A Study of Retatrutide (LY3437943) in Participants With Type 2 Diabetes Mellitus Who Have Obesity or Overweight

Inclusion Criteria: * Have a body mass index (BMI) greater than or equal to 27.0 kilogram/square meter (kg/m ²) * Have Type 2 Diabetes (T2D) * Are on stable treatment for T2D for at least 90 days * Have a history of at least one unsuccessful dietary effort to lose body weight. GSA2 Inclusion Criteria * Previously diagnosed with OSA * Have AHI ≥15 on polysomnography at screening (definition of moderate-to-severe OSA) * For participants not on positive airway pressure (PAP) therapy: unable or unwilling to use PAP therapy and have not used PAP for at least 4 weeks prior to screening. * If on PAP therapy, have been on PAP therapy for at least 3 consecutive months prior to screening, and willing to temporarily stop using PAP therapy for approximately 7 days prior to each of the sleep study (PSG) visits. Exclusion Criteria: * Have a self-reported or documented change in body weight \>5 kg (11 pounds) within 90 days. * Have taken weight loss drugs, including over-the-counter medications, within 90 days prior to screening. * Have a prior or planned surgical treatment for obesity. * Have Type 1 diabetes * Have a family or personal history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN-2) * Have had pancreatitis GSA2 Exclusion Criteria * Use stimulants (for example, modafinil, armodafinil, solriamfetol, pitolisant, amphetamine) less than 3 months prior to screening. * Use hypnotics, mirtazapine, opioids, trazodone, and zonisamide less than 3 months prior to screening. * Use a dental appliance or other device to treat OSA other than PAP therapy.