Lilly reports tirzepatide lowered A1C by 2.23 points in children and teens with type 2 diabetes

Eli Lilly reported on Sept. 17, 2025 that its drug tirzepatide lowered A1C — a measure of average blood sugar over about three months — by an average of 2.23 percentage points in children and adolescents with type 2 diabetes, compared with a 0.05-point rise among those who received placebo ^[1][2]. The 30-week results come from SURPASS-PEDS, which Lilly described as the first Phase 3 trial of the medicine in this age group, and were presented at the European Association for the Study of Diabetes annual meeting and published at the same time in The Lancet ^[1][2].

What the trial did

SURPASS-PEDS enrolled 99 people aged 10 to under 18 whose type 2 diabetes was not adequately controlled with metformin, basal insulin or both ^[1][2]. They were randomly assigned at 39 sites in eight countries — the United States, Australia, Brazil, India, Israel, Italy, Mexico and the United Kingdom — to tirzepatide 5 mg (32 participants), tirzepatide 10 mg (33) or placebo (34), given as a once-weekly injection ^[1][2]. Participants were 61% female and 39% male, with a mean age of 14.7 years, a mean starting A1C of about 8.0%, a mean body mass index of roughly 35, and a mean weight of 96.6 kilograms; they had lived with diabetes for an average of 2.4 years ^[1][2][4]. The first 30 weeks were double-blind and placebo-controlled. Every participant then received tirzepatide in an open-label extension running to 52 weeks ^[1][2].

The numbers

The estimated treatment difference in A1C at 30 weeks was -2.28 percentage points (95% CI -2.87 to -1.69; p<0.0001) under the trial's efficacy estimand, which counts participants as if all had stayed on treatment for 30 weeks without needing rescue blood-sugar medicine ^[1]. Lilly's tables show A1C falling 2.2 points with pooled tirzepatide doses and 2.3 points with the 10 mg dose, against the 0.05-point rise on placebo, under the same measure. Under a second measure, the treatment-regimen estimand, which counts all randomized participants regardless of whether they stopped treatment, Lilly lists 2.0 points and 0.2 points ^[2][4]. The FDA prescribing information for Mounjaro reports the trial's A1C result under the treatment-regimen estimand as a least-squares mean difference of -1.8 percentage points (95% CI -2.4 to -1.2) ^[7]. The two estimands answer different questions and are not directly comparable.

Other 30-week results, under the efficacy estimand, were ^[2][4]:

• BMI fell 11.2% on the 10 mg dose, 7.4% on 5 mg and 9.3% pooled, compared with 0.4% on placebo.
• 86.1% of the 10 mg group reached an A1C of 6.5% or lower, compared with 27.8% on placebo.
• Fasting blood sugar fell 44.2 mg/dL pooled, from a starting average of 152 mg/dL, versus 7.9 mg/dL on placebo.

Glycemic control was sustained through 52 weeks of tirzepatide treatment, and Lilly said A1C improvements and BMI reductions continued through the extension ^[1][2].

Safety

The most common side effects were gastrointestinal and were mild to moderate, occurring mainly during dose increases ^[2][4]. Diarrhea was reported by 25% of participants on pooled tirzepatide doses versus 6% on placebo, nausea by 20% versus 9%, and vomiting by 14% versus 3% ^[2][4]. Discontinuation due to a side effect was 3% across pooled doses (6% at 5 mg, 0% at 10 mg) versus 0% on placebo; the Lancet reports two participants, or 6%, in the 5 mg group stopping the drug ^[1][2]. No severe hypoglycemia occurred, and 15.4% of tirzepatide-treated participants had a blood sugar reading below 54 mg/dL at some point through 30 weeks, versus 5.9% on placebo ^[2][4]. No deaths were reported ^[1]. The safety profile was consistent with what has been seen in adults ^[1][2].

Why it matters for patients

Type 2 diabetes in young people tends to progress faster than in adults, and treatment options are limited. The lead investigator, Dr. Tamara Hannon of Indiana University School of Medicine, said first-line treatments such as metformin and basal insulin often fail to control A1C in these patients ^[2][4].

Tirzepatide is sold as Mounjaro for type 2 diabetes and as Zepbound for adults with obesity, obstructive sleep apnea and weight-related conditions ^[2][4]. The FDA prescribing information for Mounjaro now lists pediatric patients 10 years of age and older, a labeling change dated December 2025, and sets a maximum of 10 mg once weekly for that age group, compared with 15 mg for adults ^[7].

The trial tested tirzepatide against placebo only, and only in young people already taking metformin, basal insulin or both; how it compares with other medicines in children has not been reported ^[1][2]. Whether the A1C and BMI improvements seen over one year lead to fewer diabetes complications later in life is not yet known.

What happens next

Lilly said it submitted the SURPASS-PEDS results to regulators worldwide for an expanded indication ^[2][4], and the FDA label now includes the pediatric use ^[7]. The trial is registered as NCT05260021 ^[1][2]. Longer-term pediatric data beyond the 52-week extension have not been disclosed.