Study Results

Retatrutide for Type 2 Diabetes: What the Phase 3 Trials Show

Results from TRANSCEND-T2D-1 and TRIUMPH-2, the two Phase 3 trials of retatrutide in type 2 diabetes: A1C, weight, blood sugar targets, low blood sugar and side effects.

Written By

retaweightloss.com

Updated on

06 Oct 2026

Time to read

5 min read

Retatrutide and Type 2 Diabetes: The Short Answer

Retatrutide, an investigational weekly injection that acts on GIP, GLP-1 and glucagon receptors, has been tested in two Phase 3 trials in people with type 2 diabetes. In both, it lowered A1C (average blood sugar over about three months) and body weight more than placebo.

TRANSCEND-T2D-1 (40 weeks, 537 people whose diabetes was not controlled by diet and exercise alone): A1C fell by up to 1.94 percentage points counting everyone randomized, compared with 0.81 on placebo, and weight by up to 15.3%, compared with 2.6%.
TRIUMPH-2 (80 weeks, 1,152 people with type 2 diabetes and obesity or overweight): its developer reports A1C reductions of up to 1.6 points, compared with 0.2 on placebo, and weight loss of up to 20.8%, compared with 4.0%, if taken as intended.

Retatrutide is not approved for diabetes or any other use.

TRANSCEND-T2D-1: Retatrutide on Its Own

TRANSCEND-T2D-1 tested retatrutide as the only diabetes medicine in adults whose type 2 diabetes was inadequately controlled with diet and exercise alone. Participants had an A1C of 7.0% to 9.5% and a BMI of 23 or more, and were randomly assigned to retatrutide 4 mg, 9 mg or 12 mg, or placebo, for 40 weeks at 48 sites in India, Mexico and the United States. On average they had had diabetes for 2.5 years, with an A1C of 7.9%, a BMI of 35.8 and a weight of 96.9 kg (about 214 lb).

The company presented the results at the American Diabetes Association meeting on June 6, 2026, when they were also published in The Lancet. The figures below come from the developer's medical information summary of the trial (reviewed May 2026). The primary end point was the change in A1C at week 40; results for 4 mg were treated as additional secondary end points.

Group	A1C, everyone randomized	A1C, taken as intended	Weight, everyone randomized	Weight, taken as intended
Retatrutide 4 mg	−1.69	−1.69	−11.5%	−11.5%
Retatrutide 9 mg	−1.86	−2.01	−13.9%	−15.5%
Retatrutide 12 mg	−1.94	−1.93	−15.3%	−16.8%
Placebo	−0.81	−0.78	−2.6%	−2.5%

The company's headline figures, "up to 2.0%" for A1C and 16.8% for weight, are the efficacy-estimand results for 9 mg and 12 mg respectively. It noted that weight loss had not yet plateaued at 40 weeks.

Many participants reached common A1C targets (counting everyone randomized; the efficacy-estimand figures are a few points higher, up to 90%, 85% and 46%):

A1C target	4 mg	9 mg	12 mg	Placebo
Below 7.0%	82%	83%	89%	52%
6.5% or below	75%	76%	83%	40%
Below 5.7%	35%	40%	37%	14%

Counting everyone randomized, fasting blood sugar fell by about 30 to 32 mg/dL on retatrutide, compared with 1.0 mg/dL on placebo; systolic blood pressure fell by 4.7 to 5.4 mmHg, compared with 1.5 on placebo, and triglycerides by 26.7% to 34.1%, compared with 3.4%.

TRIUMPH-2: People With Diabetes and Obesity

TRIUMPH-2 enrolled 1,152 adults with type 2 diabetes and obesity or overweight, randomly assigned in equal numbers to retatrutide 4 mg, 9 mg or 12 mg, or placebo, for 80 weeks. At the start they averaged a BMI of 38.2, a weight of 106.4 kg (234.6 lb) and an A1C of 7.7%. Topline results were announced on July 23, 2026, and the full results were published in The Lancet on September 29, 2026. The figures below are from the company's announcements, which use the efficacy estimand.

Group	Weight change	A1C change	A1C 6.5% or below	A1C below 5.7%
Retatrutide 4 mg	−12.7%	−1.4	73.1%	28.4%
Retatrutide 9 mg	−19.1%	−1.6	79.2%	40.0%
Retatrutide 12 mg	−20.8%	−1.5	79.0%	39.3%
Placebo	−4.0%	−0.2	26.3%	4.4%

Among people on 12 mg, 52.0% lost at least 20% of their body weight, compared with 1.5% on placebo, and 59.5% no longer met the BMI criteria for obesity. In those who started with a BMI of 35 or more, the 12 mg group lost 23.4% on average. On 12 mg, systolic blood pressure fell by 10.8 mmHg, triglycerides by 39.5% and non-HDL cholesterol by 19.6%.

Why Weight Loss Was Lower Than in the Obesity Trials

In TRIUMPH-1, in people with obesity and without diabetes, retatrutide 12 mg reduced weight by 28.3% at 80 weeks if taken as intended. In TRIUMPH-2, also 80 weeks, the figure was 20.8%, and in the shorter TRANSCEND-T2D-1 it was 16.8% at 40 weeks. The trials differ in their participants, length and background treatment, so these figures show the gap but not its cause.

Low Blood Sugar (Hypoglycemia)

In TRANSCEND-T2D-1, where retatrutide was used without other diabetes medicines, blood sugar below 54 mg/dL was recorded in no one on 4 mg, 2 people (2%) on 9 mg and 1 person (1%) on 12 mg, compared with no one on placebo. There was no severe hypoglycemia in any group. The TRIUMPH-2 announcements do not report hypoglycemia rates.

For approved GLP-1-based medicines, the risk of low blood sugar is higher when they are combined with insulin or a sulfonylurea; the US label for tirzepatide, for example, carries that warning. TRANSCEND-T2D-1 did not test retatrutide with those medicines.

Side Effects in the Diabetes Trials

As in the obesity trials, the most common side effects were gastrointestinal. In TRANSCEND-T2D-1, the developer describes them as mostly mild to moderate, occurring mainly while the dose was being increased and subsiding over time.

Side effect	TRANSCEND-T2D-1 (4 / 9 / 12 mg vs placebo)	TRIUMPH-2 (4 / 9 / 12 mg vs placebo)
Nausea	16.4% / 19.5% / 26.5% vs 3.7%	13.7% / 20.8% / 28.0% vs 8.0%
Diarrhea	18.7% / 26.3% / 22.8% vs 4.5%	27.4% / 33.5% / 33.6% vs 13.2%
Vomiting	15.7% / 15.0% / 17.6% vs 2.2%	5.5% / 10.2% / 15.7% vs 4.2%
Dysesthesia (skin sensation)	4.5% / 2.3% / 4.4% vs 0.0%	4.5% / 5.6% / 7.3% vs 0.7%
Stopped because of side effects	2.2% / 4.5% / 5.1% vs 0.0%	3.8% / 11.6% / 7.7% vs 4.9%

In TRIUMPH-2, more people stopped treatment because of side effects on 9 mg (11.6%) than on 12 mg (7.7%), a pattern the announcement does not explain. Comparing these rates with the obesity trials is not reliable, because the trials differ in length, population and dose. Dysesthesia on 12 mg was reported less often in both diabetes trials (4.4% and 7.3%) than in TRIUMPH-1 (12.5%).

Can Retatrutide Prevent Type 2 Diabetes?

No trial has been designed to test this. TRANSCEND-T2D-1 and TRIUMPH-2 enrolled people who already had type 2 diabetes, and none of the retatrutide obesity trials listed on the developer's medical information site is a diabetes prevention trial, as far as we found.

The closest data come from TRIUMPH-1, a weight-loss trial in people without diabetes. Among participants who had prediabetes at the start, blood sugar had returned to the normal range by week 80 in 89.4% to 93.2% of those on retatrutide, compared with 54.2% on placebo. These were not the trial's main goals, and longer follow-up would be needed to show whether retatrutide prevents diabetes.

Is Retatrutide Approved for Diabetes?

No. Retatrutide is not approved for any use. Lilly says it plans to submit a Biologics License Application to the US Food and Drug Administration in the first quarter of 2027. Which uses that application will cover, and whether they will be approved, is not yet known.

Sources

Lilly Medical. TRANSCEND-T2D-1 trial summary (retatrutide monotherapy in type 2 diabetes). Reviewed May 2026.
Eli Lilly. Lilly's triple agonist, retatrutide, drove substantial improvements in weight, A1C, knee osteoarthritis pain, and obstructive sleep apnea, demonstrating its remarkable potential to treat obesity and its complications. June 6, 2026.
Eli Lilly. Lilly's triple agonist, retatrutide, successful in two additional Phase 3 obesity trials, delivering significant improvements in weight and A1C. July 23, 2026. (TRIUMPH-2, TRIUMPH-3)
Eli Lilly. Lilly's triple agonist, retatrutide, delivered substantial weight loss and A1C reduction, underscoring its potential promise for people with obesity and type 2 diabetes. September 29, 2026. (TRIUMPH-2)
Jastreboff AM, Kaplan LM, Davies MJ, et al. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity. N Engl J Med. Published September 29, 2026. DOI: 10.1056/NEJMoa2604169. (TRIUMPH-1, prediabetes data)
Eli Lilly. US prescribing information for tirzepatide for weight reduction, section 5. Revised August 2026.

Medical Disclaimer: This article summarizes clinical trial results for general information only and is not medical advice. Retatrutide is investigational and is not approved by the FDA for any use. It is not available by prescription, and products sold online under its name are not sold or supplied by Lilly. Nothing here is a recommendation to use, seek out, change or stop any medication.

Frequently asked questions

Does retatrutide lower A1C?

Yes, in its trials. In TRANSCEND-T2D-1, A1C fell by 1.69 to 1.94 percentage points over 40 weeks counting everyone randomized, compared with 0.81 on placebo. In TRIUMPH-2, its developer reports reductions of 1.4 to 1.6 points over 80 weeks if taken as intended, compared with 0.2 on placebo.

How much weight do people with type 2 diabetes lose on retatrutide?

Less than in the obesity trials. In TRIUMPH-2, people on 12 mg lost 20.8% of their weight at 80 weeks if taken as intended, compared with 4.0% on placebo. In the 40-week TRANSCEND-T2D-1, the 12 mg figure was 16.8%, or 15.3% counting everyone randomized.

Does retatrutide cause low blood sugar?

In TRANSCEND-T2D-1, where it was used without other diabetes medicines, 3 people on retatrutide and no one on placebo had blood sugar below 54 mg/dL, and no one had severe hypoglycemia. For approved GLP-1-based medicines, the risk is higher with insulin or a sulfonylurea, combinations that trial did not test.

Can retatrutide prevent type 2 diabetes?

That has not been tested; no retatrutide trial was designed for it, as far as we found. In TRIUMPH-1, a weight-loss trial, blood sugar returned to the normal range by week 80 in 89.4% to 93.2% of participants with prediabetes on retatrutide, compared with 54.2% on placebo. This was not the trial's main goal.

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