In clinical studies the overall incidence of
side effects was similar to placebo.
Side effects reported included diarrhea, muscle cramps, dizziness, insomnia, and nasal congestion. Losartan also may cause a persistent cough, increase serum potassium, impotence, and angioedema. Losartan may reduce kidney function in some patients and should not be used by patients who have bilateral renal artery stenosis (narrowing of both arteries going to the kidneys).