Itching, irritation, or discomfort at the application site may occur during the first few days as your body adjusts to the patch. Other side effects may include acne, headache, hair loss, anxiety, or a change in sexual desire. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.Remember that your doctor has prescribed this medication because he or she 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 immediately if any of these unlikely but serious side effects occur: breast pain/enlargement, swelling of the feet/ankles (edema), weight gain, very slow/shallow/difficult breathing (possibly while sleeping), unusual weakness.Tell your doctor immediately if any of these rare but very serious side effects occur: trouble urinating, mental/mood changes (e.g., depression, agitation, hostility), change in size/shape of the testicles, testicle pain/tenderness, stomach/abdominal pain, dark urine, yellowing of eyes/skin, change in the amount of urine, calf tenderness/swelling/pain.In the very unlikely event you have a painful or prolonged erection lasting 4 or more hours, stop using this drug and seek immediate medical attention, or permanent problems could occur.Rarely, burn-like reactions under the patch may occur. This is most likely to happen if the patch is placed on bony areas of the body (see How to Use section for proper application sites). Permanent scarring may occur, so tell your doctor immediately if this type of reaction occurs while you are using this patch.If you have diabetes, especially if you are using insulin, testosterone may decrease your blood sugar. Be prepared to treat low blood sugar while you are using this medication. Symptoms of low blood sugar include shakiness, nervousness, rapid pulse, and sweating. If you are experiencing these symptoms, consult your doctor. Your doctor may need to adjust your diabetes medications.Female partners of men using this medication have a slight chance of developing changes in hair location, an increase in acne, and other signs of the effects of testosterone. If your female partner develops any of these symptoms, tell both of your doctors.A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction may include: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.In the US -Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.