A Study of LY900014 and Insulin Lispro With an External Continuous Subcutaneous Insulin Infusion System in Adult Participants With Type 1 Diabetes

Inclusion Criteria: * Diagnosed with type 1 diabetes and have been using insulin continuously for at least 12 months. * Using an insulin pump with 'rapid-acting insulin' for at least 6 months and using the same rapid-acting insulin for at least the past 30 days. * Have experience using Continuous Glucose Monitoring (CGM) or Flash Glucose Monitoring (FGM) for at least 60 days during the past 12 months. * Have hemoglobin A1c values ≤8.5%, as determined by the central laboratory at screening. * Have a body mass index (BMI) of ≤35 kilograms per meter squared at screening. * Have been using the MiniMed 530G or 630G (US) or the MiniMed 640G (EU) insulin pump for at least the past 30 days. Exclusion Criteria: * Have had more than 1 emergency treatment for very low blood glucose in the last 6 months. * Have had more than 1 emergency treatment for poor glucose control (hyperglycemia or diabetic ketoacidosis) in the last 6 months. * Have significant insulin resistance defined as having received a total daily dose of insulin \>1.2 units per kilogram (U/kg) at screening, as determined by the average total daily insulin dose over the 3 days prior to screening divided by weight in kilograms based on investigator review of the participant's pump history. * Have significant lipohypertrophy, lipoatrophy, or scars within the subcutaneous tissue in areas of infusion or have a history of abscess at an infusion site within the last 90 days prior to screening. * Are receiving any oral or injectable medication intended for the treatment of diabetes mellitus other than rapid-acting analog insulin via CSII in the 90 days prior to screening. Occasional pen or syringe injection of insulin is allowed, for example, due to pump malfunction or unexplained hyperglycemia not responsive to pump correction bolus. * Taking certain diabetes medications that are not allowed for study participation. * Have major problems with heart, kidneys, liver, or have a blood disorder. * Have had or are now being treated for certain types of cancer that prevents study participation.