Which nerves can an injection reach?
Two areas cause most of the concern. The large sciatic nerve runs through the buttock, and the shoulder joint sits just above the deltoid. MedlinePlus describes the sciatic nerve as starting in the lower back and running down the back of each leg, where it controls muscles behind the knee and in the lower leg.
The CDC takes this seriously. Its vaccine administration chapter explains that the buttock is not used for vaccines in infants and children because of concern about sciatic nerve injury, and it gives precise landmarks for adults when the gluteal area is used. For the shoulder, the immunization guide built on CDC advice warns against injecting too high, near the bony point at the top of the shoulder, or too low.
What are the safe landmarks for each site?
Each site has bony points you can feel, and the injection goes where those points say, not where the muscle looks biggest.
| Site | Landmark | What to avoid |
|---|---|---|
| Upper outer buttock | Above and to the outside of a line from the bony dimple at the back of the pelvis to the bony point on the side of the hip | Going low or toward the midline |
| Ventrogluteal (side of hip) | Center of a triangle formed by the front point of the hip bone, the crest of the pelvis and the top of the thigh bone | Drifting backward toward the buttock |
| Outer thigh | Outer part of the middle third of the thigh | The front or inner thigh |
| Deltoid (shoulder) | Thickest part of the muscle, above armpit level, about 2 to 3 finger widths below the bony tip of the shoulder | Injecting too high near the joint, or too low |
The gluteal and ventrogluteal descriptions come from the CDC; the thigh and deltoid descriptions come from the immunization guide. Our step-by-step guide to intramuscular testosterone injections shows how to find each landmark on yourself.
What does nerve irritation feel like?
Different from ordinary soreness. MedlinePlus describes sciatic pain as anything from mild tingling, a dull ache or burning to sharp pain, often on one side, sometimes with numbness down the back of the calf or the sole of the foot, a weak leg, or a foot that catches on the ground when you walk.
If you feel a sudden, sharp or electric pain shooting down the leg while injecting, stop and withdraw the needle rather than finishing the dose in that spot, then call your provider. Soreness that stays at the injection site is a different problem, covered in our answer on injection site pain and swelling.
When should you get help?
Seek care the same day if you have weakness or numbness in the buttock, thigh or leg, pain traveling below the knee, or a foot that drags after an injection. Go to an emergency room for any loss of bladder or bowel control. MedlinePlus lists all of these as reasons to contact a provider right away.
For the shoulder, pain or stiffness that keeps getting worse, or that limits how far you can lift your arm in the days after a deltoid shot, deserves an exam rather than more injections into that arm.
Related question: does injecting under the skin avoid this?
For the sciatic nerve, yes. A review of subcutaneous testosterone notes there is no risk of sciatic injury with that route, and it uses smaller needles in the abdomen or thigh. Our guide on subcutaneous testosterone injections shows the technique, and the sibling answer on needle size for testosterone injections explains which needles suit each route.
How Ultimate Male teaches safe injection sites
If you inject at home, your provider shows you the landmarks for your chosen site and checks your technique, and you can return with questions at any follow-up. Injections can also be given in clinic in San Gabriel or Downey.
New pain, numbness or weakness after a shot should always be reported, even if it fades. To learn more about injectable testosterone therapy and the other forms available, start with the free 10-minute call.
