How to inject testosterone — SubQ vs IM, technique, sites, and what to expect

If you're starting testosterone cypionate, you have one main choice to make about technique: subcutaneous (SubQ) or intramuscular (IM). Both are clinically valid. Both produce equivalent serum testosterone over a weekly cycle. They differ in needle size, depth, comfort, and a few small practical details that matter when you're the one doing it on a Tuesday morning in your kitchen.

This guide is what we walk every new TRT patient through. It covers what each injection actually is, how to do it, where to do it, and how to choose between them. It's educational — your physician confirms the right approach for you, watches your labs, and adjusts.

What is a subcutaneous (SubQ) injection?

A subcutaneous injection delivers medication into the fatty layer just beneath the skin, above the muscle. The needle is short (typically 5/16″ to 1/2″, a 27 to 30 gauge insulin-style needle), inserted at a 45° to 90° angle depending on body composition. Absorption from SubQ is slower than IM but steady; for a long-acting ester like cypionate the weekly serum profile is essentially the same.

SubQ is what insulin users have done at home for decades. Semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro, Zepbound), and most peptides are also subcutaneous. It's the most patient-friendly route — small needle, shallow depth, very tolerable.

How to do a SubQ injection (step by step)

1. Wash your hands. Soap and water, 20 seconds.
2. Lay your supplies out: the vial, an alcohol pad, a draw needle (typically 18g 1.5″ to pull the oil through quickly), a SubQ inject needle (27–30g, 5/16″–1/2″), a 1 mL Luer-Lok syringe, and a sharps container.
3. Wipe the vial top with the alcohol pad. Let it air dry.
4. Attach the draw needle to the syringe. Pull the plunger to the dose volume you'll inject (e.g., 0.25 mL for a 50 mg dose at 200 mg/mL; 0.5 mL for 100 mg). Push that air into the vial — equalizes pressure so the oil draws easily.
5. Invert the vial and draw your dose. Pull the plunger past the target by a hair, then push back to your exact dose. Tap any bubbles to the top and push them out.
6. Swap the draw needle for the SubQ inject needle. Twist off the draw needle (drop into sharps), twist on the fresh inject needle.
7. Choose your site. Most common SubQ sites for TRT: lower abdomen (2 inches from the navel), upper outer thigh, or the back-of-arm fat pad. Rotate sites each week.
8. Pinch about an inch of skin and fat at the chosen site to lift the fat layer off the muscle.
9. Wipe the site with a fresh alcohol pad. Let it air dry (don't blow on it).
10. Insert the needle at 45° (thinner patients) or 90° (more abdominal fat) through the pinched skin. Quick, smooth motion — hesitation is what hurts.
11. Push the plunger slowly and steadily. A 0.5 mL cypionate dose takes ~5–8 seconds.
12. Withdraw the needle at the same angle it went in.
13. Drop the syringe + needle into the sharps container. Don't recap.
14. Light pressure on the site with a clean tissue for 10–15 seconds. A small bead of blood is normal; a slow ooze is not.

Where to inject SubQ (sites + rotation)

• Lower abdomen — left or right of the navel, at least 2 inches away. Easy access, generous fat pad, low pain. Avoid stretch marks, scars, and the umbilicus itself.
• Upper outer thigh — top third of the front-outer thigh. Good for patients who don't carry abdominal fat or prefer not to inject there. Pinch and inject.
• Back of the upper arm — the triceps fat pad. Harder to self-administer (needs the off-hand); easier if a partner does it.
• Love handles — the side flank pinch. Works well but rotate religiously to avoid lipoatrophy with chronic same-site use.

Rotate sites week-to-week. Same site every week for a year creates fibrous tissue that absorbs unpredictably. Simple rotation: left abdomen → right abdomen → left thigh → right thigh → repeat.

What is an intramuscular (IM) injection?

An intramuscular injection delivers medication into the body of a muscle, below the subcutaneous fat layer. Longer needle (typically 1″ to 1.5″, 22 to 25 gauge), inserted at 90°, deep enough that the oil deposits into vascularized muscle tissue. Absorption is faster than SubQ — peak serum levels arrive earlier — but the cycle- average is the same for a long-acting ester.

IM is what older TRT clinical literature is built on. Most of the original cypionate dosing studies used IM. It's also the only route for some medications (HCG reconstituted from a kit, certain oil-suspended steroids), so even SubQ TRT patients sometimes do one IM injection.

How to do an IM injection (step by step)

1. Steps 1 through 6 are identical to the SubQ procedure above — wash hands, lay supplies, wipe vial, draw your dose, swap to the IM inject needle.
2. Choose your site. Most common IM sites for TRT: ventrogluteal (upper hip), vastus lateralis (outer thigh), or deltoid (shoulder muscle, smaller dose volumes only).
3. Locate the muscle landmarks. Don't pinch — for IM you're going through the fat into the muscle, so a pinch can pull the muscle away from the needle.
4. Wipe the site with a fresh alcohol pad. Air dry.
5. Insert the needle at a 90° angle with a quick, smooth motion. Bury it most of the way — the bevel needs to be in muscle, not fat.
6. Aspirate (optional, discussed below). Pull back lightly on the plunger for 1–2 seconds. If you see blood, withdraw, replace the needle, and choose a new site. If no blood, proceed. (Note: aspiration is no longer required by most clinical guidelines for the ventrogluteal site — your physician will tell you what they prefer.)
7. Push the plunger slowly and steadily. IM takes a bit longer to feel smooth — ~10–15 seconds for 0.5 mL.
8. Withdraw the needle at the same angle it went in. Pressure on the site for 15–30 seconds.
9. Drop into sharps container. Don't recap.

Where to inject IM (sites + landmarks)

• Ventrogluteal (upper hip) — the modern preferred IM site for TRT. Place the palm of the opposite hand on the greater trochanter (the bony bump on the side of the hip), index finger on the anterior superior iliac spine (the top of the hip bone you can feel in the front), middle finger arcing back along the iliac crest. The triangle between your fingers is the ventrogluteal site. Deep muscle, no major nerves or vessels. Very tolerable.
• Vastus lateralis (outer thigh) — middle third of the outer thigh, between the greater trochanter and the knee. Easy to self-administer because you can see the site. Larger needle needed (1.5″ for most patients).
• Deltoid (shoulder) — only for small volumes (≤1 mL). Two finger-widths below the acromion (the bony point of the shoulder), in the meaty body of the muscle. Often more painful than the lower-body sites; commonly skipped for TRT.
• Dorsogluteal (upper outer butt) — the traditional site, increasingly avoided in modern practice because of proximity to the sciatic nerve and superior gluteal artery. Ventrogluteal has largely replaced it.

Rotation matters here too. Switch between left and right ventrogluteal week to week. If you split the dose twice-weekly, alternate sides between doses.

SubQ vs IM — how to choose

Both routes produce essentially equivalent weekly-cycle serum testosterone with cypionate. The difference is comfort, ease, and a few clinical details:

• Pain and bruising: SubQ wins. Smaller needle, shallower depth. Most patients describe SubQ as “barely felt it” vs IM as “quick sting.”
• Ease of self-administration: SubQ wins — you can see the site (abdomen, thigh), the needle is short enough that hesitation doesn't cost you.
• Speed of onset: IM is slightly faster (hours instead of half a day to peak), but for weekly TRT this doesn't translate to a meaningful clinical difference.
• Clinical history: IM has decades of literature. SubQ is well-validated for cypionate but newer in clinical adoption; some traditional clinicians still default to IM.
• Estradiol management: Some clinicians and patients observe that SubQ may produce a slightly higher estradiol-to-testosterone ratio than IM for the same dose, because of slower oil-depot release and possibly different aromatase exposure in subcutaneous fat. The published data is mixed; if it matters for you, your follow-up labs will show it and the dose can be adjusted.

Most new TRT patients should start with SubQ. Lower-friction, easier learning curve, and you can switch to IM later if needed. If you're already doing IM and it's working, there's no clinical reason to switch.

Weekly vs twice-weekly dosing

For cypionate, both cadences work. Twice-weekly (half-doses Monday and Thursday, e.g.) produces a smoother serum profile — smaller peaks and shallower troughs across the week. Some patients feel the difference (more consistent energy, sleep, mood); some don't notice. The total weekly dose is the same.

Twice-weekly is doubly relevant if you're injecting SubQ and dose volume is small (0.25–0.5 mL per injection — easy to tolerate). For weekly IM injections at higher volume, the additional comfort is a real consideration.

What to expect the first few weeks

• Mild site soreness for 24–48 hours, especially with IM. A bit of warmth or redness at the site is normal. Spreading redness, increasing pain, or fever is not — call your physician.
• A small bead of blood on withdrawal is normal. Bruising at the site happens occasionally, especially with anticoagulant medications.
• “Crashing” (sudden fatigue 1–3 days post-injection) is unusual on cypionate at typical doses but reported. Often resolves once steady-state serum levels are established (week 4–6).
• Bumps under the skin (SubQ) — a small, painless lump that disappears within 24 hours is the oil depot. A persistent, hard, tender lump warrants a check-in.

Sterility, sharps disposal, and common mistakes

• One needle per injection. Never reuse the draw needle for injection (the bevel dulls and oil residue can introduce contamination). Never reuse the inject needle.
• Don't pre-load syringes more than a few hours ahead. Once oil is in the syringe, sterility starts to drift. Draw immediately before injection.
• Sharps container within arm's reach before you start. Drop used needles directly in — never recap, never set down on the counter.
• Refrigeration: cypionate is an oil-based preparation and lives at room temperature (no refrigeration needed). Store away from heat and direct sun. If a compounded preparation has a beyond-use date (BUD), respect it — don't use past expiration.
• If you crystallize or cloud: cold temperatures or older oil can sometimes precipitate. Warm the vial gently between your palms for 1–2 minutes; the oil should clear. If it doesn't, don't use it — call us for a replacement.

When to call your clinician

• Hot, spreading redness at the site, fever, chills, or pus — possible infection, needs same-day attention.
• Severe pain persisting beyond 72 hours.
• A red streak tracking from the injection site toward the heart — call urgent care; rare but serious.
• Sudden, severe headache, chest pain, or shortness of breath in the hours after an IM injection — extremely rare but possible if an air bubble or oil entered a vessel. Emergency care.
• Any persistent lump, color change, or mass at an injection site — check-in with the clinical team.

How we handle this at Vektor

Every new TRT patient gets a video walkthrough of their first injection with our nurse — SubQ or IM, whichever your physician has prescribed. We don't hand you a vial and expect you to figure it out from YouTube. Direct messaging is answered by a registered nurse in NYC; you can ask injection questions any time, not just at your scheduled visits.

The $99/mo retail (founders $89.10) covers everything the quarterly box needs — drug, supplies, shipping. Labs are separate at our pharmacy partner's actual cost ($88.25 TRT panel, blood draw included; no markup). The full pricing breakdown lives at /pricing; the TRT protocol detail is at /protocols/testosterone-cypionate.