What it is

This is a clear gel that contains testosterone, the same hormone your body makes. You rub it on your skin, and the testosterone passes through the skin into your blood.¹ Your doctor sets your daily dose from your blood tests.

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How to use it

• Once a day, in the morning, at about the same time. Your skin keeps releasing testosterone into your blood for the whole day, so once a day is enough.²
• Use the whole sachet. Squeeze out all the gel and apply it straight away.¹ Use the number of sachets written on your label.
• Spread it thinly. There is no need to rub it in.¹
• Let it dry for 3–5 minutes, then dress and wash your hands with soap.¹
• Showering. Wait at least 6 hours after applying before you shower or bathe, because that is how long the gel needs to be absorbed. On an occasional busy day, showering after the first hour is fine, because an occasional early shower hardly changes the effect.¹ Never shower within the first hour. For example, if you apply at 7 a.m., shower after 1 p.m.; on an occasional busy day, after 8 a.m.

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Where to apply it, and why

• Both shoulders, both upper arms, or your belly, on clean, dry, unbroken skin.¹ Keep to areas that a short-sleeved T-shirt covers, so you can cover the gel with clothing.²
• Why only these areas. The amount of testosterone each dose gives was measured on these areas, and other areas may give a different level.²
• Never on the penis or scrotum. The gel contains alcohol and will sting.¹ Do not apply it to your chest, armpits, knees or back.²
• Red or irritated skin? Use another of the areas above. Skin irritation is the most common side effect, in about 1 in 10 men. If it is severe, stop and tell us.¹

Where to apply the gel: shoulders, upper arms and belly, under a short-sleeved T-shirt.^1,2

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Protect your partner and children

The gel can pass to other people through skin contact. It can cause unwanted hair growth or a deeper voice in women and children, and it may affect an unborn baby.¹

Waiting alone is not enough. In a study, women had 15 minutes a day of close skin contact with their partner’s uncovered application area, 2 to 12 hours after he applied the gel. All of them had more than double their usual testosterone. When a shirt covered the area, no gel passed across.²

• Cover the area with clothing once the gel is dry, or wash it with soap and water before close skin contact or holding a child.¹
• Pregnant women must not touch the area. Anyone who does touch it should wash their skin with soap straight away.¹

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The gel can catch fire until it is dry

It contains alcohol. Keep away from flames and do not smoke until it has dried.²

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If you miss a dose

If you remember the same day, apply it straight away. If you only remember the next day, skip the missed dose and apply your next dose at the usual time. Never apply a double dose to make up for a missed one.³

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If you stop

Your testosterone returns to your own level within 3 to 4 days of stopping.¹ Because your own production is turned down during treatment, your symptoms are likely to come back. Please talk to us before you stop, so we can plan your follow-up.

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On blood-test days

• Have your blood taken between 7 and 10 a.m., before breakfast, and before you apply your gel. Then apply it after the test.¹ This way every result is taken at the same point of the day and can be compared fairly with the last.
• Stop biotin for at least 3 days before every blood test, because it can interfere with some hormone tests.⁴
• Avoid hard exercise for 2 days before the test, because it can lower your result.
• Drink plenty of water the day before and on the morning of the test.

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Please stop

• Any other testosterone product. Using two products together can push your level too high, and we cannot adjust your dose safely without knowing exactly what you use.
• Anabolic (muscle-building) steroids. Do not use them while on treatment. If you use them, or have recently stopped, please tell us: they switch off your own testosterone, and we do not treat this situation ourselves. We refer you to a hormone specialist (endocrinologist) at a hospital.⁵

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Tell us if you take

None of these means you cannot use the gel. Some medicines and testosterone affect each other, so knowing what you take helps us look after you more closely.

• A blood thinner taken by mouth. Testosterone makes warfarin work more strongly, so the doctor who prescribes it may check your blood clotting more often when you start or stop the gel.² The gel, not the injection, is the right form for anyone on an anticoagulant blood thinner such as warfarin, apixaban, dabigatran, edoxaban or rivaroxaban.
• Insulin or other diabetes medicines. Testosterone can make your body more sensitive to insulin, so your blood sugar may fall and your diabetes medicine may need adjusting.²
• Steroid tablets or injections, or ACTH. Together with testosterone they can cause more fluid retention (swelling).²
• Finasteride or dutasteride (for the prostate or hair loss). They lower the PSA result, so a large trial used half the usual PSA limits for men taking them, and we do the same.⁶
• Thyroid hormone, or upcoming thyroid tests. Testosterone can lower one thyroid result (total T4) while your thyroid itself is fine, so we read the free thyroid result.² Physicians who focus on optimal hormone levels sometimes find the thyroid dose needs a small change.
• Growth hormone. Physicians who focus on optimal hormone levels sometimes find the testosterone dose needs a small change.
• DHEA from anywhere. It adds a little to your testosterone, so we need to know.
• An erection medicine. You can use it together with testosterone.⁵
• Barbiturates (medicines for epilepsy or sleep). They can make your body clear testosterone faster, so your level may be lower than expected.⁷
• Epilepsy or migraine. The product information says these may flare up, so your doctor takes extra care.¹
• Heavy snoring or feeling very sleepy in the day. These can be signs of sleep apnoea (pauses in breathing during sleep), which testosterone may make worse, so we note it and watch your blood count.¹
• Sport that tests for banned substances. Testosterone can give a positive test.¹
• Heavy alcohol or drug use, or anything that makes the gel precautions hard to follow every day. The gel can pass to other people, so in this case we will not prescribe it.¹
• Any new medicine you start while using the gel, so we can check that the two work well together.

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Contact us if you notice

These can be signs that your dose is a little higher than you need. We tell you about them because the earlier we know, the earlier we can adjust your dose, and this is part of good care. They usually have other causes too, and we will check your blood test to be sure.¹

• Spots, oily skin or oily hair.
• Irritability or restlessness, weight gain, or erections that are too frequent or last too long.¹
• Breast tenderness or swelling.
• Swollen ankles.¹
• Passing urine becoming harder.
• Your partner or a child at home develops spots, unusual hair growth or a deeper voice. Stop the gel and tell us.²

Go to a hospital the same day if you have swelling, pain, warmth or redness in one leg, sudden breathlessness, chest pain, signs of a stroke (a drooping face, a weak arm or leg, or slurred speech), severe swelling with breathlessness or being unable to lie flat, or you cannot pass urine. Stop the gel and tell us as soon as you can.^1,2,8

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How to store it

• Store below 30°C. You do not need to keep it in the fridge.
• Keep the sachets in their box and use them before the expiry date on the box.¹
• Keep the gel away from flames until it is dry.
• Keep it out of the sight and reach of children.

Medically reviewed by Dr. Chontirot, MD · Medical licence no. 36583 · Last reviewed: 31 October 2026

References

1. Package insert (Thailand): testosterone gel 50 mg in 5 g sachet, summary of product characteristics.

2. Prescribing information: testosterone gel 1% for topical use (United States). Revised 10/2025.

3. Package leaflet: testosterone 50 mg transdermal gel in sachet (United Kingdom). Revised October 2024.

4. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744. doi:10.1210/jc.2018-00229

5. Salonia A, Boeri L, Capogrosso P, et al. EAU Guidelines on Sexual and Reproductive Health. European Association of Urology; 2026.

6. Bhasin S, Travison TG, Pencina KM, et al. Prostate Safety Events During Testosterone Replacement Therapy in Men With Hypogonadism: A Randomized Clinical Trial. JAMA Netw Open. 2023;6(12):e2348692. doi:10.1001/jamanetworkopen.2023.48692

7. Package insert (Thailand): testosterone undecanoate 1000 mg/4 mL solution for injection. CCDS version 10, 27 September 2021.

8. Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. American Urological Association; 2018.

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