These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Furosemide (Lasix) side effects include frequent urination, headaches, and dizziness. It can also cause drops in blood pressure when changing positions (like from sitting or laying down to standing) and make you more sensitive to the sun. Furosemide works by blocking the absorption of sodium, chloride, and water from the filtered fluid in the kidney tubules, causing a profound increase in the output of urine (diuresis). The onset of action after oral administration is within one hour, and the diuresis lasts about 6-8 hours. Possible side effects of diuretics include: Most people can take diuretics without getting serious problems from them. But your healthcare provider will want to make sure your kidneys are working right and your potassium level is normal when you’re taking water pills. Hydrochlorothiazide (Microzide), furosemide (Lasix), and spironolactone (Aldactone) are a few popular examples. Diuretics can cause side effects, such as increased urination, dizziness, and headaches. Diuretics, sometimes called water pills, help remove extra fluid from the body. They're often used to lower blood pressure. Know the possible side effects. Learn about the side effects of Lasix (furosemide), from common to rare, for consumers and healthcare professionals. Lasix is a loop diuretic (water pill) that prevents your body from absorbing too much salt, causing it to be passed in your urine. Lasix treats fluid retention (edema) in people with congestive heart failure, liver disease, or kidney disorders such as nephrotic syndrome. LASIX® (furosemide) is a potent diuretic which, if given in excessive amounts, can lead to a profound diuresis with water and electrolyte depletion. Therefore, careful medical supervision is required and dose and dose schedule must be adjusted to the individual patient's needs. Find patient medical information for Furosemide (Lasix) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings.