Subcutaneous Injection 101: Technique, Sites, and Mistakes That Cause Bruising

May 3, 2026 · Education

“SubQ” (subcutaneous) means injecting into the fat layer just under the skin — not into muscle. It’s the standard route for almost every peptide. Done right, it’s essentially painless and leaves no mark. Done wrong, you get bruises, lumps, and unnecessary pain.

SubQ vs. IM

Almost all peptides in our catalog (BPC-157, TB-500, GHK-Cu, CJC/Ipa, MOTS-c, Tirzepatide, etc.) are subQ.

Equipment

• Insulin syringe, 29-31 gauge, 5/16″ or 1/2″ length, U-100 — this is the standard. Brands like BD Ultra-Fine, EasyTouch, or NovoFine all work.
• Alcohol swabs (70% isopropyl).
• Sharps container.

Smaller gauge numbers = thicker needle. 31 gauge is thinner than 29 gauge and hurts less. 5/16″ is shorter than 1/2″ and is plenty for subQ on most adults.

Best injection sites

1. Abdomen — below the navel, 2 inches off-center on either side. Largest area of subcutaneous fat. Most common site.
2. Front of thighs — outer third, halfway between hip and knee.
3. Upper outer hip / love handle area — if you have enough fat to pinch.
4. Back of upper arm — harder to reach for self-injection.

Avoid: directly over the navel, scarred skin, visible veins, areas of recent bruising.

Step-by-step technique

1. Wash hands with soap and water.
2. Draw the dose. Tap any large air bubbles to the top and gently push them out (small bubbles don’t matter for subQ).
3. Choose a site at least 1 inch from your last injection.
4. Swab the skin with alcohol. Let it dry — injecting into wet alcohol stings.
5. Pinch the skin gently with your non-dominant hand to lift the subQ tissue away from muscle.
6. Insert at 90 degrees if you have visible fat, or 45 degrees if you’re very lean. The full needle goes in.
7. Release the pinch — you don’t need to maintain it during injection.
8. Press the plunger slowly — 3-5 seconds for most volumes. GHK-Cu and NAD+ should be even slower (15-30 seconds).
9. Pull straight out at the same angle you went in.
10. Apply gentle pressure with a clean tissue or cotton ball for 5-10 seconds. Don’t rub.
11. Dispose of the syringe in your sharps container immediately.

Avoiding bruises

Bruises happen when the needle nicks a small capillary on the way in or out. Three habits prevent most of them:

• Don’t rub after injection. Pressure, not friction. Rubbing turns a small bleed into a visible bruise.
• Use 31 gauge if you bruise easily. The smaller diameter does less damage on entry.
• Inject slowly. Fast injection forces fluid into a tight space and increases tissue damage.

If you do bruise, switch sides for the next few injections. The bruise itself is harmless and resolves in 5-7 days.

Site rotation

Repeating injections in the same exact spot causes:

• Lipohypertrophy (lumpy fat tissue) over weeks/months.
• Reduced absorption in the affected area.
• Increased sensitivity and pain at that site.

Simple rotation strategy: divide the abdomen into a clock face, move 1-2 hours each day. After working around the clock once, switch to thighs or hips for a week. Repeat.

Common mistakes

• Hitting muscle. If your insulin syringe hits muscle on a thin person, the injection becomes IM by accident — faster absorption, more pain. Use 5/16″ or pinch more skin.
• Aspiration. You don’t need to pull back to check for blood with subQ — that’s an IM technique. SubQ tissue has minimal vasculature.
• Reusing needles. Don’t. Even one reuse dulls the needle and increases pain dramatically.
• Injecting cold solution. Refrigerator-cold peptides sting. Warm the syringe in your hand for 60 seconds first.
• Wet alcohol. Always let the swab dry before injecting.

Disclaimer: Educational content only. Always work with a healthcare provider familiar with peptide therapy.