The four intramuscular testosterone labels reviewed here from the Food and Drug Administration (FDA) name only the gluteal muscle. The single subcutaneous product names the abdominal region alone. The thigh and deltoid appear in vaccine guidance and anatomy studies, not on the labels.
No clinical trial evaluating testosterone esters across different intramuscular sites was located. What exists instead is anatomy and nursing research on other injected drugs. Fat thickness over the buttock varies substantially between individuals. Fat depth is greater in women and at the dorsogluteal site.
The Verdict
What the Labels Name as the Injection Site
United States prescribing labels limit intramuscular testosterone to the gluteal muscle and subcutaneous formulations to the abdomen. The Pfizer label for Depo-Testosterone specifies that injections must be administered deep in the gluteal muscle. It provides a dosage range of 50 to 400 mg every two to four weeks. The text contains no reference to the thigh, deltoid, or ventrogluteal area. It provides no needle dimensions and gives no instruction on site rotation.
The generic DailyMed label for testosterone enanthate directs administration deeply into the gluteal muscle. Like cypionate, it omits the thigh entirely. The label for AZMIRO requires deep gluteal intramuscular administration at a 90-degree angle. Its packaging does not include a needle.
Only two branded labels introduce anatomical specificity or site variation. The AVEED label identifies the gluteus medius in the upper outer quadrant of the buttock. It directs administrators to avoid the superior gluteal arteries and sciatic nerve. It also instructs administrators to alternate between the left and right buttock between consecutive injections. The subcutaneous formulation XYOSTED specifies subcutaneous injection in the abdominal region only. It explicitly directs users to avoid intramuscular or intravascular administration.
| Product | Route | Labeled Site | Labeled volume or strength |
|---|---|---|---|
| Depo-Testosterone (cypionate) | Intramuscular | Deep gluteal muscle | 100 mg/mL or 200 mg/mL (volume not stated) |
| Testosterone enanthate (generic) | Intramuscular | Deep gluteal muscle | Not stated in facts reviewed |
| AZMIRO (cypionate) | Intramuscular | Deep gluteal muscle | 1 mL prefilled syringe or vial |
| AVEED (undecanoate) | Intramuscular | Gluteus medius muscle | 3 mL |
| XYOSTED (enanthate) | Subcutaneous | Abdominal region only | 0.5 mL autoinjector |
The Verified Absence of Head-to-Head Site Trials
No head-to-head trial comparing different intramuscular injection sites using a testosterone ester was located. No study evaluating serum testosterone levels or tolerability differences between gluteal and thigh injections was located. No label ranks one intramuscular location against another.
Discussions comparing injection sites draw entirely on anatomy studies, imaging reviews, or trials evaluating non-hormonal medications. Those investigations measure tissue thickness, vascular hazards, and patient-reported discomfort from injections of other drugs. Applying those conclusions to oil-based testosterone depots involves clinical inference rather than direct evidence. Our guide to TRT injections, cream, and pellets outlines how absorption profiles vary across wider delivery methods.
Dorsogluteal and Ventrogluteal Sites in the Sciatic Injury and Pain Literature
Anatomical research differentiates between two primary gluteal regions. The literature compares dorsogluteal and ventrogluteal injection sites. A 2004 review in the Journal of Advanced Nursing associated sciatic nerve injury specifically with the dorsogluteal site. The author noted broad professional agreement favoring the ventrogluteal location, while emphasizing that the overall research base remained limited.
Complication records report this anatomical hazard. A clinical series in Turkish Neurosurgery reviewed 217 patients diagnosed with injection-related sciatic nerve injury. Every single case involved dorsogluteal administration. Non-steroidal anti-inflammatory drugs represented the most common injected compounds. Significant sequelae remained in two thirds of cases on follow-up electromyography (103 patients). The study did not include testosterone injections.
Clinical trials comparing discomfort between these locations present mixed results. A 2023 meta-analysis in Nursing Open across 17 studies found that ventrogluteal administration reduced pain compared to dorsogluteal injections. It found no significant difference in the likelihood of inadvertently depositing medication into subcutaneous tissue. A 2021 review in PLOS ONE similarly documented lower pain scores at the ventrogluteal site. However, the study authors identified substantial unexplained heterogeneity and considerable risk of bias among the published data.
Tissue Depth and Needle Penetration Across Gluteal Sites
Imaging trials show that standard needles do not reach gluteal muscle in a considerable number of patients. A 2023 meta-analysis in the Journal of Research in Nursing evaluated ultrasound measurements across 734 adults. Pooled measurements by the V method showed ventrogluteal muscle thickness of 38.071 ± 2.119 mm and subcutaneous tissue of 19.927 ± 2.493 mm. Subcutaneous tissue was thicker in women (p = 0.0204), with no effect of BMI on ventrogluteal subcutaneous thickness.
Similar findings appear in individual ultrasound trials. An evaluation of 145 adults published in the Journal of Clinical Nursing found that subcutaneous fat and muscle were thicker at the dorsogluteal site than the ventrogluteal site. The authors predicted successful intramuscular penetration in 75% of dorsogluteal attempts and 86% of ventrogluteal attempts. They projected that a 32 mm needle at the ventrogluteal site would succeed for all males and normal-weight females, but noted both gluteal sites should be avoided in obese and endomorph individuals. This is the authors' injection-geometry conclusion; no testosterone label specifies a needle.
Computed tomography and magnetic resonance imaging show comparable penetration challenges. A computed tomography trial in the BMJ evaluated 100 adults. Fat depth averaged 19.0 mm at the ventrogluteal site and 32.0 mm at the dorsogluteal site. Dorsogluteal fat thickness exceeded 25 mm in 44% of men and 90% of women.
An imaging trial in the American Journal of Therapeutics examined 350 adults using magnetic resonance imaging. Fat thickness correlated closely with body mass index. The investigators projected that a 3.75 cm needle would fail in 71% of women with a body mass index above 30 and 60% of men with a body mass index above 35. A computed tomography evaluation of 568 Korean adults by Joo and Sohng reported gluteal subcutaneous fat thickness of 15.92 ± 4.08 mm in men and 24.90 ± 5.47 mm in women, exceeding 20.4 mm in 12.3% of 440 men and 77.3% of 128 women.
| Study | Imaging Method | Site Evaluated | Primary Tissue Findings |
|---|---|---|---|
| Gulnar et al. (2023) | Ultrasound (734 adults) | Ventrogluteal | Pooled mean by V method: muscle 38.071 mm, subcutaneous fat 19.927 mm; no BMI effect |
| Larkin et al. | Ultrasound (145 adults) | Dorsogluteal vs ventrogluteal | Successful muscle penetration predicted in 75% dorsogluteal vs 86% ventrogluteal |
| BMJ CT Study (2006) | Computed tomography (100 adults) | Dorsogluteal vs ventrogluteal | Mean depth 32.0 mm dorsogluteal vs 19.0 mm ventrogluteal; depth exceeded 25 mm in 44% of men at dorsogluteal site |
| Holliday et al. | Magnetic resonance imaging (350 adults) | Ventral gluteal | 3.75 cm needle projected to fail in 71% of women with BMI > 30 and 60% of men with BMI > 35 |
| Joo and Sohng | Computed tomography (568 adults) | Gluteal region | Mean fat 15.92 mm in men, 24.90 mm in women; exceeded 20.4 mm in 12.3% of men and 77.3% of women |
Body Weight and Serum Concentrations on Testosterone Undecanoate
Clinical trials of testosterone undecanoate demonstrate an inverse correlation between patient body weight and circulating hormone levels. Prescribing documentation for AVEED indicates that total testosterone concentrations were lower in heavier individuals throughout an 84-week study. Men weighing 100 kg or more maintained an average concentration of 426 ng/dL. Men weighing between 65 and 100 kg averaged 568 ng/dL.
The trial documented a parallel disparity across body mass index categories. Participants with a body mass index above 30 recorded average concentrations of 445 ng/dL. Men with an index below 26 achieved average levels of 579 ng/dL. Those with an index between 26 and 30 averaged 567 ng/dL.
The AVEED label reports these statistical differences without identifying a biological cause. The document does not link the finding to tissue depth, needle length, or inadvertent subcutaneous deposition. Those imaging observations and pharmacokinetic figures remain separate data points in published literature. Our analysis of TRT side effects and risks outlines broader physiological factors that shift systemic response.
Thigh and Shoulder Sites in Vaccine and Anatomy Research
Published data regarding intramuscular thigh and deltoid injections come from vaccine guidance and soft-tissue imaging. An ultrasound study of 54 obese adults in the Journal of Ultrasound in Medicine measured subcutaneous tissue across three anatomical locations. Depths averaged 61.70 mm at the dorsogluteal site, 27.05 mm at the rectus femoris, and 23.23 mm at the vastus lateralis. The authors concluded that a standard needle at the thigh reached muscle in all men and 77.8% of women in the rectus femoris and vastus lateralis.
A combined ultrasound and cadaver study in Human Vaccines & Immunotherapeutics evaluated the vastus lateralis. The authors identified the middle of the vastus lateralis as suitable for intramuscular delivery due to low vascular and nerve injury risks. General vaccine guidelines from the Centers for Disease Control and Prevention (CDC) identify only two adult intramuscular sites. Those locations are the deltoid muscle in the upper arm and the vastus lateralis in the anterolateral thigh.
The CDC intramuscular injection reference specifies needle lengths for adults based on body weight. It recommends a 1-inch needle for individuals under 70 kg and a 1- to 1.5-inch needle for men weighing 70 to 118 kg. It reserves 1.5-inch needles for men over 118 kg. These recommendations apply to vaccines. No testosterone label names the thigh or deltoid for cypionate or enanthate.
Subcutaneous Injection in the Abdomen
The abdominal wall provides the sole approved location for subcutaneous testosterone enanthate. In a phase II trial published in Sexual Medicine, 39 men received weekly subcutaneous enanthate doses of 50 mg or 100 mg using a 27-gauge, five-eighths-inch needle. Steady-state testosterone reached 422.4 ng/dL and 895.5 ng/dL respectively. The trial compared those groups against a separate cohort receiving 200 mg of intramuscular enanthate. Because the doses differed, the trial did not establish an equivalent bioavailability comparison.
A 52-week registration study in The Journal of Urology followed 150 men using the 75 mg subcutaneous autoinjector. By week 12, 92.7% of participants achieved total testosterone concentrations between 300 and 1,100 ng/dL. Our review of testosterone injection pain examines local tissue reactions and tolerability.
Clinical trials comparing subcutaneous and intramuscular delivery often introduce confounding variables. A 2022 study in The Journal of Urology compared 234 men receiving weekly intramuscular cypionate or subcutaneous enanthate. Subcutaneous use was independently associated with lower hematocrit, but route and ester changed together (intramuscular cypionate versus subcutaneous enanthate autoinjector), so the finding cannot be assigned to the injection site alone. Our analysis of high hematocrit on TRT details the erythrocytic response.
A study in the Journal of the Endocrine Society evaluated weekly subcutaneous cypionate in 11 female-to-male transgender patients (mean total testosterone 627 ± 206 ng/dL), though the study did not evaluate hypogonadal men. A 2021 review by Figueiredo, Gagliano-Jucá, and Basaria in The Journal of Clinical Endocrinology & Metabolism describes administering subcutaneous testosterone 3 to 5 cm lateral to the umbilicus or in the thigh, noting from clinical experience that a 23-gauge needle can be used without difficulty. The XYOSTED label specifies the abdominal region only; the review describes practice with other subcutaneous esters.
Injection Site Rotation Across Prescribing Instructions
Of the five labels reviewed here, only AVEED instructs alternating injection sites. The single exception among injectable testosterone products is AVEED. Its label directs administrators to alternate the injection site between the left and right buttock between consecutive procedures.
The labels for Depo-Testosterone, generic testosterone enanthate, and XYOSTED contain no instructions to alternate sides or rotate puncture sites.
Who This Evidence Does Not Serve
Label instructions do not address men seeking approved alternative intramuscular sites. Prescribing documents name only the gluteal muscle for intramuscular products and the abdomen for subcutaneous delivery. Any comparison between intramuscular sites relies on non-hormonal anatomical inference rather than direct clinical evidence.
A formal trial evaluating serum concentrations, pain scores, and adverse events across different intramuscular sites using identical testosterone esters would alter this reading of the literature. A label revision expanding approved administration points for cypionate or enanthate would similarly change the regulatory position. Until those trials occur, differences between anatomical regions remain derived from non-hormonal studies.
Frequently Asked Questions
Where is testosterone cypionate injected?
The official FDA prescribing labels for testosterone cypionate specify that injections must be administered deep in the gluteal muscle of the buttock. This requirement appears on both the Pfizer Depo-Testosterone label and the AZMIRO label. The approved package inserts make no mention of the thigh, shoulder, or any secondary intramuscular sites. They do not include instructions for subcutaneous administration. While clinicians sometimes discuss alternative injection locations in clinical literature, the gluteal muscle remains the single approved anatomical site described in current US prescribing documentation.
Is testosterone injected in the glute or the thigh?
Approved drug labels for intramuscular testosterone formulations specify only the gluteal muscle. Depo-Testosterone, generic testosterone enanthate, AZMIRO, and AVEED all restrict intramuscular administration to the buttock. No approved testosterone label names the vastus lateralis or any other thigh muscle. References to thigh injections come from soft-tissue imaging trials, vaccine protocols, and reviews of other subcutaneous regimens. In published imaging studies, fat thickness over the thigh was thinner than the gluteal area in obese cohorts, but no testosterone label names the thigh for cypionate or enanthate.
Does the label say to inject testosterone in the thigh?
None of the five FDA prescribing labels reviewed here mentions the thigh as an approved injection site. The labels for Depo-Testosterone and generic enanthate specify deep gluteal injection only. The subcutaneous formulation XYOSTED explicitly restricts administration to the abdominal region. Guidance suggesting the thigh originates in vaccine administration standards published by the Centers for Disease Control and Prevention or in independent clinical commentary.
Where is Xyosted injected?
The prescribing label for XYOSTED directs users to inject the drug subcutaneously into the abdominal region only. The instructions explicitly warn against administering the medication intramuscularly or intravascularly. In its 52-week clinical registration trial of 150 men, weekly abdominal administration with the single-dose autoinjector maintained total testosterone levels between 300 and 1,100 ng/dL in 92.7% of patients. Although general medical reviews sometimes discuss administering subcutaneous testosterone into the thigh, the approved manufacturer label restricts use entirely to the abdomen.
Where is AVEED injected, and why does the label name the gluteus medius?
The AVEED prescribing label specifies that the 3 mL injection must be administered into the gluteus medius muscle, located in the upper outer quadrant of the buttock. The label directs that care must be taken to avoid hitting the superior gluteal arteries and the sciatic nerve during administration. It also instructs administrators to alternate between the left and right buttock between consecutive procedures. The label does not state why it names this specific muscle.
What is the difference between the ventrogluteal and dorsogluteal sites?
Anatomical reviews differentiate between the dorsogluteal site and the ventrogluteal site. Nursing research notes broad agreement favoring the ventrogluteal site to reduce sciatic nerve injury. Imaging trials also demonstrate that subcutaneous fat is thinner over the ventrogluteal area than the dorsogluteal area. Two meta-analyses, a 2023 review of 17 studies and a 2021 review of 29, found ventrogluteal injection associated with less pain than dorsogluteal injection, though the 2021 authors reported very high unexplained heterogeneity and a risk of significant bias within small studies.
Can an injection land in fat instead of muscle?
Yes. Published imaging studies show that subcutaneous fat thickness over the buttock frequently exceeds standard needle lengths. A 2006 computed tomography study in the BMJ found that skin-to-muscle depth exceeded 25 mm in 44% of men and 90% of women at the dorsogluteal site. An MRI study in the American Journal of Therapeutics projected that a 3.75 cm needle would fail to reach muscle in 71% of women with a body mass index over 30 and 60% of men over 35. In a published review of imaging studies, authors estimated that 12% to 85% of intended intramuscular injections administered to men were actually subcutaneous.
Does injection site rotation appear on testosterone labels?
AVEED is the only injectable testosterone formulation that instructs users to rotate injection sites. Its label explicitly directs administrators to alternate the injection between the left and right buttock between consecutive doses. The labels for Depo-Testosterone, generic testosterone enanthate, and XYOSTED contain no instructions regarding site rotation.
Is subcutaneous testosterone absorbed differently from intramuscular?
A review by Figueiredo et al. notes that subcutaneous tissue is less vascularized than skeletal muscle, inferring more stable vascular absorption patterns. In a phase II trial, subcutaneous testosterone enanthate autoinjectors restored normal testosterone levels relative to 200 mg intramuscular enanthate, though doses differed between arms. The authors also report that in an enanthate study, bioavailability was similar irrespective of route at steady state.