Retatrutide Injection: Complete Subcutaneous Injection Guide

Subcutaneous Injection Basics

Retatrutide is administered as a subcutaneous injection, meaning the needle goes into the fatty tissue just beneath the skin rather than into muscle or vein. The injection is performed using an insulin syringe with a fine-gauge needle — typically 30G to 31G, which is thin enough that most people feel minimal discomfort. The injection volume varies by dose and reconstitution ratio. At the standard concentration of 5 mg/mL used in the TRIUMPH clinical trials, a 2 mg dose requires 0.4 mL or 40 units on a 100-unit insulin syringe.

Rotating Injection Sites

Rotating injection sites with each dose reduces the risk of lipohypertrophy — a buildup of fatty tissue under the skin that can interfere with drug absorption. The recommended rotation schedule for retatrutide follows the same pattern used for insulin: alternate between the left and right sides of the abdomen, and between the abdomen and the thighs on a weekly rotation. The upper arm can also be used if someone else is administering the injection. Keeping a simple log of injection sites helps ensure proper rotation and prevents overuse of any single site.