The safest spot for an intramuscular injection in the buttock is the ventrogluteal site, located on the upper side of the hip rather than the fleshy center of the buttock that most people picture. The traditional “upper outer quadrant” of the buttock, known as the dorsogluteal site, is the one most people are familiar with, but research over the past few decades has steadily shifted clinical recommendations toward the ventrogluteal area because it sits farther from the sciatic nerve and major blood vessels while offering thicker underlying muscle.
Where Exactly Is the Ventrogluteal Site
The ventrogluteal site sits over the gluteus medius and gluteus minimus muscles on the lateral side of the hip. To locate it on another person, place the heel of your opposite hand on the greater trochanter, the bony knob you can feel at the top of the outer thigh. Point your index finger toward the front of the hip bone (the anterior superior iliac spine) and spread your middle finger back toward the iliac crest, the curved ridge of bone along the top of the pelvis. The injection goes into the V-shaped triangle formed between those two fingers. The muscle in that triangle is thick, well-defined, and covered by relatively little fat compared to the rest of the buttock.
Ultrasound and CT studies consistently show that the ventrogluteal site has more muscle and less subcutaneous fat than the dorsogluteal site. In older adults, for example, one study measured average muscle thickness at the ventrogluteal site at about 40 mm compared to roughly 26 mm at the dorsogluteal site, while subcutaneous fat was thinner at the ventrogluteal location.1International Journal of Older People Nursing. Examining the Safety of Dorsogluteal and Ventrogluteal Sites for Intramuscular Injection in Older Adults A meta-analysis pooling data across multiple adult populations found similar patterns, with ventrogluteal muscle thickness averaging around 36 to 38 mm and subcutaneous tissue around 20 mm, depending on the landmarking method used.2PubMed Central. Gluteal muscle and subcutaneous tissue thicknesses in adults: a systematic review and meta-analysis More muscle means the needle is more likely to deposit medication where it belongs.
Why the Traditional Upper Outer Quadrant Is Riskier
The dorsogluteal site, the classic spot people think of when they hear “butt injection,” sits in the upper outer quadrant of the buttock over the gluteus maximus. It has been used for decades simply because it is easy to find on most body types. The problem is that the sciatic nerve, the largest nerve in the body, runs through the gluteal region, and a misplaced injection at the dorsogluteal site can hit it. The sciatic nerve is the most commonly injured nerve from intramuscular injections worldwide, and the buttock is the injection site most associated with that injury.3PubMed Central. Iatrogenic Injury to the Sciatic Nerve due to Intramuscular Injection: A Case Report Children, elderly adults, and underweight individuals are especially vulnerable because they have less tissue padding between the skin surface and the nerve.4Journal of International Medical Research. Sciatic nerve injection injury
Beyond nerve injury, the dorsogluteal region contains the superior gluteal artery. Accidental injection into or near this artery can cause catastrophic outcomes. Case reports have documented tissue necrosis in infants following inadvertent intra-arterial injection of penicillin into the buttock.5American Journal of Diseases of Children. Accidental Intra-Arterial Injection of Penicillin In one case, injection into the superior gluteal artery was believed to have caused medication to travel upstream and occlude the spinal artery, resulting in spinal cord damage.6PubMed. Spinal cord lesion after penicillin gluteal injection The ventrogluteal site avoids both the sciatic nerve and these major arterial branches, which is the core reason clinical guidelines increasingly favor it.
How Often Gluteal Injections Actually Reach Muscle
One of the most striking findings in this field is how frequently injections intended for muscle end up in fat instead. CT-verified studies have found that only about 32 to 52% of intended intramuscular gluteal injections actually reach muscle tissue. In one study, just 32% of injections landed in muscle overall, and when broken down by sex, only 8% of injections in women reached muscle compared to 56% in men.7PubMed Central. A narrative review of the success of intramuscular gluteal injections and its impact in psychiatry That is a startling failure rate for a procedure performed millions of times a day worldwide.
When medication lands in fat rather than muscle, it absorbs more slowly and unpredictably, which can mean the drug does not reach therapeutic levels as quickly as intended. The subcutaneous tissue is also less vascularized, making it more susceptible to infection and local reactions.8PubMed Central. Necrotizing Soft Tissue Fasciitis after Intramuscular Injection In a study of buttock injection complications in children, about 91% of local complications, including abscesses, cellulitis, and fat necrosis, developed in fat tissue rather than in muscle, reinforcing that inadvertent subcutaneous deposition is the main driver of problems.9Journal of the Korean Association of Pediatric Surgeons. Local Complications after Intramuscular Injections in the Buttock in Children
Choosing the Right Needle Length
Much of the failure to reach muscle comes down to needle length. A standard 1.5-inch (about 38 mm) needle works for many people, but not all. The depth of subcutaneous fat varies enormously depending on body size, sex, and injection site, and a needle that works well for a lean man may deposit medication entirely within the fat layer of a woman with a higher BMI.
A systematic review found that standard-length needles frequently fail to reach muscle at the dorsogluteal site in people with BMIs above 25, with women especially likely to receive inadvertent subcutaneous injections due to greater fat thickness.10PubMed. Dorsogluteal intramuscular injection depth needed to reach muscle tissue according to body mass index and gender: A systematic review At the ventrogluteal site, research suggests that a 1.5-inch needle has an expected failure rate of about 71% in women with a BMI over 30 and roughly 60% in men with a BMI over 35.11American Journal of Therapeutics. Body Mass Index: A Reliable Predictor of Subcutaneous Fat Thickness and Needle Length for Ventral Gluteal Intramuscular Injections
Recommended needle lengths vary based on body composition. For the ventrogluteal site, guidelines suggest ranges from roughly 20 mm in thin women to as long as 88 mm in obese women, and from about 23 mm in thin men up to 82 mm in obese men.12Medical Research Archives. Intramuscular Injection Guideline Revisions are Needed Based on Body Mass Index, Needle Length, Sex, and Skin to Muscle Depth The practical takeaway is that needle selection should be individualized. If you or the person giving the injection is working with a standard 1.5-inch needle and you have a higher BMI, the injection may not be reaching muscle.
Subcutaneous Fat Differences Between the Sites and Between Sexes
Women tend to carry more subcutaneous fat in the gluteal region than men do, which is a significant factor in injection success. One cross-sectional study found subcutaneous fat was significantly thicker in women than in men at both the dorsogluteal and ventrogluteal sites, with a more pronounced difference at the dorsogluteal site.13PubMed. Ventrogluteal versus dorsogluteal site selection: A cross-sectional study of muscle and subcutaneous fat thicknesses and an algorithm incorporating demographic and anthropometric data to predict injection outcome The meta-analysis data support this as well, showing that females had significantly thicker subcutaneous tissue at the ventrogluteal site than males.2PubMed Central. Gluteal muscle and subcutaneous tissue thicknesses in adults: a systematic review and meta-analysis
For people with higher BMIs, one recommendation is to avoid bunching the skin before inserting the needle. Bunching, or pinching up a fold of tissue, is sometimes taught as a way to stabilize the site, but in obese individuals it can add extra tissue between the needle tip and the muscle, making it even harder for the needle to reach.7PubMed Central. A narrative review of the success of intramuscular gluteal injections and its impact in psychiatry For highly obese populations, some researchers have suggested that the gluteal route should be avoided entirely for most drugs, or that substantially longer needles should be used when no alternative route is available.14BMJ. Intramuscular gluteal injections in the increasingly obese population: retrospective study
Injection Technique and the Z-Track Method
Once you have located the correct site and chosen the appropriate needle, technique matters. The Z-track method involves pulling the skin and subcutaneous tissue to one side before inserting the needle, injecting the medication, then releasing the skin after withdrawing the needle. This creates a zigzag path through the tissue that helps seal the medication in the muscle and prevent it from leaking back along the needle track into the subcutaneous layer or onto the skin.
Research shows the Z-track method reduces drug leakage compared to the standard straight-in technique. One study found significantly less drug leakage with Z-track, though pain scores between the two methods did not differ significantly.15PubMed. The Effect of the Z-Track Technique on Pain and Drug Leakage in Intramuscular Injections A systematic review and meta-analysis confirmed that Z-track reduces leakage but does not appear to significantly lower injection pain on its own.16PLoS ONE. The effect of intramuscular injection technique on injection associated pain; a systematic review and meta-analysis A separate trial in patients receiving magnesium sulfate injections found that Z-track reduced not only leakage but also gluteal inflammation.17International Journal of Research in Medical Sciences. Z-track technique reduces pain at the injection site, drug leakage, post-injection gluteal inflammation in Pritchard regimen for severe pre-eclamptic patients: findings from a randomized controlled trial Overall, Z-track is a simple tweak to standard technique that costs nothing and reduces at least one common problem.
Patient Positioning for Less Pain
How you position yourself during the injection can affect both comfort and how well the muscle relaxes. A tense gluteal muscle makes the injection hurt more and can make it harder for the needle to penetrate properly. Lying face-down (prone) with your toes pointed inward naturally relaxes the gluteal muscles. A study comparing prone and side-lying positions found that prone positioning resulted in significantly lower pain intensity and higher comfort levels.18Mediterranean Nursing and Midwifery. The Effect of Different Lying Positions on Regional Pain and Comfort Levels in Intramuscular Drug Administration
If lying prone is not practical, lying on your side with the upper leg bent forward and the lower leg straight also helps relax the gluteal area. Standing is the worst option because the muscles tend to be tensed, which increases pain and makes accurate landmarking more difficult.
Ventrogluteal Versus Dorsogluteal for Pain
Beyond safety, there is a comfort argument for the ventrogluteal site. A meta-analysis pooling nine studies found that pain was significantly lower at the ventrogluteal site compared to the dorsogluteal site.19PubMed Central. Adverse effects of dorsogluteal intramuscular injection versus ventrogluteal intramuscular injection: A systematic review and meta‐analysis A separate review focused specifically on analgesic and anti-inflammatory drugs reached the same conclusion, grading the evidence as moderate in quality.20Enfermería Actual de Costa Rica. Pain in the administration of drugs by intramuscular injection: ventrogluteal vs dorsogluteal The likely reason is that the ventrogluteal site has fewer sensory nerve endings in the overlying tissue and the muscle itself is more accessible without passing through thick fat layers.
Should You Aspirate Before Injecting
Aspiration, pulling back on the plunger briefly before injecting to check for blood return, was long taught as a universal step in intramuscular injection technique. The idea was to confirm the needle had not entered a blood vessel. Both the World Health Organization and the Centers for Disease Control and Prevention no longer recommend routine aspiration for intramuscular injections.21Clinical Nursing Research. Blood Aspiration During IM Injection
The reasoning is that the ventrogluteal, deltoid, and vastus lateralis sites do not have large blood vessels close enough to the injection zone to justify the extra step, which prolongs the procedure and can increase pain by moving the needle tip around in the tissue. The one exception noted in the literature is the dorsogluteal site, where aspiration is still recommended because of its proximity to the gluteal artery.22Journal of Clinical Nursing. Aspirating during the intramuscular injection procedure: a systematic literature review This is yet another reason the ventrogluteal site simplifies the procedure: you can skip the aspiration step entirely.
Gluteal Injections in Children
In young children, the gluteal muscles are not well developed, which makes the buttock a less reliable injection site. The preferred sites for infants and toddlers are the vastus lateralis muscle on the outer thigh and, in older children, the deltoid in the upper arm. When gluteal injections are given to children, the two most common serious complications are muscle contractures and sciatic nerve injury.23PubMed. Intramuscular injections in children
The thigh is generally the safest alternative in children. A cadaver and imaging study found that the middle of the vastus lateralis muscle carried no major blood vessels or nerve branches, unlike the rectus femoris where the descending branch of the lateral circumflex femoral artery and femoral nerve branches were present.24PubMed Central. Anatomically safe sites for intramuscular injections: a cross-sectional study on young adults and cadavers with a focus on the thigh For adults who cannot use the gluteal site, the mid-thigh vastus lateralis is a well-studied backup.
What Happens When Injections Go Wrong
Most intramuscular injections, even imperfectly placed ones, cause no lasting harm. But the range of possible complications is worth knowing, especially for anyone administering injections regularly. Local complications include abscesses, cellulitis, and fat necrosis, the majority of which stem from medication being deposited in fat rather than muscle.9Journal of the Korean Association of Pediatric Surgeons. Local Complications after Intramuscular Injections in the Buttock in Children Depot medications, which are designed to release slowly from the injection site, can occasionally provoke granulomatous masses that mimic tumors on imaging.25PubMed. Imaging of recurrent intramuscular granulomatous masses induced by depot injection of leuprorelin
In rare cases, injection-site infections can escalate into necrotizing soft tissue infections, a life-threatening emergency. A review of published cases found 19 reported instances of necrotizing fasciitis following intramuscular injection, emphasizing that even correctly administered injections can introduce enough local trauma to serve as a portal for infection.8PubMed Central. Necrotizing Soft Tissue Fasciitis after Intramuscular Injection Signs to watch for include rapidly spreading redness, severe pain disproportionate to the injection, swelling, fever, and skin that feels warm or crackly to the touch. These symptoms warrant immediate medical attention.
Ultrasound-Guided Injections
For medications where accurate muscle deposition is especially critical, such as long-acting injectable antiretrovirals, some clinics have started using point-of-care ultrasound to guide needle placement. A study of long-acting cabotegravir and rilpivirine injections found that ultrasound guidance confirmed intramuscular placement in 75% of injections and reduced injection-site reactions by about 16% compared to unguided injections, with significantly less induration and redness. The unguided group also had a higher proportion of drug concentrations falling below the target threshold.26AIDS. Point-of-care ultrasound guidance for long-acting cabotegravir–rilpivirine administration improves injection-site tolerability and preserves pharmacokinetics Ultrasound guidance is not something most people will encounter for a routine injection, but for patients on long-term depot medications who experience frequent site reactions, it is an option worth discussing with a provider.