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

Inclusion Criteria:

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, 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% 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

Exclusion Criteria:

* 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) 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