Drowsiness, dizziness, lightheadedness, stomach upset, diarrhea, nausea, vomiting, or headache may occur. To minimize lightheadedness, get up slowly when rising from a seated or lying position. 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: increased thirst, change in the amount of urine, mental/mood changes, unusual fatigue/weakness, muscle spasms, menstrual period changes, breast pain, breast enlargement (gynecomastia) in men, sexual function problems.This medication may lead to high levels of potassium, especially in patients with kidney problems. If not treated, very high potassium levels can be fatal. Tell your doctor immediately if you notice any of the following unlikely but serious side effects: slow/irregular heartbeat, muscle weakness.Tell your doctor immediately if any of these rare but very serious side effects occur: signs of infection (e.g., fever, persistent sore throat), severe stomach/abdominal pain, persistent nausea/vomiting, vomit that looks like coffee grounds, dark urine, yellowing of the eyes/skin, easy bruising/bleeding.A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction 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.