The study will be conducted in two parts (part A and part B). The main purpose of this study is to compare the amount of LY3209590 that gets into the blood stream and how long it takes the body to get rid of it, when self-administered at different body sites, abdominal wall, upper arm and thigh (part A), when administered by two different routes of injection, subcutaneously or intravenously (part B) in healthy participants.

The study may last up to 65 (part A) and 184 (part B) days, respectively.

Inclusion Criteria:

• Male or female participants who are overtly healthy as determined by medical evaluation
• Participants with body mass index (BMI) within the range 18.5 to 35.0 kilograms per meter squared (kg/m²)
• Male or female participants must agree to use contraception

Exclusion Criteria:

• Have a history of multiple or severe allergic reactions or a history of severe anaphylactic reaction
• Have known allergies to LY3209590, related compounds, or any components of the formulation
• Have an abnormality in the 12-lead electrocardiogram
• Intend to use prescription medication, including herbal medications and traditional medications
• Show evidence of human immunodeficiency virus infection or positive human immunodeficiency virus antibodies, hepatitis C or positive hepatitis C antibody, or hepatitis B or positive hepatitis B surface antigen
• Are lactating or pregnant