Subcutaneous vs Intramuscular Testosterone: Which Injection Is Better?

Medically reviewed by: Katelyn Schwartz, NP, Family Nurse Practitioner with Advanced Training in TRT, BHRT, and Menopause Care
Last reviewed: November 2026

When comparing subcutaneous vs intramuscular testosterone injections, the finding cuts in both directions: both methods are clinically effective. The difference lies in absorption speed, hormone level stability between doses, and the practical experience of self-injection. Subcutaneous (SubQ) injection places testosterone in the fatty tissue beneath the skin; intramuscular (IM) injection targets muscle. Protocol design, anatomy, and individual response together determine the better fit.

How Testosterone Injections Work: What Both Methods Have in Common

Both SubQ and IM injections use an oil-based testosterone solution. The oil forms a depot at the injection site, and ester-linked testosterone leaves that depot gradually, enters surrounding tissue, and absorbs into the bloodstream. The ester controls how long the hormone stays active before clearance. This pharmacokinetic foundation is the same for both routes; what changes is how fast the depot releases.

Both routes also require regular lab monitoring. Therapeutic range confirmation, dose adjustments, and safety tracking all depend on consistent blood work, regardless of injection method. For an overview of available testosterone replacement therapy delivery options beyond injections, the Beyoung Health service page covers the full clinical picture.

Intramuscular Injections: How They Work, Site Options, and What to Expect

IM testosterone delivers the oil depot into dense, well-vascularized muscle tissue. Because muscle has high blood flow density, absorption is comparatively rapid. Testosterone typically peaks within one to two days post-injection, then declines until the next dose. On biweekly or less frequent schedules, the gap between peak and trough can become clinically noticeable.

Some patients describe this as a “peaks and valleys” pattern. Energy runs higher in the first few days after injection; then fatigue and mood dips arrive as levels fall before the next dose.

The ventrogluteal, dorsogluteal, and lateral thigh muscles are standard IM sites. The deltoid is used for smaller volumes. IM injections typically use a 21- to 23-gauge needle, one to 1.5 inches long, with volumes of 0.5 to 1.5 mL per injection. Reaching the gluteal site independently can be difficult for patients with limited flexibility or higher body fat; the lateral thigh is the practical alternative.

Testosterone Levels Fluctuate Naturally Over Time

Subcutaneous Injections: How They Work, Site Options, and What to Expect

SubQ injection deposits the oil into the fat layer just beneath the skin, typically at the abdomen or outer thigh. This tissue is less vascularized than muscle, so absorption is slower and more gradual. The result is a flatter hormone curve: a lower peak and a higher trough compared to the same dose given IM.

A small 2017 study in the Journal of the Endocrine Society followed 11 transgender men already stable on weekly SubQ testosterone. Researchers drew blood eight times across one week. Levels rose modestly in the hours after the injection. Even so, the average stayed within the normal range all week. The reading just before the next shot was also close to the one taken seven days earlier. That stability is the main clinical argument for SubQ on frequent-dosing protocols, although the study was small and did not include hypogonadal men.

The target layer sits 0.25 to 0.5 inches below the skin surface. SubQ needles are therefore shorter and finer: 25 to 27 gauge, up to five-eighths of an inch long. Volumes per injection are smaller as well, generally 0.2 to 0.5 mL, which reduces discomfort at each administration.

Key Differences: Peaks, Troughs, Hematocrit, and Estradiol

Choosing between subcutaneous vs intramuscular testosterone injections involves four parameters that differ between routes in ways that matter for long-term management.

Testosterone Peak and Trough

IM produces a sharper peak and steeper trough over the injection interval. SubQ produces a flatter curve for the same weekly dose. Patients on once-weekly IM near their trough may notice returning fatigue or mood shifts before the next injection. SubQ at twice-weekly intervals tends to keep levels more consistent across the dosing period.

The injection curve is only one reason energy can sag on treatment. Estradiol, iron stores, and sleep apnea can matter too, and our article on fatigue on TRT and how to fix it covers each one.

Hematocrit

Testosterone stimulates red blood cell production through erythropoietin signalling, and elevated peak concentrations amplify this effect. A 2022 Journal of Urology study found higher hematocrit after 12 weeks with IM testosterone than with SubQ testosterone delivered via autoinjector. The autoinjector was designed specifically to reduce peak concentration.

SubQ does not eliminate hematocrit elevation as a monitoring concern. However, its flatter peak may reduce the degree of rise in patients who are sensitive to this effect.

Estradiol

Testosterone aromatizes to estradiol at a rate that is partly concentration-dependent. Higher peaks produce greater aromatization in some patients. The 2022 Journal of Urology study found lower post-therapy estradiol levels in the SubQ group, consistent with its lower peak concentration.

Estradiol varies widely between individuals on both routes. Lab monitoring, not route selection, is the primary management tool.

Local Reactions

SubQ injections occasionally produce small nodules at the injection site. This typically occurs when volume is too large for the site or depth is inconsistent. These reactions resolve without treatment in most cases. Rotating sites and keeping volumes within the SubQ range minimizes their frequency. IM carries its own risk of scar tissue with repetitive use of the same site; rotation applies equally to both methods.

Practical Comparison: Frequency, Volume, Needle Size, and Self-Injection Ease

The table below brings the differences from the sections above into one place. The ranges are typical ones, and your own protocol may differ.

Feature	Intramuscular (IM)	Subcutaneous (SubQ)
Where the oil goes	Into muscle: glute, outer thigh, sometimes the shoulder	Into the fat layer under the skin: abdomen or outer thigh
Injection depth	1–1.5 inches	0.25–0.5 inches
Typical needle	21–23 gauge, 1–1.5 inches long	25–27 gauge, up to 5/8 inch long
Volume per injection	0.5–1.5 mL	0.2–0.5 mL
Usual frequency	Weekly or every two weeks	Weekly, sometimes split into two smaller shots
Peak and dip	Peaks in the first days after the shot, then falls until the next dose	Tends to rise more gently and stay flatter across the week
Hematocrit	Higher after 12 weeks in a 2022 comparison study	Lower in that study; regular checks are still needed
Estradiol	Higher on average in the same study	Lower on average, though individual results vary widely
Comfort	Thicker, longer needle and more oil; the muscle may ache for a day or so	Finer needle and less oil; often described as less painful, with small lumps possible
Self-injection	The glute is hard to reach alone; the outer thigh is the usual home site	The abdomen is easy to see, pinch and inject

The finer SubQ gauge reduces discomfort per injection. The shallower depth requires less precision. Because SubQ volume is smaller, SubQ protocols typically divide the weekly dose across two or more injections rather than a single larger shot. The abdominal site also provides direct visual feedback that most gluteal IM sites do not.

For the factors that influence injection interval decisions, the article on how often to inject testosterone covers them in detail.

Which Injection Hurts Less?

For most men starting TRT, the first worry isn’t peaks or hematocrit. It’s whether the shot will hurt, and whether they can face doing it themselves every week. On that question, the evidence on subcutaneous vs intramuscular testosterone leans toward SubQ. Still, the reason matters more than the route.

Needle Size and Volume Drive Most of the Pain

Two things decide most of the sting: how wide the needle is and how much oil goes in. SubQ shots usually use a 25- to 27-gauge needle, while IM shots use 21 to 23 gauge. Gauge numbers run backwards, so a higher number means a thinner needle and a smaller puncture.

Volume matters just as much. Testosterone oil is thick, and pushing 1 mL or more into one spot stretches the tissue around it. That pressure likely accounts for some of the next-day ache. Because SubQ doses usually sit between 0.2 and 0.5 mL, there is simply less oil to make room for.

What Patients and Studies Report

A 2017 study in the Journal of Clinical Endocrinology and Metabolism followed 63 transgender men on weekly SubQ testosterone. Of these, 22 had switched from IM shots. All 22 preferred SubQ, and 20 called the preference marked. Similarly, in a 52-week study of 150 hypogonadal men using a weekly SubQ autoinjector, more than 95% reported no injection-related pain.

A 2022 review in the same journal concluded that, with training, patients should be able to self-inject SubQ with relative ease and less discomfort than IM. Still, neither study randomly compared the two routes, and the autoinjector study had no comparison group. These are strong signals, not settled proof.

When Subcutaneous Injections Can Hurt More

Comfort depends on keeping SubQ doses small. A 2019 crossover trial in the Journal of the Endocrine Society tested this in 20 men. Each received a large 4 mL dose of a long-acting testosterone form both ways, with a 21-gauge needle for each route. Pain right after the shot was similar. However, SubQ hurt more 24 hours later, and 11 of the 20 men preferred IM. In other words, the SubQ advantage comes from fine needles and small volumes, not from the fat layer itself.

Common Mistakes With Subcutaneous and Intramuscular Injections

Many injection problems come from technique rather than from the route itself. These four come up often, and each one is easy to fix once you know it.

Using the wrong angle. SubQ shots usually go into a pinched fold of skin at 45 or 90 degrees. The right angle depends on how much fat sits at the site. IM shots go straight in at 90 degrees. A shallow IM shot can leave oil in fat, while a steep SubQ shot in a lean area can reach muscle. Ask your provider or pharmacist to check your angle for your body and site.
Pushing the plunger too fast. Thick oil needs time to spread. A fast push raises pressure in the tissue, which can cause stinging, leakage and lumps afterwards. A slow, steady push is gentler on both routes.
Reusing the same spot. Repeated shots in one area can leave firm patches under the skin or scar tissue in the muscle. They may also change how evenly the dose absorbs. Instead, rotate between sides and move each new SubQ shot about an inch from the last.
Ignoring lumps that change. A small, painless bump after a SubQ shot is common and usually fades within days. On the other hand, a lump that grows, turns red and hot, or drains needs a same-day call to your provider. So does any lump with a fever.

Who Might Prefer Subcutaneous and Who Might Prefer Intramuscular

SubQ vs IM testosterone: which is better? There is no universal answer. Both methods produce comparable average testosterone levels in the studies so far when dose and frequency are appropriately matched.

SubQ may be worth discussing with a licensed nurse practitioner if you:

Inject twice weekly or more frequently and prefer a finer needle and smaller volume
Have difficulty reaching the gluteal site independently due to anatomy or flexibility
Show elevated hematocrit or estradiol on IM and want to explore a flatter absorption profile
Find the abdominal injection site easier to control during self-administration

IM may remain the preferred choice if you:

Use a once-weekly or biweekly protocol with larger injection volumes
Tolerate IM well without significant symptom fluctuation between doses
Prefer the higher post-injection peak pattern in the first days after injection

Route selection is a clinical decision that belongs to the patient and their licensed provider. The overview of testosterone replacement therapy methods and approaches covers how different delivery formats are evaluated clinically.

How Canadian TRT Protocols Shape the Choice

In Canada, injectable testosterone is typically given into the muscle. The Canadian Urological Association guideline lists a weekly schedule as a standard option alongside an injection every two weeks. In practice, many Canadian protocols now favour the weekly pattern because it keeps levels steadier.

That detail matters for route choice. Once you inject every week, each dose is smaller, so it fits comfortably under the skin. A two-week schedule, by contrast, usually means a larger dose that suits muscle better. Either way, choosing SubQ is a decision you make with your provider. It rests on your labs and on how you manage injections at home. If you live in British Columbia, our TRT in Vancouver program sets the schedule, the route and the follow-up labs as one plan.

How to Switch Between Subcutaneous and Intramuscular Injections

Patients usually raise a switch for one of three reasons: IM shots hurt, reaching the glute alone is awkward, or hematocrit keeps creeping up. Whatever the reason, the change works best as a planned step with your provider, not a mid-cycle experiment.

Step 1: Agree on the Plan Before the Next Dose

Your provider should confirm the new site, the needle, the schedule and the date of your next blood test. If you have only injected into muscle so far, ask for a short technique review first. The angle and the pinch are different under the skin.

Step 2: Dose and Frequency

Studies so far suggest that the same weekly amount gives similar average levels by either route. For that reason, many providers keep the weekly total unchanged and change only the route. Sometimes the same total is spread across two smaller shots, with the amount per shot set by your provider. If you currently inject every two weeks, a switch to SubQ often means moving to weekly shots at the same time. That’s because SubQ volumes are small. Never adjust the amount on your own.

Step 3: Recheck Your Labs

Plan on a testosterone level and a hematocrit within the first few months after the change. The Canadian Urological Association schedule checks both about three months after treatment starts, then continues regular monitoring. Many providers use a similar timeline after a route change. For injections, the blood draw is usually timed mid-cycle, so book it on the day your provider gives you. Our guide to TRT blood tests explains what each marker shows.

Step 4: Watch for Early Warning Signs

Tell your provider if energy or mood starts dipping before each shot, or if an injection site lump grows, turns hot or drains. Calf pain or swelling, chest pain or sudden shortness of breath are different: go to an emergency department or call 911 right away.

Common Questions and Misconceptions

“SubQ doesn’t work as well because it’s not going into the muscle.” Both routes release testosterone from the same oil depot into the bloodstream. Subcutaneous vs intramuscular testosterone comparisons show similar average hormone levels; what differs is absorption kinetics, not efficacy. A 2022 review in the Journal of Clinical Endocrinology and Metabolism found that SubQ doses similar to IM doses produce comparable average testosterone levels, while noting that the evidence is still limited.

“IM gives bigger muscle gains on TRT.” At therapeutic doses, the delivery method does not determine muscle response. Androgenic effects result from testosterone binding to androgen receptors in muscle tissue regardless of how the hormone entered circulation.

“SubQ is experimental.” It is a newer routine option than IM, but it is not experimental. Published studies in hypogonadal men and transgender patients have used it for years. In fact, a 2022 review in the Endocrine Society’s own journal encouraged providers to discuss it with their patients.

Frequently Asked Questions

Q: Is subcutaneous testosterone as effective as intramuscular?

For most people, the evidence so far points that way. In studies of hypogonadal men and transgender patients, SubQ shots at weekly amounts similar to IM brought testosterone into the normal range. Average levels were comparable. What differs is the shape of the curve, since SubQ gives a lower peak and a steadier week. The research is still smaller than for IM, so your labs confirm whether your protocol is working.

Q: Which injection hurts less?

Many patients find SubQ less painful, because it uses a finer 25- to 27-gauge needle and a smaller volume than IM. In one study, all 22 patients who moved from IM to SubQ preferred SubQ. The advantage depends on keeping volumes small, though. In another trial, a large 4 mL dose under the skin hurt more the next day than the same dose in muscle.

Q: Does subcutaneous injection cause more lumps or reactions?

Nodules can occur when injection volume is too large or depth is inconsistent. They are generally temporary and resolve within a few days. Rotating injection sites and keeping volumes within the appropriate SubQ range minimizes their frequency. IM also carries a risk of localized scar tissue with repetitive use of the same site.

Q: Which injection method is easier to do at home?

SubQ is generally considered easier by most patients who have tried both. The abdominal site is easy to see and reach. The shorter needle requires less depth precision, and a smaller volume reduces resistance during injection. Some patients find a well-practiced IM technique equally manageable after adequate training.

Q: Can I switch methods?

Yes, but plan the switch with your provider rather than changing on your own. Many providers keep the same weekly total and change only the route. Sometimes that total is spread across two smaller shots, with the amount per shot set by the provider. Expect repeat testosterone and hematocrit checks in the months after the switch, drawn at the point in your cycle your provider specifies.

Q: Does subcutaneous testosterone raise hematocrit less?

It may. A 2022 Journal of Urology study followed 234 men on weekly treatment. After adjusting for other factors, the group using a SubQ autoinjector had lower hematocrit and estradiol at 12 weeks than the IM group. The two groups also used different testosterone preparations, so the route was not the only difference. Either way, SubQ does not remove the need for regular hematocrit checks.

The evidence on subcutaneous vs intramuscular testosterone injections supports both methods when correctly managed. Beyoung Health provides online assessment and lab requisitions through licensed nurse practitioners. Lab testing is required before any prescription is issued, and follow-up requisitions are included in the ongoing care plan.

This content is for informational purposes only and does not constitute medical advice. Consult a licensed provider before starting, adjusting, or stopping any hormone therapy.