This medication is used in men who do not make enough of a natural substance called testosterone. Testosterone belongs to a class of drugs known as androgens. Testosterone helps the body to develop and maintain male sexual characteristics (masculinity), such as a deep voice and body hair. It also helps to maintain muscle and prevent bone loss, and is necessary for natural sexual ability/desire.Testosterone may also be used in certain adolescent boys to cause puberty in those with delayed puberty.This product should not be used in women.
Testosterone undecanoate is a long-acting man-made version of testosterone, the natural male sexual hormone. Testosterone is responsible for the normal growth and development of male sex organs and characteristics. It includes growth and development of male organs of penis, testicles, prostate, body hair, vocal cord thickening, and muscle and fat distribution. The FDA approved testosterone undecanoate in March 2014.

Nausea, vomiting, headache, skin color changes, increased/decreased sexual interest, oily skin, hair loss, and acne may occur. Pain or redness at the injection site may also occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: breast swelling/tenderness, mental/mood changes (such as depression, agitation, hostility), unusual snoring or difficulty breathing during sleep, swelling hands/ankles/feet, symptoms of liver problems (such as loss of appetite, persistent nausea/vomiting, severe stomach/abdominal pain, yellowing eyes/skin, dark urine), trouble urinating, increased urination (especially at night), too frequent/prolonged erections, fast/irregular heartbeat.
Get medical help right away if you have any very serious side effects, including: shortness of breath/rapid breathing, chest/jaw/left arm pain, unusual sweating, confusion, sudden dizziness/fainting, pain/swelling/warmth in the groin/calf, sudden/severe headaches, trouble speaking, weakness on one side of the body, sudden vision changes.
Rarely, males may have a painful or prolonged erection lasting 4 or more hours. If this occurs, get medical help right away, or permanent problems could occur.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
Before using testosterone, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients (such as benzyl benzoate, refined castor oil), which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: cancer (especially prostate or breast cancer), prostate problems (such as enlarged prostate), heart problems (such as heart failure, previous heart attack), stroke, kidney problems, liver problems, high cholesterol, difficulty breathing during sleep (sleep apnea), blood clots (such as in the leg, lungs).
Testosterone injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- acne
- breast enlargement or pain
- hoarseness
- deepening of voice
- pain, redness, bruising, bleeding, or hardness at injection site
- tiredness
- difficulty falling asleep or staying asleep
- mood swings
- weight gain
- headache
- joint pain
- back pain
Some side effects can be serious. If you experience any of these symptoms or those listed in the IMPORTANT WARNING section, call your doctor immediately:
- lower leg pain, swelling, warmth, or redness
- nausea or vomiting
- swelling of the hands, feet, ankles, or lower legs
- difficulty breathing, especially during sleep
- erections that happen too often or that last too long
- difficulty urinating, weak urine flow, frequent urination, sudden need to urinate right away, blood in the urine
- yellowing of the skin or eyes
- pain in the upper right part of the stomach
- mood changes including depression, anxiety, or becoming suicidal (thinking about harming or killing oneself or planning or trying to do so)

Testosterone injection may cause a decrease in the number of sperm (male reproductive cells) produced, especially if it is used at high doses. Talk to your doctor about the risks of using this medication if you are a man and would like to have children.
Testosterone may increase the risk of developing prostate cancer. Talk to your doctor about the risks of receiving this medication.
Testosterone injection may cause the bones to mature more quickly than normal in children who receive the medication. This means that the children may stop growing sooner than expected and may have a shorter than expected adult height.
Testosterone injection may cause other side effects. Call your doctor if you have any unusual problems while receiving this medication.
Precautions
If you have diabetes, this product may lower your blood sugar. Check your blood sugar regularly as directed and share the results with your doctor. Tell your doctor right away if you have symptoms of low blood sugar, such as sudden sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness, or tingling hands/feet. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).
Children may be more sensitive to the side effects of this drug. In children, it may affect bone growth. Check your child’s height periodically.
Some men, particularly older adults, are at a higher risk for developing enlarged prostate or prostate cancer while using this medication. Your risk of prostate problems should be checked by your doctor before you start testosterone.
This medication can affect fertility in males. Ask your doctor for more details.
This medication should not be used in women, especially during pregnancy or breast-feeding. It may harm an unborn or breast-feeding baby. Consult your doctor for more details.