Testosterone belongs to the class of medications called androgens (male hormones). This medication is used to replace testosterone in males who have conditions caused by low testosterone levels. It is also used to treat erectile dysfunction (erectile difficulties or the inability to attain or maintain an erection) and other male sexual problems when they are caused by low testosterone levels.

This medication works by replacing the testosterone that would normally be produced by the body. Testosterone should only be used if testosterone deficiency has been confirmed by symptoms and blood tests.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The dose of testosterone undecanoate is adjusted according to the response of the person taking the medication. The starting dose of testosterone undecanoate is usually 120 mg to 160 mg, taken in two divided doses. After the first 2 to 3 weeks of treatment, the dose of testosterone undecanoate usually ranges from 40 mg to 120 mg daily. Take capsules with a meal and swallow them whole without chewing them.

If your dose is greater than one capsule, take half of your daily dose in the morning and half in the evening. If you are taking an odd number of capsules, take the larger number in the morning.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not take this medication if you:

• are allergic to testosterone or any ingredients of the medication
• are female (especially if you are pregnant or breast-feeding)
• have, or are suspected to have, prostate or breast cancer

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• abdominal pain
• acne
• aggressive behaviour
• changes in sexual desire or drive
• confusion
• dizziness
• enlarged prostate
• hair loss, thinning hair, or baldness
• headache
• loss of appetite
• mood changes
• skin rash or itching
• sleep disturbances caused by breathing problems (sleep apnea)
• sore throat and/or fever
• unpleasant breath odour
• unusual tiredness
• weight gain

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• breast soreness or enlargement
• fast or irregular heart rate
• flushing or redness of skin or any changes in skin colour
• high blood pressure
• problems with urination (change in frequency or colour, dribbling, pain or straining when urinating, weak urine stream, small urine amounts)
• purple or red-coloured spots on the body or inside the mouth or nose
• shortness of breath
• signs of a blood clot in the arm or leg (tenderness, pain, swelling, warmth, or redness in the arm or leg) or lungs (difficulty breathing, sharp chest pain that is worst when breathing in, coughing, coughing up blood, sweating, or passing out)
• signs of clotting problems (e.g., unusual nosebleeds, bruising, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
• signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
• swelling of ankles and legs (for people with heart, liver, or kidney problems)
• symptoms of liver problems, such as:
• abdominal pain
• dark urine
• loss of appetite
• nausea or vomiting
• pale stools
• yellow eyes or skin
• unusual fatigue or bleeding

Stop taking the medication and seek immediate medical attention if any of the following occur:

• prolonged (more than 4 hours) or painful erections, or erections that happen too often
• signs of bleeding in the stomach (e.g., bloody, black, or tarry stools, spitting up of blood, vomiting blood or material that looks like coffee grounds)
• signs of a heart attack (e.g., chest pain or pressure, pain extending through shoulder and arm, nausea and vomiting, sweating)
• signs of stroke (e.g., sudden or severe headache; sudden loss of coordination; vision changes; sudden slurring of speech; or unexplained weakness, numbness, or pain in arm or leg)
• symptoms of a serious allergic reaction, such as:
• difficulty breathing
• hives
• rash
• swollen face or throat

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Blood tests: Your doctor may recommend that you have regular blood tests while using this medication to check whether the medication is working and whether you are having certain side effects. Also, the use of testosterone may interfere with a number of laboratory tests. Tell all health professionals administering these tests that you are using this medication.

Breast cancer: Long-term use of testosterone may increase the risk of developing breast cancer. Talk to your doctor if you have concerns.

Diabetes: Testosterone undecanoate may cause a loss of blood glucose control, and glucose tolerance may change. People with diabetes may find it necessary to monitor their blood sugar more frequently while using this medication. If you have diabetes or are at risk for developing diabetes, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Heart disease: Testosterone can cause increased blood pressure and may cause fluid to build up in the body. Both conditions can increase the risk of certain types of heart disease.

In addition, androgens have been linked to increased risk of heart disease, including congestive heart failure, heart attack and stroke. If you have heart disease or risk factors for developing heart disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Prostate problems: Medications such as testosterone may increase the speed at which prostate cancer or benign prostatic hypertrophy (BPH, or enlarged prostate) progresses. If you have a history of prostate cancer or BPH, or you are at risk of developing prostate cancer, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Sleep disorders: Treatment with testosterone may cause sleep apnea (interruption of breathing during sleep) and high blood pressure for some people, especially those with risk factors such as being overweight or having a chronic lung disease.

Sperm counts: This medication may reduce sperm counts if high doses are used, or if it is used for a prolonged period.

Pregnancy: This medication is not recommended for pregnant women.

Breast-feeding: This medication is not recommended for breast-feeding women.

Children: The safety and effectiveness of using this medication have not been established for children. This medication is not recommended for children under 18 years of age.

Seniors: Seniors may have an increased risk for prostate enlargement and should be evaluated for prostate cancer before starting testosterone replacement therapy. There is limited data to support the safety and effectiveness of prolonged use of this medication in people over the age of 65 years.

There may be an interaction between testosterone undecanoate and any of the following:

• abiraterone
• busulfan
• corticosteroids (e.g., dexamethasone, hydrocortisone, prednisone)
• cyclosporine
• darbepoetin alfa
• dehydroepiandrosterone
• diabetes medications (e.g., acarbose, canagliflozin, glyburide, insulin, linagliptin, lixisenatide, metformin, rosiglitazone)
• disopyramide
• esketamine
• hydroxychloroquine
• octreotide
• pasireotide
• protein kinase inhibitors (e.g., dasatinib, ibrutinib, lenvatinib, sunitinib)quinine
• sirolimus
• somatostatin acetate
• sulfonamide antibiotics ("sulfas"; e.g., sulfisoxazole, sulfamethoxazole)
• tacrolimus
• tramadol
• warfarin

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should