A Study of LY4057996 in Healthy Participants and Participants With Type 1 and Type 2 Diabetes

Who May Qualify: Part A for Healthy Participants: - Are overtly healthy as determined by medical evaluation, including medical history, physical exam, laboratory tests, and cardiac screening assessment Part A for Type 2 Diabetes (T2DM) Participants: - Are participants with T2DM diagnosed greater than 1 year before enrollment, - On basal insulin therapy, insulin glargine, insulin detemir, or insulin degludec, greater than 10 units per day for at least 6 months (for Cohort 5 only) - Glycated hemoglobin (HbA1c) 6.5% to 9.5% inclusive at screening Part B - Have Type 1 Diabetes (T1D) for at least 1 year with a fasting C-peptide level of 0.20 nanomole per liter (nmol/L) or less or non-fasting C-peptide level of 0.30 nmol/L or less at screening - HbA1c 6% to 8.5% inclusive at screening Part C - Have T1D for at least 1 year with a fasting C-peptide level of 0.20 nanomole per liter (nmol/L) or less or non-fasting C-peptide level of 0.30 nmol/L or less at screening - HbA1c 6 to 8.5% inclusive at screening All Parts - Have blood pressure of less than 140/90 millimeters of mercury (mmHg) for healthy participants or 150/90 mmHg for participants with diabetes and pulse rate of less than 90 beats per minute (bpm) (supine) - No hypoglycemia unawareness for all Type 1 and Type 2 Diabetes participants Who Should NOT Join This Trial: - Have had more than 1 emergency room visit or hospitalization due to poor glucose control (hyperglycemia or diabetic ketoacidosis) within 6 months prior to screening - Have had any episodes of severe hypoglycemia (defined as requiring assistance due to neurologically disabling hypoglycemia), hypoglycemia unawareness, or both within the 6 months prior to screening All Parts - Cardiovascular: no significant history of cardiovascular disease (CVD) - Gastrointestinal: have gastroparesis or have undergone gastric surgery - Hepatic: have acute or chronic hepatitis Always talk to your doctor about whether this trial is right for you.