The common sites
Retatrutide, like other subcutaneous GLP-1 peptides, is typically injected into the abdomen, the front or outer thigh, or the back of the upper arm. Each of these areas has enough subcutaneous fat to make injection technique straightforward and has been the standard site set used in trial protocols for similar drugs.
The abdomen
The abdomen is a commonly used site, generally injected at least a couple of inches away from the navel. It’s within easy reach for a self-injection, which is likely why it’s a common first choice.
Thighs and upper arms
The front and outer thigh are also commonly used and are easy to reach for a self-injection. The back of the upper arm is used as well but can be harder to reach alone, so it’s sometimes used with help from another person or skipped in a self-injection rotation.
Why rotating between sites matters
Repeatedly injecting the same small area can lead to lipohypertrophy, a lump of thickened tissue under the skin, which can affect how consistently the drug is absorbed. Rotating between the abdomen, thighs and arms spreads that wear out and keeps absorption more consistent week to week.
Logging the site each week
Noting which specific site and zone was used each week, alongside the date and dose, is what turns “I rotate sites” from a general intention into something that’s actually verifiable later.