Testosterone gel vs injections: how the UK options compare

Published 22 October 2026

Testosterone gels and injections contain the same hormone. What differs is how it reaches your bloodstream, how often you deal with treatment, how steady your level stays, and whether anyone else in your home could be exposed. This page compares the UK options side by side using the official product information and NHS guidance, and it assumes low testosterone has already been confirmed: if it has not, the first step is a proper assessment, not a choice of product.

Is testosterone gel or injection better?

Neither is better for every man. Gels and injections both deliver testosterone itself, and both can bring a genuinely low level back into the normal range. Gels give relatively steady levels and can be stopped within days, but need a daily routine and care around other people. Injections remove the routine and the skin-transfer risk, but levels rise and fall between doses, and an injection cannot be taken back once given.

Two things do not change whichever route you choose. Treatment is only appropriate once a deficiency has been confirmed, as our testosterone replacement therapy page explains. And every form of testosterone can suppress sperm production, so no route protects fertility.

Practice varies. One NHS Scotland formulary states that a depot injection is usually preferred, with gel chosen if a man finds injections painful or would rather treat himself. In our clinic a gel is usually the starting point, because the dose can be adjusted and treatment stopped quickly.

What testosterone treatments are available in the UK?

In the UK, testosterone replacement is given either through the skin as a gel or into a muscle as an injection:

• Gels: Testogel (in a pump or single-use sachets), Tostran and Testavan, each applied once a day.
• Short-acting injections: such as Sustanon, a blend of four testosterone esters (chemically modified forms of testosterone) dissolved in oil.
• Long-acting injection: testosterone undecanoate, sold under brand names including Nebido and Roxadin.

Oral testosterone undecanoate capsules are still listed in the NHS Dictionary of Medicines and Devices, but it records that no products are currently available, so this comparison concentrates on gels and injections.

How do gels and injections compare side by side?

Gels are daily and steadier; injections are less frequent, but levels rise and fall between doses. This table draws on the UK product information and NHS guidance; the sections below explain each row.

Scroll the table sideways to see every column

Why do injections cause peaks and troughs?

Because a whole dose is placed in the muscle at once and released over the following weeks, rather than topped up every day. In an injection, testosterone is attached to an ester and dissolved in oil; as it reaches the bloodstream the ester is split off, leaving ordinary testosterone.

Sustanon’s product information describes levels peaking about 24 to 48 hours after an injection and drifting back to the lower limit of the normal male range in roughly 21 days. An NHS hospital leaflet lists end-of-dose fluctuation in symptoms as a drawback, which some men notice before the next injection is due.

Testosterone undecanoate is released more slowly. NHS formulary guidance notes that it offers less fluctuation between doses than other intramuscular preparations, and less frequent injections, although it is more expensive than other intramuscular preparations.

Gels are absorbed through the skin after each daily application, and Testogel’s product information states that steady levels are usually reached by the second day. They are not perfectly flat: Testavan’s product information describes a peak two to four hours after application, with levels back to the pre-application value about 12 hours later. But the pattern repeats daily rather than over weeks, which is why the King’s College Hospital patient leaflet describes gels as giving stable blood levels.

How often are testosterone injections given?

Short-acting injections are given every few weeks, and the long-acting injection every 10 to 14 weeks.

• Sustanon: the product information states that one injection every three weeks is usually adequate, adjusted to the individual, and an NHS hospital leaflet describes intervals of two to four weeks. Some men are given injections more often; your consultant will advise.
• Testosterone undecanoate (Nebido): every 10 to 14 weeks once established; your consultant may shorten the first interval so that steady levels are reached sooner.

For testosterone undecanoate, the product information allows the interval to be adjusted, based on a blood test taken at the end of an interval, just before the next injection is due. Your consultant uses those results, with how you feel, to set the interval.

Testogel vs Nebido, and Sustanon vs Nebido

The main difference is how long each lasts: Testogel works day to day, Sustanon about three weeks and Nebido 10 to 14 weeks.

Testogel vs Nebido

This is the choice between the most hands-on option and the most hands-off one. Testogel is applied daily, and stopping is quick, with levels back to baseline within three to four days of the last application. The trade-off is the routine and protecting others from skin contact. Nebido is given four or five times a year with no transfer risk, but once injected it keeps acting for months: each injection is designed to last 10 to 14 weeks, and the product information describes a release half-life of about 90 days. That is why we normally reserve long-acting injections for men who have already tolerated testosterone on a shorter-acting preparation.

Sustanon vs Nebido

Both are oily injections into muscle. Sustanon’s shorter action means more pronounced peaks and end-of-dose dips, while Nebido fluctuates less but takes far longer to wear off if it needs to be stopped. Sustanon contains arachis (peanut) oil and must not be used by men allergic to peanuts or soya. The product information for both carries the same warning: rarely, oil can reach the lungs (pulmonary oil microembolism), causing cough, breathlessness, chest pain, dizziness or fainting during or just after the injection. These reactions are described as reversible.

Can testosterone gel transfer to a partner or child?

Yes. Testosterone gel can pass to another person through skin contact, and Testogel’s product information states that, without precautions, this can happen at any time after application. In January 2023 the MHRA, the UK medicines regulator, published a Drug Safety Update after reports of premature puberty and genital enlargement in children who had repeated close contact with an adult using topical testosterone. In women, exposure can cause facial or body hair growth, a deeper voice and menstrual changes. Pregnant women must avoid contact with application sites, because testosterone can have virilising effects on an unborn baby.

The MHRA advises that you:

• wash your hands with soap and water after applying the gel;
• cover the area with clean clothing, such as a T-shirt, once it has dried;
• wash the application site before close physical contact with another adult or a child, once the recommended time for your product has passed.

If you think a child or partner may have been exposed, seek medical advice and mention the gel.

How the UK testosterone gels differ

These details come from each product’s current UK information; always follow the leaflet supplied with your own prescription, as guidance is updated.

Scroll the table sideways to see every column

Washing too soon can reduce how much testosterone is absorbed, as Testavan’s product information explains. Gels are kept away from the genitals; Testogel’s high alcohol content may irritate the skin there.

Does every type of testosterone affect fertility?

Yes. Every testosterone gel and injection can suppress sperm production, and no route avoids this; the UK product information for these preparations warns about it. The mechanism is the same whatever the route. When testosterone comes from outside the body, the pituitary gland at the base of the brain turns down its two signalling hormones: luteinising hormone (LH), which drives the testicles’ own testosterone production, and follicle-stimulating hormone (FSH), which supports sperm production.

The product information describes this suppression as reversible, but recovery after stopping can take time, and with a long-acting injection the effect continues until the last dose has worn off. If you hope to father children now or in the future, speak to a specialist before starting any form of testosterone; other ways of managing a hormone imbalance are discussed on our male fertility treatment page. If you are already using any form of testosterone and are thinking about children, raise it before changing or stopping treatment so that a plan can be made.

What monitoring does each option need?

The safety checks are broadly the same for gels and injections; what differs is when the testosterone blood test is taken. Product information for both recommends regular monitoring of testosterone, haemoglobin and haematocrit, liver function and blood fats during long-term treatment.

• Haematocrit is the proportion of the blood made up of red cells. Testosterone can raise it, thickening the blood, and an NHS hospital leaflet notes this may be associated with a higher risk of heart attack, stroke and blood clots. Nebido’s product information adds that SGLT-2 inhibitors, a group of diabetes medicines, can also raise haematocrit, and recommends monitoring in men taking both.
• Prostate: androgens can enlarge the prostate and may speed up a cancer already present but not yet detected. Gel and Nebido product information recommends a prostate examination and PSA test at least yearly, and twice yearly in older and higher-risk men; Sustanon’s suggests these checks, with haematocrit, before starting, every three months for the first year and yearly after that. See prostate conditions and PSA levels by age.
• Testosterone timing: for the long-acting injection, at the end of an interval; for gels, as set by each brand (see the table above). Tell whoever takes your blood which preparation you use and when you last used it.

Our own review schedule is described on our TRT page.

Call 999 or go to A&E if you develop chest pain or sudden breathlessness, signs of a stroke such as face drooping, arm weakness or slurred speech, or an erection lasting more than 3 to 4 hours (priapism, a rare listed side effect). For a painful, swollen calf without chest pain or breathlessness, ask for an urgent GP appointment or contact NHS 111. If you suddenly cannot pass urine despite a full, painful bladder, get same-day help from NHS 111, your GP or A&E (see problems passing urine). Report too frequent or persistent erections to your consultant, as the dose may need adjusting. Tell staff straight away if you feel breathless, cough or feel faint during or just after an injection. For visible blood in your urine, breast swelling or a persistent skin reaction, contact us or your GP, or call NHS 111.

Which option might suit your situation?

Your consultant will talk through what fits your health, household and routine. Factors that often matter:

• Young children at home, or a pregnant partner: an injection avoids the transfer risk.
• Disliking needles, or wanting to manage treatment yourself: a gel is self-applied.
• Wanting to be able to stop quickly: gel levels start falling within about a day; a long-acting injection lasts months.
• Skin irritation from gel: with Tostran, rotating daily between the abdomen and inner thighs, as its product information recommends, can help; Testogel and Testavan should stay on the sites their leaflets specify. Otherwise another preparation may suit you better.
• Wanting children: no preparation protects fertility, so seek specialist advice first.

Talking through TRT options with a specialist

To choose or review a preparation, or to find out whether TRT is right for you, you can see one of our specialists, who all practise at Guy’s & St Thomas’, named by Newsweek in 2025 as the number one urology service in Europe. We see patients at HCA at The Shard, HCA at Canary Wharf and HCA at Guy’s Hospital; our guide to your first urology appointment explains what to expect.

Initial consultations cost £300 to £350 depending on the specialist and appointment type, with tests quoted separately (see fees and insurance). Self-funding patients need no GP referral; insured patients usually need one, plus insurer pre-authorisation. Call +44 7889 318584 (Monday to Friday, 8am to 4pm), email contact@theandrologycentre.co.uk or use our contact page.

Frequently asked questions

References and further reading