By far, the most common side effect associated with ACE inhibitors is a dry, persistent cough, which occurs in up to 20 percent of patients. It tends to affect women more often than men and usually begins within one to two weeks of starting the medication, although it can be delayed for up to six months.  This side effect is usually not serious, but it often leads the physician to change the patient to a different class of medications, such as the closely related angiotensin II receptor blockers (ARBs). Rarely, stridor (swelling within the airway) may occur, requiring prompt hospital treatment.

A potentially serious side effect is hyperkalemia – an abnormally high level of potassium in the blood. Therefore, patients usually have regular blood tests to check potassium levels and avoid any serious consequences. This test is essential because most people will not be aware of a rise in potassium.

Patients may also experience acute renal (kidney) failure or a decline in kidney function. This typically occurs in patients who have existing kidney disease.

Also, people should seek medical attention immediately if they experience any side effects that could indicate an allergic or other severe reaction to ACE inhibitors. These side effects include:

Other side effects of ACE inhibitors include: 

• Allergic reaction (sneezing, respiratory congestion, itching or skin rashes)
• Tachycardia (abnormally fast heartbeat)
• Edema (swelling) in the face, mouth, hands or feet
• Headache
• Drowsiness, weakness or fatigue
• Loss of taste (especially with captopril)
• Diarrhea
• Nausea or upset stomach
• Vomiting
• Abdominal cramps, pain or distention
• Joint pain
• Chest pain
• Jaundice (rare, but serious)

When first taking ACE inhibitors, or after any increase in dosage, there is a possibility of a “first dose effect.” During the first dose effect, the patient’s blood pressure drops rapidly, which causes dizziness, nausea and possibly fainting. To avoid experiencing the first dose effect, it may be recommended that the first dose of this medication be taken at bedtime, or the physician may recommend that the patient forgo other medications (e.g., diuretics) for a few days after starting therapy.

In addition, ACE inhibitors rarely cause a decrease in white blood cells in some patients, making them more prone to infection. Patients should report any signs of infection to their physician immediately, which include fever, sore throat, nausea or vomiting.