for too long, it doesn’t just stay in the blood, it starts gumming up important parts of the body too, like the liver, which is supposed to stay clean and healthy, and the kidneys, which act like filters cleaning your blood every single day. When sugar sticks to those parts too much, they get tired and don’t work as well anymore. That’s the problem! Now here’s the exciting part, scientists like me have been working on new medicines that help the body handle sugar better, so it doesn’t stay stuck around for so long.
One of these new medicines is called retatrutide. Think of it like a helper that tells the body, ‘Hey, let’s use this sugar for energy instead of letting it float around and get stuck everywhere!’ In science tests, this medicine has helped people’s sugar-stuck number go down, helped clean up extra fat sitting in the liver, and even helped protect the kidneys. It’s still being tested to make sure it’s totally safe before doctors can give it to patients, but it shows us how exciting science can be, when we understand a problem really well, we can invent smart solutions to help people stay healthy!
Glycated Hemoglobin (HbA1c), Retatrutide, The liver and the Kidneys : Where All They Are Connected and How?
If you have type 2 diabetes, or you are at risk of it, you have probably heard your doctor mention a number called Glycated Hemoglobin (HbA1c). This one number tells a doctor how your blood sugar has behaved over the last two to three months. It is one of the most trusted tools in diabetes care anywhere in the world.
But Glycated Hemoglobin (HbA1c) is not just a diabetes number. It is closely tied to two organs that quietly suffer when blood sugar stays high for too long: the liver and the kidneys. When glucose molecules stick to hemoglobin inside red blood cells, they also stick to proteins inside the liver and the tiny filtering units of the kidneys. Over years, this sticking process, called glycation, damages tissue, stiffens blood vessels, and speeds up conditions such as liver steatosis (fatty liver) and diabetic kidney disease.
This is where a new medicine called retatrutide enters the picture. Retatrutide is a research peptide from Eli Lilly that acts on three hormone receptors at once. In clinical trials, it has lowered Glycated Hemoglobin (HbA1c) by close to 2 percentage points, shrunk liver fat by more than 80%, and shown early signs of protecting kidney function in people with obesity and type 2 diabetes.
In this article, we will explain what Glycated Hemoglobin (HbA1c) is, why high levels damage the body, and why “lower is better” is not always as simple as it sounds. Then we will look closely at retatrutide itself: what it is, how it was developed, how it works inside the body, and what the large TRIUMPH clinical trial program has shown so far about its effects on Glycated Hemoglobin (HbA1c), liver fat, and kidney health.
Key Takeaways
- Glycated Hemoglobin (HbA1c) measures the average amount of glucose attached to red blood cells over roughly 90 days, giving a long-term picture of blood glucose levels.
- High Glycated Hemoglobin (HbA1c) is linked to diabetes mellitus complications, including liver steatosis, diabetic kidney disease, nerve damage, and atherosclerotic plaque buildup in blood vessels.
- Very low Glycated Hemoglobin (HbA1c) is not automatically better; aggressive lowering can raise the risk of hypoglycemia, especially in older adults or people with certain blood conditions.
- Retatrutide is a first-in-class triple hormone receptor agonist that activates GIP, GLP-1, and glucagon receptors at the same time.
- In Phase 2 and Phase 3 trials, retatrutide lowered Glycated Hemoglobin (HbA1c) by up to 2.0 percentage points and cut liver fat by up to roughly 82% to 86% in people with fatty liver disease.
- Early kidney data show reductions in urine albumin-to-creatinine ratio (UACR), a marker of diabetic kidney disease, alongside modest gains in estimated kidney filtration.
- Retatrutide has not yet been approved by the FDA. Multiple Phase 3 TRIUMPH trials are still reporting results through 2026, and a formal application is expected later in 2026 or in 2027.
- The drug should never be confused with an approved treatment; it remains investigational, and dedicated outcome trials for kidney and heart disease are still ongoing.
What Is Glycated Hemoglobin (HbA1c)?
Hemoglobin is the protein inside red blood cells that carries oxygen around your body. When sugar (glucose) circulates in your blood, some of it naturally attaches itself to hemoglobin, without any enzyme controlling the process. This is called glycation, and the resulting protein is called glycosylated hemoglobin, or more precisely, Glycated Hemoglobin (HbA1c).
The “A1c” part refers to a specific fraction of hemoglobin. Glucose usually binds at the N-end of the beta chain of the hemoglobin molecule, forming an unstable compound called a Schiff base. Over several hours, this Schiff base rearranges into a much more stable structure called a ketoamine. Once that stable bond forms, it does not come off. It stays attached for the entire lifespan of the red blood cells carrying it, which is around 120 days.
Because red blood cells are constantly being made and replaced, the Glycated Hemoglobin (HbA1c) value at any given moment reflects an average of blood glucose levels over the past two to three months, weighted more heavily toward the most recent 30 days. This is very different from a finger-prick glucose test, which only shows your sugar level at that exact second.
Labs measure Glycated Hemoglobin (HbA1c) using several methods, but one of the most common and accurate is cation exchange chromatography. This technique separates hemoglobin types based on their electrical charge, allowing the lab to isolate and quantify the glycated fraction precisely. Other methods include immunoassay and boronate affinity chromatography, but cation exchange chromatography remains a gold-standard reference technique in many laboratories.
Glycated Hemoglobin (HbA1c) results can be reported in two different units. In the United States, it is usually shown as a percentage, sometimes called the DCCT %, named after the Diabetes Control and Complications Trial that first validated this measurement approach. Internationally, many labs report it in mmol/mol, a unit adopted through standardization efforts led by the International Federation of Clinical Chemistry. A Glycated Hemoglobin (HbA1c) of 7.0% is roughly equal to 53 mmol/mol.
What Does a High Glycated Hemoglobin (HbA1c) Level Mean?
A high Glycated Hemoglobin (HbA1c) level means that, on average, too much glucose has been circulating in your bloodstream for weeks or months. According to American Diabetes Association guidelines, a Glycated Hemoglobin (HbA1c) of 6.5% or higher, confirmed on repeat testing, is one of the criteria used to diagnose diabetes mellitus. A value between 5.7% and 6.4% is classified as prediabetes, while anything below 5.7% is considered within the normal range for someone without diabetes.
For people already diagnosed with diabetes, ADA guidelines generally recommend a treatment target of below 7.0% for most adults, though this target is individualized. Younger, healthier patients may aim lower, while older adults with multiple health conditions may have a more relaxed goal to avoid other risks, which we will explain shortly.
Why does a high number matter so much? Because it is not just a measurement of blood glucose levels, it is a working record of ongoing tissue exposure to sugar. The landmark UKPDS (UK Prospective Diabetes Study), one of the longest and largest diabetes trials ever conducted, showed that every 1 percentage point reduction in Glycated Hemoglobin (HbA1c) was associated with meaningful drops in the risk of diabetes-related complications, including a reduction in deaths related to diabetes, heart attacks, and microvascular problems affecting the eyes, nerves, and kidneys.
A chronically high Glycated Hemoglobin (HbA1c) level signals to your care team that your current diabetes mellitus management plan, whether it is diet, exercise, oral medication, or insulin, is not adequately controlling glycemic control. Left unaddressed, it sets off a chain of biological damage that touches nearly every organ system, especially the liver, kidneys, eyes, nerves, and blood vessels.
The Lower the Glycated Hemoglobin (HbA1c) Level, Is It That Simple as the Lower the Better?
It is tempting to think that pushing Glycated Hemoglobin (HbA1c) as low as possible is always the safest choice. In reality, this is not that simple.
Several major clinical trials, including the ACCORD trial, tested whether extremely intensive glucose lowering (targeting a Glycated Hemoglobin (HbA1c) near 6.0%) improved outcomes compared with standard targets around 7% to 7.9%. Surprisingly, the intensive-control group in that trial had a higher rate of death, and the study was stopped early for safety reasons. Researchers believe this was linked, at least in part, to a higher frequency of severe hypoglycemia, dangerously low blood sugar episodes that can cause falls, confusion, seizures, and cardiac problems, especially in older adults.
There are also technical reasons why an unusually low or unusually high Glycated Hemoglobin (HbA1c) reading can be misleading rather than reassuring. Because the test depends on the lifespan and health of red blood cells, any condition that shortens or lengthens that lifespan will distort the result, even if actual blood glucose levels have not changed. For example:
- Glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency), a common inherited enzyme condition, can cause red blood cells to break down faster than normal. This shortens their circulating lifespan, giving less time for glucose to attach, which can falsely lower the Glycated Hemoglobin (HbA1c) reading even when true blood sugar is elevated.
- Sickle-cell disease and other hemoglobin variants can interfere with standard testing methods, sometimes producing an inaccurate Glycated Hemoglobin (HbA1c) result because the abnormal hemoglobin structure is not measured the same way as normal adult hemoglobin.
- Conditions such as anemia, recent blood transfusion, chronic kidney disease, and pregnancy can also shift red blood cell turnover and distort readings in either direction.
Because of these limitations, doctors do not rely on Glycated Hemoglobin (HbA1c) alone. They combine it with fasting glucose checks, continuous glucose monitoring data when available, and a full clinical picture of the patient. The goal is genuinely balanced glycemic control: low enough to prevent long-term organ damage, but not so aggressively low that it creates new, immediate dangers. This is precisely the kind of controlled, steady reduction that newer medicines, including retatrutide, appear to be designed around, gradual, sustained glucose lowering rather than sudden drastic swings.
Damage Mechanisms of Glycated Hemoglobin (HbA1c)
Understanding why elevated Glycated Hemoglobin (HbA1c) is dangerous requires looking past the number itself and into what sustained high glucose actually does to tissue at a cellular level.
1. Advanced glycation end-products (AGEs)
The same glycation process that creates Glycated Hemoglobin (HbA1c) inside red blood cells also happens to other long-lived proteins throughout the body, including collagen in blood vessel walls, proteins in the eye’s lens, and structural proteins in the kidney’s filtering units. Over time, these glycated proteins form permanent, cross-linked structures called advanced glycation end-products. AGEs stiffen tissue, trigger inflammation, and damage the normal function of cells they accumulate in.
2. Vascular injury and atherosclerotic plaque
High blood glucose levels damage the thin layer of cells lining blood vessels, called the endothelium. This damage exposes the subendothelium, the deeper tissue layer beneath the vessel lining, to circulating fats and inflammatory cells. Over years, this process contributes to the buildup of atherosclerotic plaque, fatty deposits that narrow arteries and raise the risk of heart attack and stroke. People with poorly controlled diabetes mellitus, and correspondingly high Glycated Hemoglobin (HbA1c), tend to develop atherosclerotic plaque earlier and more extensively than people with well-controlled glucose.
3. Liver fat accumulation (liver steatosis)
Chronically elevated blood glucose levels drive the liver to convert excess sugar into fat through a process called de novo lipogenesis. At the same time, insulin resistance, closely tied to high Glycated Hemoglobin (HbA1c), causes fat tissue to release more free fatty acids into the bloodstream, many of which end up stored in the liver. This combination is a central driver of metabolic dysfunction-associated steatotic liver disease, more commonly known as fatty liver disease or liver steatosis.
4. Kidney filtration damage
The kidneys contain millions of tiny filtering units called nephrons, each built around a cluster of blood vessels called a glomerulus. Persistently high glucose damages these delicate vessels through glycation of structural proteins, thickening of the basement membrane, and abnormal pressure changes within the filtering unit. This progressive injury is the root cause of diabetic kidney disease, one of the leading causes of kidney failure worldwide. Early signs include a rising urine albumin-to-creatinine ratio (UACR), showing that protein is leaking into the urine because the filter is no longer working properly.
5. Oxidative stress and inflammation
High glucose promotes the production of reactive oxygen species inside cells, a state called oxidative stress. Combined with the low-grade, chronic inflammation associated with obesity and insulin resistance, this creates a hostile internal environment that accelerates aging in blood vessels, liver tissue, and kidney tissue simultaneously.
Put together, these mechanisms explain why a single lab value, Glycated Hemoglobin (HbA1c), correlates so strongly with liver and kidney outcomes. It is not the number itself causing harm; it is the sustained high blood glucose levels the number reflects, working through glycation, inflammation, and vascular injury, that damage tissue over years.
How Retatrutide Helps Control the Balanced Level?
Given everything above, an ideal diabetes and metabolic disease treatment would do three things at once: lower Glycated Hemoglobin (HbA1c) steadily without causing dangerous blood sugar crashes, reduce the fat accumulating in the liver, and protect the kidneys from ongoing glycation-related damage. Retatrutide appears to check all three boxes, at least based on the clinical data gathered so far.
Retatrutide lowers Glycated Hemoglobin (HbA1c) primarily by improving insulin secretion in a glucose-dependent way (meaning it stimulates insulin mainly when blood sugar is already high, reducing the chance of a crash), slowing stomach emptying so glucose enters the bloodstream more gradually, and reducing appetite, which leads to weight loss and improved insulin sensitivity throughout the body.
For the liver, retatrutide’s glucagon receptor activity appears to play a unique role. Glucagon receptor signaling promotes the liver’s ability to burn stored fat for energy and suppresses the liver’s own fat production process. Combined with substantial weight loss, this produces some of the largest liver fat reductions ever reported for a pharmaceutical agent in a controlled clinical trial.
For the kidneys, the benefit appears to be a combination of indirect and possibly direct effects: less glucose-driven glycation damage, lower blood pressure, reduced excess weight pressing on the kidneys, and improved fat and cholesterol profiles, all of which reduce the physiological burden placed on the nephrons. Researchers are still working out exactly how much of the kidney benefit comes from these indirect pathways versus any direct action on kidney tissue itself.
What Is Retatrutide?
Retatrutide, known by its research code LY3437943, is an investigational, once-weekly injectable medicine developed by Eli Lilly and Company. It belongs to a class of drugs called triple hormone receptor agonists. Unlike single-target diabetes medicines, retatrutide is engineered to activate three separate hormone receptors simultaneously:
- GIP receptor (glucose-dependent insulinotropic polypeptide)
- GLP-1 receptor (glucagon-like peptide-1)
- Glucagon receptor
This triple-action design places retatrutide in the same broad drug family as tirzepatide (marketed as Mounjaro and Zepbound), which activates GIP and GLP-1 receptors, but retatrutide goes a step further by adding glucagon receptor activity on top.
Retatrutide is currently being studied for obesity, type 2 diabetes, obstructive sleep apnea, knee osteoarthritis, metabolic dysfunction-associated steatotic liver disease, chronic kidney disease, and cardiovascular outcomes. As of mid-2026, it remains an investigational drug and is not approved for prescription use anywhere.
How Retatrutide Was Developed?
Retatrutide grew out of decades of scientific work on gut hormones and their role in regulating appetite and blood sugar. Researchers had already learned, through the development of GLP-1 receptor agonists like exenatide and semaglutide, that activating the GLP-1 receptor could meaningfully improve glycemic control and support weight loss.
The next major step came with tirzepatide, which combined GIP and GLP-1 receptor activity into a single molecule and demonstrated that hitting two receptors together could outperform either target alone. Building on that success, Eli Lilly’s research team designed retatrutide as a single peptide capable of engaging a third receptor, glucagon, which had historically been avoided in diabetes drug design because glucagon alone raises blood sugar. However, when combined with strong GIP and GLP-1 activity, the glucagon component instead appears to boost energy expenditure and liver fat metabolism without undermining overall glycemic control.
Retatrutide’s clinical development began with early Phase 1 studies. The first was a single ascending dose study conducted in Singapore involving 47 healthy volunteers, designed to establish basic safety and confirm that the drug’s pharmacokinetics supported convenient once-weekly dosing. This was followed by a Phase 1b multiple-ascending dose study in people with type 2 diabetes, published in The Lancet in 2022, which showed encouraging early reductions in both blood glucose levels and body weight.
Those early results supported moving into larger Phase 2 studies, and eventually into the current Phase 3 program, called TRIUMPH, which is the focus of the next section.
How Retatrutide Works?
To understand how retatrutide affects Glycated Hemoglobin (HbA1c), liver steatosis, and diabetic kidney disease, it helps to look at what each of its three hormone targets does on its own, and then how they work together.
GIP receptor activation enhances insulin release from the pancreas after meals and appears to play a role in fat tissue metabolism, potentially reducing fat storage and improving how the body processes triglycerides.
GLP-1 receptor activation is well studied. It stimulates insulin release in a glucose-dependent manner, suppresses glucagon release from the pancreas when blood sugar is high, slows gastric emptying (which flattens after-meal glucose spikes), and acts on appetite centers in the brain to reduce hunger and food intake.
Glucagon receptor activation is the feature that sets retatrutide apart from earlier drugs. In the liver, glucagon receptor signaling increases fat oxidation (burning stored fat for energy) and reduces new fat production. It also raises resting energy expenditure, meaning the body burns more calories even at rest. On its own, glucagon would raise blood glucose levels by triggering the liver to release stored sugar. But because retatrutide simultaneously and powerfully activates the GIP and GLP-1 receptors, the insulin-boosting and appetite-suppressing effects offset this, resulting in an overall pattern of substantial weight loss and improved Glycated Hemoglobin (HbA1c), not worsened blood sugar.
The net clinical effect of this triple mechanism is a medicine that reduces appetite and caloric intake, improves how the pancreas releases insulin, slows the digestion of glucose-containing food, and directly encourages the liver to burn rather than store fat. All four of these effects work together to lower Glycated Hemoglobin (HbA1c), shrink liver fat, and reduce the metabolic strain placed on the kidneys.
The TRIUMPH Trials of Retatrutide
Brief Overview of All Phases
Retatrutide’s clinical testing follows the typical drug development path, moving from small, careful early studies to large, multi-year trials involving thousands of participants.
Phase 1 consisted of the single ascending dose study in healthy volunteers and the multiple ascending dose study in people with type 2 diabetes, both designed to confirm basic safety, tolerability, and appropriate dosing.
Phase 2 was a landmark 48-week obesity trial that produced striking early results, with participants on the highest doses losing roughly 22.8% to 24.2% of their body weight, alongside a dedicated liver fat substudy and a separate Phase 2 trial in people with type 2 diabetes that showed Glycated Hemoglobin (HbA1c) reductions of up to about 2.0 percentage points.
Phase 3, called the TRIUMPH program (TRIple-hormone receptor AgonIst for Metabolic diseases), is the current, ongoing stage. It is actually a family of related trials, each targeting a different patient population or health condition:
- TRIUMPH-1: adults with obesity or overweight, with at least one weight-related health problem, without diabetes. This trial focuses on weight loss as its primary measure.
- TRIUMPH-2: adults with obesity and type 2 diabetes, with co-primary endpoints of body weight change and Glycated Hemoglobin (HbA1c) change.
- TRIUMPH-3: focused on cardiovascular safety and outcomes in higher-risk patients.
- TRIUMPH-4: adults with obesity or overweight and knee osteoarthritis, the first Phase 3 trial in the program to report results.
- TRIUMPH-Outcomes: a large, long-term cardiovascular and kidney outcomes trial in adults with obesity and either established cardiovascular disease or chronic kidney disease.
- TRANSCEND-T2D-1: part of a separate, dedicated three-trial program specifically evaluating retatrutide in type 2 diabetes, distinct from the main TRIUMPH obesity trials.
- TRANSCEND-CKD: a mechanistic Phase 2b trial designed specifically to study retatrutide’s effects on kidney function and structure using precise filtration-rate measurement.
Additional Phase 3 studies are also evaluating retatrutide for metabolic dysfunction-associated steatotic liver disease (MASLD), obstructive sleep apnea, and chronic low back pain, reflecting how broadly this single molecule’s effects reach across different body systems.
Which Phase Discussed Retatrutide and Glycated Hemoglobin (HbA1c)?
Glycated Hemoglobin (HbA1c) has been a tracked outcome from the very first diabetes-focused human trial onward, but the most detailed and statistically powered data come from two trials in particular.
The Phase 2 type 2 diabetes trial enrolled adults aged 18 to 75 with an HbA1c between 7.0% and 10.5% and a BMI between 25 and 50. This randomized, double-blind, placebo- and active-comparator-controlled study compared multiple retatrutide doses against both placebo and dulaglutide, an already approved GLP-1 receptor agonist, giving early evidence of how retatrutide’s Glycated Hemoglobin (HbA1c) lowering effect compared with existing treatment.
The Phase 3 TRANSCEND-T2D-1 trial, part of the newer, dedicated diabetes program, is where Glycated Hemoglobin (HbA1c) was formally studied as the primary endpoint at the Phase 3 level. This 40-week, placebo-controlled trial enrolled 537 adults with type 2 diabetes and was designed specifically to determine whether retatrutide could produce a statistically superior reduction in Glycated Hemoglobin (HbA1c) compared with placebo. Its results were presented at the American Diabetes Association’s 86th Scientific Sessions and published simultaneously in The Lancet.
What Were the Outcomes of TRIUMPH program?
The Glycated Hemoglobin (HbA1c) results across retatrutide’s clinical program have been consistently strong:
Phase 2 diabetes trial
Mean Glycated Hemoglobin (HbA1c) reduction of up to approximately 2.02 percentage points at the highest doses, with no reports of severe hypoglycemia. Reductions were significantly greater than placebo across nearly all dose groups and, at the higher doses, significantly greater than the active comparator dulaglutide.
Phase 3 TRANSCEND-T2D-1 trial
At 40 weeks, participants achieved mean Glycated Hemoglobin (HbA1c) reductions of 1.7, 2.0, and 1.9 percentage points with the 4 mg, 9 mg, and 12 mg doses respectively, compared with a 0.8 percentage point reduction with placebo. Up to roughly 90% of participants taking retatrutide achieved a Glycated Hemoglobin (HbA1c) below 7.0%, the treatment target recommended in ADA guidelines. Alongside this, participants on the highest dose lost an average of about 16.8% of their body weight over the same 40-week period, with no plateau in weight loss observed by the end of the study.
Liver fat (steatosis) results
In the pre-specified Phase 2 liver fat substudy, published by Sanyal and colleagues in Nature Medicine, participants with metabolic dysfunction-associated steatotic liver disease saw their liver fat content drop by a mean of 42.9% (1 mg dose), 57.0% (4 mg), 81.4% (8 mg), and 82.4% (12 mg) at 24 weeks, compared with essentially no change on placebo. At the two highest doses, more than 80% of participants achieved at least a 70% relative reduction in liver fat, and over 85% achieved full resolution of steatosis, defined as liver fat content below 5%. Some later reporting on extended follow-up describes reductions approaching 86%, among the largest liver fat reductions ever recorded for any pharmaceutical agent in a controlled trial.
Kidney (diabetic kidney disease) results
Post-hoc analyses of the Phase 2 obesity and type 2 diabetes trials found urine albumin-to-creatinine ratio (UACR) reductions of roughly 31.5% in the obesity population and around 37% in the type 2 diabetes population at the 12 mg dose, along with modest estimated kidney filtration (eGFR) improvements of about 8.5 mL/min/1.73m² in the obesity cohort. These are encouraging early signals rather than confirmed outcomes; researchers have been clear that this data requires confirmation in larger, longer, dedicated kidney trials. Two such trials are now underway: TRANSCEND-CKD, a mechanistic study using precise iohexol-clearance measured GFR to understand how retatrutide affects kidney filtration and structure, and TRIUMPH-Outcomes, a large, roughly five-year cardiovascular and kidney outcomes trial in people with obesity and established cardiovascular disease or chronic kidney disease.
Across all of these trials, the most common side effects have been mild-to-moderate gastrointestinal symptoms, along with a newly observed signal for urinary tract infections in some Phase 3 data. Discontinuation rates due to side effects rose somewhat with higher doses but generally remained modest.
Who Were the Scientists Behind This Retatrutide’s Clinical Trial Program?
Retatrutide’s clinical program has been led by well-recognized figures in endocrinology and metabolic disease research.
- Ania M. Jastreboff, MD, PhD, director of the Yale Obesity Research Center, has served as principal investigator on the flagship TRIUMPH-1 obesity trial and has presented and published extensively on retatrutide’s weight and metabolic effects.
- Julio Rosenstock, MD, Director of Velocity Clinical Research and Clinical Professor of Medicine at the University of Texas Southwestern, led the earlier Phase 2 diabetes trial and has been a long-standing leader in diabetes drug development research.
- Harpreet S. Bajaj, MD, MPH, an endocrinologist at LMC Diabetes & Endocrinology in Toronto, served as principal investigator on the TRANSCEND-T2D-1 trial.
- Arun Sanyal and colleagues led the dedicated liver fat substudy published in Nature Medicine, a group with a long track record in liver disease research.
The overall program is sponsored and coordinated by Eli Lilly and Company, with results reviewed and presented through peer-reviewed journals such as The Lancet and Nature Medicine, and at major professional meetings including the American Diabetes Association Scientific Sessions.
Why Is It Safe to Believe Them?
There are several reasons the retatrutide data can be reasonably trusted, while still being interpreted with appropriate caution.
First, the trials use rigorous, standard clinical research designs: randomized assignment, double-blind conditions (so neither participants nor most researchers know who received the real drug versus placebo), and, in several studies, an active comparator like dulaglutide for direct, real-world context.
Second, key results have gone through independent peer review before publication in respected medical journals such as The Lancet and Nature Medicine, meaning outside experts scrutinized the study methods and data before publication, rather than the results being announced through press releases alone.
Third, the trials have been presented at major independent medical conferences, such as the American Diabetes Association Scientific Sessions, where outside specialists in the field can review, question, and publicly comment on the findings.
Fourth, the principal investigators are established academic researchers, some with no direct financial ties to Eli Lilly, based at recognized institutions such as Yale University and the University of Texas Southwestern, adding a layer of independent scientific oversight to trial conduct and interpretation.
That said, it is worth being clear-eyed: Eli Lilly funds and sponsors this entire program, and topline results are often announced by the company itself before full peer-reviewed publication. Responsible readers should treat early press releases as preliminary and wait for full peer-reviewed data, and should remember that retatrutide remains investigational and unapproved.
Why Has the FDA Not Yet Approved Retatrutide?
As of mid-2026, retatrutide is not FDA approved and is not available by prescription anywhere. This is simply a reflection of where the drug currently sits in the standard, multi-year regulatory pathway, not a sign that anything has gone wrong.
Drug approval in the United States requires a completed, well-documented package of Phase 3 trial data across each intended use. Eli Lilly’s retatrutide program spans several separate patient populations and conditions: obesity, type 2 diabetes, knee osteoarthritis, obstructive sleep apnea, liver disease, and cardiovascular and kidney outcomes. Each of these areas needs its own supporting Phase 3 evidence before a New Drug Application (NDA) can be submitted to the FDA.
As of this writing, only a handful of these Phase 3 trials have reported topline results: TRIUMPH-4 in December 2025, TRIUMPH-1 in May 2026, and TRANSCEND-T2D-1 with topline data in March 2026 and full peer-reviewed publication in June 2026. Several additional Phase 3 readouts, including TRIUMPH-2, TRIUMPH-3, and the dedicated MASLD/liver disease trial, are expected to report through the remainder of 2026. Long-duration outcome trials like TRIUMPH-Outcomes and TRANSCEND-CKD, which are specifically designed to prove cardiovascular and kidney benefit over years rather than months, will take considerably longer to complete, since they are event-driven studies that require enough participants to experience real clinical outcomes before conclusions can be drawn.
Industry estimates, based on the current pace of trial readouts, suggest Eli Lilly may submit its New Drug Application to the FDA sometime in late 2026 or early 2027, with a possible approval decision roughly 10 months after that submission under standard FDA review timelines. However, it’s important to underline that no official regulatory timeline has been confirmed by Eli Lilly or the FDA, and these dates remain estimates that could shift depending on how the remaining trials perform.
In short, retatrutide has not been rejected or found unsafe by regulators. It simply has not yet completed the full body of Phase 3 evidence that the FDA requires before granting approval for any of its intended uses.
Wrap-Up
Glycated Hemoglobin (HbA1c) has earned its place as one of the most valuable numbers in modern medicine because it tells a story that no single blood glucose reading ever could: the story of how your body has handled sugar over months, not minutes. When that number stays high for too long, the consequences reach far beyond diabetes mellitus itself, quietly damaging the liver through fat accumulation and the kidneys through progressive filtration injury, largely through the same glycation and inflammatory processes that create Glycated Hemoglobin (HbA1c) in the first place.
Retatrutide represents one of the more promising developments in this space in recent years, not because it targets Glycated Hemoglobin (HbA1c) alone, but because its triple-hormone mechanism appears to address the interconnected nature of these conditions at the same time. The data so far, spanning Phase 2 and early Phase 3 trials, show substantial Glycated Hemoglobin (HbA1c) reductions, dramatic improvements in liver fat and steatosis, and encouraging early signals for kidney protection in diabetic kidney disease.
Still, encouraging data is not the same as an approved, available treatment. Retatrutide remains investigational, several major Phase 3 trials are still underway, and long-term outcome data proving durable kidney and cardiovascular protection will take more time to mature. Anyone managing diabetes, fatty liver disease, or kidney concerns today should continue working with their healthcare provider using currently approved tools and treatment guidelines, while watching this space with cautious, well-informed optimism as the TRIUMPH program continues to report results through 2026 and beyond.
