Testosterone Injections for Men — A Complete UK Guide to Injectable TRT

How to inject Testosterone

Intramuscular (IM) Injection — Step-by-Step

Intramuscular injection delivers testosterone directly into muscle tissue. It is the licensed route for all UK injectable testosterone products. Nebido (4 ml) must be administered by a healthcare professional and is not suitable for home self-injection.

Needle: 21G to 23G, 25 mm (1 inch) for most men; 38 mm (1.5 inch) for those with greater subcutaneous tissue depth over the injection site. Your clinic nurse will confirm the appropriate length at your training session.

Choosing an Injection Site

• Vastus lateralis (outer thigh) — the recommended site for self-administered IM injection. Use the middle third of the outer aspect of the thigh. A large, accessible muscle with no major neurovascular structures near the surface.
• Ventrogluteal (hip) — considered the safest IM site overall, with the lowest risk of nerve or vessel involvement. Requires correct anatomical landmarking but is achievable with practice. Suitable for self-injection in men with adequate flexibility.
• Dorsogluteal (upper outer buttock) — the traditional site, but increasingly not recommended due to the proximity of the sciatic nerve if positioned incorrectly. It is also difficult to access for self-injection. The ventrogluteal site is the preferred alternative.
• Deltoid (shoulder) — acceptable only for volumes of 1 ml or less. Not a primary site for TRT injections.

1. Wash your hands thoroughly with soap and water for at least 20 seconds and dry them on a clean towel.
2. Set out equipment on a clean, alcohol-wiped surface. Open the packaging and attach the drawing-up needle to the syringe.
3. Clean the ampoule neck or vial bung with an alcohol swab and allow to air dry fully.
4. Draw up the prescribed volume. For glass ampoules: snap the neck at the score point (use a snap ring or gauze to protect your fingers), insert the drawing-up needle and withdraw the medication. Draw up marginally more than required, then expel to the correct volume to remove any air.
5. Replace the drawing-up needle with the injecting needle. Hold the syringe upright, tap gently to move any bubbles to the top, and advance the plunger slowly until a small drop of oil appears at the tip, confirming the syringe is air-free.
6. Clean the chosen IM injection site with an alcohol swab. Allow to dry fully — approximately 30 seconds. Injecting through wet alcohol causes unnecessary stinging.
7. Z-track technique: with the non-dominant hand, pull the skin and subcutaneous tissue approximately 1–2 cm sideways, away from the intended needle entry point. Maintain this displacement throughout the injection. When the skin is released after the needle is withdrawn, the displaced tissue seals the needle track, keeping medication within the muscle and reducing injection site reactions.
8. While holding the displaced skin, insert the needle firmly and swiftly at 90 degrees to the skin surface.
   Inject slowly and steadily over 20 to 30 seconds. Slow injection of oil-based medication is essential — rapid injection is the most common cause of significant injection site pain.
9. After completing the injection, pause for approximately 10 seconds before withdrawing. This allows pressure to equalise and reduces medication tracking back up the needle path.
10. Withdraw the needle at 90 degrees in a single smooth motion. Release the displaced skin — the Z-track seals the deposit within the muscle.
11. Apply gentle pressure with sterile gauze. Do not massage the site.
12. Dispose of all sharps immediately in the sharps bin.

Tips for Reducing Injection Discomfort

• Bring the medication to room temperature before injecting. Cold oil is more viscous, flows through the needle with greater resistance, and is more uncomfortable. Hold the ampoule or vial in your hands for a few minutes beforehand.
• Ensure the alcohol swab has dried completely before the needle enters the skin.
• Use a fresh needle for every injection. Even a single pass through a rubber vial bung reduces needle sharpness significantly.
• Keep the muscle as relaxed as possible. For thigh injections, sit with the leg hanging freely rather than tense.
• Inject slowly. This is the single most effective measure for reducing pain.
• Rotate injection sites systematically and record which site was used each time.
• A warm compress applied to the site for five to ten minutes after injection encourages oil dispersion and reduces local soreness.

Opening Glass Ampoules

Testosterone enanthate and Sustanon 250 are supplied in glass ampoules. To open safely:

1. Tap the top of the ampoule to ensure all medication settles in the lower section.
2. Locate the score mark or coloured dot on the neck — this is the intended break point.
3. Use an ampoule snap ring or a small square of gauze to protect your fingers.
4. Hold the lower section firmly and snap the neck away from you at the score point.
5. Dispose of glass ampoule fragments in the sharps bin — not household waste.

Sharps Disposal

Used needles, syringes, and glass ampoule fragments are clinical waste and must be disposed of safely. Incorrect disposal is an offence under the Environmental Protection Act 1990.

• All used sharps must go immediately into an approved sharps container — yellow lid, BS EN ISO 23907 compliant. These are available on NHS FP10 prescription or from The Health Suite.
• Seal the bin when it is three-quarters full. Never overfill.
• Contact your local council for a sharps collection point or door-to-door clinical waste service — most UK councils provide this at no charge.
• Community pharmacies may accept sealed sharps bins for disposal.
• Never place sharps in household bins or recycling.

Dosing, Frequency, Missed Doses, and Travel

Starting Dose and Titration

For testosterone enanthate and cypionate, treatment typically begins at a conservative dose of 62.5 to 125 mg per week, increasing to the minimum dose that achieves symptom relief and a trough serum testosterone in the mid-normal physiological range (generally 15–30 nmol/L). Dose adjustments are made incrementally on the basis of blood results and symptom review, with re-testing four to six weeks after any change. Your prescribing doctor will set and review your dose — do not adjust it independently.

Injection Frequency

More frequent, smaller doses produce more stable hormone levels and reduce the magnitude of post-injection peaks, which lowers the erythropoietic stimulus and risk of haematocrit elevation. For testosterone enanthate and cypionate, twice-weekly injections of half the weekly dose are increasingly preferred over single weekly administration for this reason. Your individual frequency will be agreed at your prescribing consultation and reviewed based on blood results and symptoms.

Missed Dose

If a dose is missed, administer it as soon as it is noticed, provided it is still the same day. If it is the following day and the next scheduled injection is not for several days, administer the missed dose and resume the normal schedule. If the next injection is due shortly, omit the missed dose and continue as planned. Do not double-dose. If uncertain, contact The Health Suite for guidance.

Storage

• Store at room temperature, below 25–30°C depending on the product (confirm in the Summary of Product Characteristics for your specific medication). Protect from direct light.
• Do not refrigerate or freeze injectable testosterone — cold oil becomes unacceptably viscous and the medication may precipitate.
• Multi-dose vials (testosterone cypionate) must be discarded 28 days after first puncture, regardless of remaining volume.
• Inspect for cloudiness, discolouration, or particles before each use. If in doubt, do not use.
• Store out of the reach of children.

Travelling with Injectable Testosterone

Testosterone is classified as a Schedule 4 Part II Controlled Drug under the Misuse of Drugs Regulations 2001. When travelling — particularly abroad — the following precautions are necessary:

• Carry a letter from your prescribing doctor on clinic-headed notepaper, confirming your diagnosis, prescribed medication, dose, and frequency. Include the doctor’s GMC number. The Health Suite can provide this on request.
• Travel with original pharmacy-labelled packaging and a copy of the prescription where possible.
• Carry all injectable medication, needles, and syringes in hand luggage — not checked baggage — to avoid temperature extremes in the hold and the risk of loss.
• Prescription medications are exempt from the 100 ml cabin liquid restriction. A prescriber letter is usually sufficient at UK security.
• For international travel, check the destination country’s regulations on importation of Schedule 4 controlled drugs before departure. Some countries require advance authorisation from their national drugs authority. The Home Office issues a personal export/import licence for up to three months’ supply — contact the clinic if this is required.

Side Effects — What to Expect and What to Report

Injectable testosterone shares the same systemic side effect profile as other forms of TRT, with the addition of injection site-specific effects. The following covers what to expect in practice. Full side effect information is provided in the Summary of Product Characteristics for your product.

Injection Site Reactions

• Pain, redness, swelling, and warmth at the injection site are common, particularly with IM injection and castor oil-based preparations. These typically resolve within 24 to 48 hours. A warm compress, paracetamol or ibuprofen as needed, and consistent site rotation all help.
• Bruising may follow if a small vessel is caught during injection. Apply firm pressure for two to three minutes. Significant or expanding bruising warrants medical review.

Pulmonary Oil Microembolism (POME)

POME is a rare but serious event in which oil enters the venous circulation, typically through inadvertent puncture of a small blood vessel during injection. Symptoms — coughing, breathlessness, chest tightness, dizziness, or faintness — occur within minutes of the injection. The risk is greatest with high-volume IM injections; Nebido (4 ml) carries the highest documented risk, which is why it must be administered clinically with a 30-minute post-injection observation period. If any of these symptoms develop after any injection, sit upright and seek emergency medical attention immediately.

Polycythaemia — The Most Important Safety Consideration

Testosterone stimulates red blood cell production. Injectable testosterone, particularly via the IM route, produces higher and more pronounced post-injection peaks than gel, resulting in a stronger erythropoietic stimulus and a greater tendency for haematocrit to rise. This is the most clinically significant haematological risk of injectable TRT.

• If haematocrit exceeds 54%, the risk of venous and arterial thrombotic events increases. Symptoms of elevated haematocrit include persistent headache, dizziness, visual changes, and a ruddy complexion.
• Per BSSM 2023 guidelines: stop testosterone if haematocrit exceeds 54%; do not restart until it falls below 50%; investigate for secondary causes.
• Management options: dose reduction, switch to a lower-peak formulation (such as gel), or therapeutic phlebotomy.
• Risk factors for polycythaemia on TRT: smoking, obstructive sleep apnoea, obesity, older age, and higher testosterone peaks from infrequent IM dosing.

Other Systemic Side Effects

• Acne and oily skin — more pronounced at higher doses or when significant post-injection peaks occur.
• Fluid retention and weight gain — usually mild; monitor blood pressure.
• Worsening obstructive sleep apnoea — inform your prescribing doctor of any new or worsening snoring, choking episodes during sleep, or significant daytime somnolence.
• Gynaecomastia — breast tissue development due to aromatisation of testosterone to oestradiol, more pronounced at higher levels.
• Mood changes — irritability and mood fluctuation are most prominent when pronounced peaks and troughs occur with infrequent dosing. More frequent, lower-dose injections typically reduce this.
• Elevated PSA — expected at physiological testosterone levels and monitored routinely. There is no current evidence that testosterone causes de-novo prostate cancer. The TRAVERSE trial (Lincoff et al., NEJM, 2023) found no significant increase in prostate cancer incidence in 5,204 hypogonadal men treated with testosterone gel versus placebo over 33 months.

When to Seek Emergency Care

• Sudden leg pain, swelling, or redness — possible deep vein thrombosis. Call 999.
• Sudden breathlessness, chest pain, or coughing blood — possible pulmonary embolism or POME. Call 999.
• Persistent erection lasting more than four hours (priapism) — attend A&E immediately.
• Symptoms of POME within minutes of injection (coughing, breathlessness, dizziness) — call 999.

Contraindications

Injectable testosterone must not be used in men with known or suspected prostate cancer, breast cancer, or documented hypersensitivity to testosterone or the oil carrier. Sustanon is specifically contraindicated in men with a peanut or soya allergy. Use with caution in men with obstructive sleep apnoea, thrombophilia, epilepsy, or pre-existing polycythaemia. All contraindications are assessed at the initial clinical consultation before any prescription is issued.

References and Clinical Guidelines