A Study to Test Whether Survodutide Helps People With Type 2 Diabetes Control Their Blood Sugar

This study aims to find out whether a study medicine called survodutide helps people control their blood sugar. Adults who live with type 2 diabetes and with a body mass index (BMI) of 23 kg/m2 or higher can join. The study has 3 parts. In each part the study compares survodutide with placebo. Survodutide is being developed to treat several health problems including type 2 diabetes. Placebo looks like survodutide but does not contain any medicine. Depending on a person's diabetes treatment, a person will be assigned either to * Part A: healthy eating and physical activity * Part B: diabetes tablets (no injection of insulin) * Part C: injection of insulin (with or without diabetes tablets) Participants are randomly put into 1 of 3 groups, which means the group is chosen by chance. Two groups of participants get survodutide at different dose levels, and the third group gets placebo as injection under the skin once a week. You have a 2 in 3 chance of getting survodutide. During the study, participants continue their regular diabetes treatment. Participants are in the study for about 1 year and 2 months. During this time, they attend up to 12 visits at the site and receive at least 9 phone calls. Study doctors regularly test participants' blood sugar by checking their HbA1c values and other laboratory test results. The study doctor also regularly checks participants' health and takes note of any changes. For each study part, the results will be compared between the survodutide and the placebo group to see whether the treatment works.

Inclusion criteria: 1. Male or female, age ≥18 years at the time of signing informed consent, and at least the legal age of consent in countries where it is \>18 years 2. Diagnosed with type 2 diabetes mellitus (T2D) (e.g. American diabetes association (ADA)/European association for the study of diabetes (EASD) guidelines) and must meet requirements for one of background therapy parts A, B or C: 1. Part A: Naïve to insulin therapy and have not used oral or injectable anti-hyperglycaemic (diabetes) medication for at least 90 days prior to screening (Visit 1) and glycosylated haemoglobin A1c (HbA1c) ≥7.0 (≥53 mmol/mol) and \