The most common side effect associated with diuretics is potassium loss. With the exception of potassium-sparing versions, all diuretics may cause a loss of potassium. Rarely, potassium-sparing diuretics can cause a build-up of potassium in the body. Symptoms of potassium loss include:

• Tiredness
• Weakness
• Numbness
• Tingling
• Muscle cramps
• Constipation
• Vomiting
• Fast heartbeat (tachyarrhythmia)

Patients should contact their physicians if they have any of the following side effects from diuretics, most of which are related to diuresis (urinating too much) and dehydration:

Less common side effects of diuretics may include:

• Allergic reaction
• Fainting (syncope)
• Increased sensitivity to sunlight, causing severe sunburn or rash
• Blurred vision
• Confusion or nervousness
• Diarrhea, stomach cramps or pain
• Loss of appetite
• Difficult or painful urination
• Muscle twitches or spasms
• Joint pain
• Fever or chills
• Erectile dysfunction (impotence) or decreased desire for sex
• Headache or ringing in ears
• Unusual bleeding or bruising
• Jaundice (yellow tint to the skin or eyes)
• Mood change
• Weight changes

Rarely, potassium-sparing diuretics may produce breast enlargement in males and females, causes breast tenderness, deepening of the voice, increased hair growth, irregular menstrual periods and unusual sweating.

Patients on diuretics should inform their physicians if they become sick, especially with severe or continuing vomiting or diarrhea. These conditions can cause the body to lose too much water and potassium.