Subcutaneous (SC) injection — administering a compound into the fatty tissue just beneath the skin — is the standard route for most injectable peptide drugs and many FDA-approved chronic-disease medications, including GLP-1 receptor agonists used for type 2 diabetes and chronic weight management. Correct technique matters for two reasons: it ensures consistent absorption (and therefore consistent dosing), and it minimizes the risk of injection-site problems such as bruising, lipohypertrophy, and infection.

Equipment

For prescription pen-injectors (such as Wegovy, Ozempic, Zepbound, Mounjaro, and Sermorelin Pen), the manufacturer-supplied pen needles are the appropriate sharps. For research peptides supplied as lyophilized powder requiring reconstitution, the equipment list typically includes bacteriostatic water, an appropriately sized mixing syringe, and unit-graduated insulin syringes (typically 0.3 mL or 0.5 mL) for daily dosing. Use a sterile needle for every injection — never reuse needles.

The Nine-Step Technique

1. Wash and prepare hands

Wash hands thoroughly with soap and warm water for at least 20 seconds. Dry with a clean towel. Hand hygiene is the single most effective step in preventing injection-site infection.

2. Inspect the medication or research compound

Verify the label, dose, and expiration. The solution should be clear (or as described in the prescribing information). Discard any solution that is cloudy, discolored, or contains particulates. Reconstituted peptides have specific storage and use-by windows that should be respected — typically refrigerated and used within a defined number of days, depending on the compound and bacteriostatic water used.

3. Choose the injection site

Common subcutaneous sites include:

Abdomen: at least 2 inches (5 cm) away from the navel. Typically the most predictable absorption.
Front of the thighs: the upper outer area, away from the knee and groin.
Back of the upper arms: useful when self-administered with a partner or specific hardware.

Avoid scarred, bruised, inflamed, or tattooed skin. Avoid the waistband area where clothing rubs against the site.

4. Rotate sites

Use a different site for each injection. Rotate within an area (for example, walking around the abdomen in a clock pattern) and across areas (abdomen → thighs → arms). Site rotation reduces the risk of lipohypertrophy — a thickening of subcutaneous fat caused by repeated injections at the same site, which can alter absorption and produce visible lumps.

5. Clean the skin

Wipe the chosen site with an alcohol pad and allow it to air-dry for several seconds. Injecting through wet alcohol can sting and cause irritation.

6. Pinch and inject

Gently pinch a fold of skin and subcutaneous tissue. Insert the needle at the angle recommended for the needle length and your body composition — typically 90° for shorter (4–6 mm) needles, and 45° for longer needles in lean tissue. Press the plunger steadily until all medication is delivered. With pen-injectors, hold the pen in place for the manufacturer-specified count after the dose completes (often 6–10 seconds) to ensure full delivery.

7. Withdraw and apply gentle pressure

Remove the needle at the same angle it was inserted. Apply gentle pressure with a clean tissue or cotton pad. Do not rub the site; rubbing can affect absorption and increase bruising.

8. Dispose of the needle safely

Place used needles and pen needles directly into an FDA-cleared sharps container. Never recap a used needle, never put sharps in household trash, and never place loose sharps in recycling. Consult local pharmacy take-back programs for full sharps containers, or check the safe-needle-disposal program in your state.

9. Log the injection

Record the date, time, site used, dose, and any observations (pain, bruising, lump, irritation). Adherence and site-rotation patterns are easier to maintain when logged consistently. Companion apps such as PeptideTracker are designed to operationalize this step with site-rotation reminders, dose history, and side-effect tracking.

Common Issues

Bruising at the injection site

Minor bruising is common and usually resolves within a few days. Causes include hitting a small surface vessel, injecting too quickly, rubbing the site afterward, or concurrent use of anticoagulant or antiplatelet medications. If bruising is severe, persistent, or accompanied by significant swelling, contact the prescribing clinician.

Lump or thickened tissue at recurrent sites

Lipohypertrophy is the term for the firm, lumpy tissue that can develop with repeated injections at the same site. Affected sites absorb medication unpredictably. The remedy is consistent site rotation. Pre-existing lipohypertrophy is best evaluated by a clinician.

Pain, redness, warmth, or pus

These are signs of possible injection-site infection. Stop using the affected site and contact the prescribing clinician promptly. Hand hygiene, sterile technique, and never reusing needles are the primary preventive measures.

Subcutaneous Injection TechniqueA Research and Educational Reference