Subcutaneous injection sites, rotation and lipohypertrophy

The common subcutaneous injection sites are the abdomen, the front and outer thighs, the back of the upper arms and the upper buttocks or hips. Clinicians advise rotating between and within these areas because injecting the same spot repeatedly can cause lipohypertrophy, a lump of thickened fatty tissue under the skin. A written site log is the simplest way to keep a rotation going.

Use the sites and the technique your healthcare professional has shown you for your medicine. This guide explains the general picture and the record keeping.

Where the common sites are

These areas have a layer of fat under the skin, which is where a subcutaneous injection is meant to go. Some medicines are labelled for particular sites only, so check the leaflet.

Why rotate

Repeated injections into one small area can change the tissue there. Rotation spreads injections out so each spot has time to recover. The usual advice has two parts:

• Rotate between areas or sides, for example left abdomen, then right abdomen, then a thigh.
• Rotate within an area, placing each injection at least a finger's width away from the last one.

Avoid skin that is bruised, tender, scarred, hard or broken.

What is lipohypertrophy?

Lipohypertrophy is a build-up of fatty tissue under the skin at a place that has been injected many times. It shows up as a soft or rubbery lump or a thickened, raised area, and it is often easier to feel than to see. It has been studied most in people who inject insulin, where it is common.

It matters for two reasons:

1. A lump can take a long time to go down, and only does so if the area is rested.
2. Medicine injected into affected tissue may be absorbed unevenly, so the same dose can act differently from one injection to the next.

If you find a lump or a thickened patch, stop using that spot and show it to your healthcare professional.

How to keep track

Rotation fails when it relies on memory. A week later, most people cannot say which side they used. Record the site with every dose:

Before the next injection, look at the last few entries and pick somewhere that has rested. Note any redness, soreness or lumps on the entry for that site. A fuller method is in how to keep an injection site rotation log.

Doing it in an app

PepVault's injection site tracker has a front and back body map. Tap the site when you log a dose and it is saved with the entry, your history shows the site beside every dose, and a Suggest button proposes a site for the next one.

Common questions

Does it matter which site I use?

For some medicines absorption differs by site, and some are labelled for specific sites. Follow the leaflet and your clinician's instructions.

How far apart should injections in the same area be?

The usual guidance is at least a finger's width from the previous injection. Your clinician may give you a specific pattern.

Will a lump from repeated injections go away?

Lipohypertrophy often improves when the area is left alone, but it can take months. Have it checked rather than waiting to see.