Diuretics, also known as water pills, are medications that stimulate the kidneys to produce more urine, flushing excess fluids from the body. They are frequently prescribed to treat a number of conditions, including high blood pressure, heart failure and kidney disease.
Reducing salt and water levels in the body lowers blood pressure throughout the body, decreasing stress on the heart, kidneys and other organs. Large-scale studies have found that diuretics reduce the risk of heart attack and stroke.
People with diabetes who take diuretics should carefully monitor their glucose (blood sugar) levels because these medications may increase the risk of hyperglycemia (high blood glucose). In addition, use of diuretics by nondiabetics may increase their risk of developing diabetes. A physician will decide if diuretics should be incorporated into an individual’s treatment plan.
Diuretics are non-habit-forming medications that stimulate the kidneys to produce more urine, flushing excess fluids and minerals (e.g., sodium) from the body. They are a class of antihypertensives, used to treat high blood pressure. They are also used to treat other conditions, such as heart failure and kidney disease.
There are four general types of diuretics:
- Thiazide or thiazide-like
Research has suggested that use of diuretics may increase the risk of developing diabetes. Individuals with diabetes who take diuretics must carefully monitor their glucose (blood sugar) levels because of increased risk of hyperglycemia (high blood glucose).
The benefits of using diuretics may outweigh the potential risks for most people. For instance, high blood pressure is common among people with diabetes and is a leading contributor to heart disease and stroke among diabetes patients. A physician can determine if an individual will benefit most from a diuretic, other antihypertensive or other medication.
Types and differences of diuretics
The most common diuretic medications fall into four major categories:
- Loop diuretics decrease the ability of the kidneys to absorb sodium, causing more sodium to be eliminated through urine. Loop diuretics produce the greatest increase in urine flow. They may be administered through an intravenous (I.V.) line in the hospital to reduce swelling (edema) in patients with a variety of conditions (e.g., heart failure). They are most commonly used as oral medications. Types include:
ethacrynic acid (Edecrin)
ethacrynate sodium (Edecrin Sodium)
- Thiazide (or thiazide-like) diuretics increase the excretion of both sodium and chloride into the urine. They are commonly prescribed for heart patients, either alone or in conjunction with a potassium-sparing version. They are also commonly used to treat high blood pressure. Types include:
chlorothiazide (Diuril, Diurigen)
chlorthalidone (Clorepres, Hygroton, Tenoretic, Thalitone)
hydrochlorothiazide* (Esidrix, Ezide, HydroDIURIL, Hydro-Par, Microzide, Oretic)
methyclothiazide (Aquatensen, Enduron)
metolazone (Mykrox, Zaroxolyn)
trichlormethiazide (Metahydrin, Naqua)
(* also available in the combination drug Tekturna HCT, which includes a renin inhibitor called aliskiren)
- Potassium-sparing diuretics are used to protect the body from excess potassium loss, which can occur with loop and thiazide diuretics. Far less potent, potassium-sparing diuretics are commonly used with the other forms of diuretics. They are also frequently used in patients with liver disease and ascites (fluid buildup in the abdomen due to liver damage). In addition, they can be used to treat high blood pressure and low potassium levels. Types include:
|amiloride hydrochloride (Midamor)|
- Osmotic diuretics are the least-used form of diuretics. They draw fluid from the cells of the brain and eyes, as well as increase the elimination of toxins introduced into the body (from legal or illegal drugs) through urine. The mechanic process involves the increase of osmotic pressure (ion concentration) in blood and blood vessels, inhibiting the reabsorption of water and dissolved substances, and causing an increase in urine flow. Types include:
|glycerin (Glyrol, Osmoglyn)|
isosorbide (Dilatrate, Imdur, Ismo, Isordil, Monoket)
Diuretics are also available in many combination drugs. Diuretics are generally taken orally in tablet, capsule or liquid form. They can also be administered through intravenous injection if immediate treatment is necessary.
Conditions treated with diuretics
Many physicians consider diuretics to be a front-line treatment for high blood pressure (hypertension).
A large-scale study conducted by the National Institutes of Health concluded that, in people with diabetes, prediabetes or normal glucose (blood sugar), diuretics were more effective at preventing cardiovascular problems and kidney failure than other blood pressure medications. The study, known as the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), also indicated that diuretics had advantages in treating people with metabolic syndrome, especially black participants. Several other studies have also found diuretics particularly effective for black patients.
The ALLHAT study concluded that treatment for high blood pressure should begin with diuretics. For those who cannot tolerate diuretics, a calcium channel blocker, ACE inhibitor or beta blocker can be used to start. Another finding of the study was that, overall, most individuals need more than one drug to treat high blood pressure, and one of those drugs should be a diuretic.
However, the study has generated great controversy within the medical community. Specifically, patients on diuretics achieved lower blood pressures than patients in the other groups, creating the impression that those other groups were not treated aggressively enough. Furthermore, patients in the diuretic group were more likely to develop diabetes; the long-term consequences of this were not addressed in the study.
In addition, some other recent large-scale studies, including the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT), indicated that newer antihypertensives such as calcium channel blockers and ACE inhibitors may, unlike older antihypertensives including beta blockers and diuretics, help keep nondiabetics from developing diabetes. ACE inhibitors and a related group of antihypertensives called angiotensin II receptor blockers (ARBs) may have particular benefits for people with diabetes. Many factors can affect how an individual responds to a diuretic or other antihypertensive, including genetics. Patients are advised to ask their physician about the best drug or combination of treatments for their particular situation.
In addition to high blood pressure, diuretics are used to treat conditions including:
- Diabetes insipidus (thiazide diuretics only). A pituitary gland disorder marked by excessive thirst (polydipsia) and the excretion of large amounts of urine (polyuria). Thiazide diuretics actually decrease urine volume in patients with diabetes insipidus (water diabetes), which is unrelated to diabetes mellitus (sugar diabetes).
- Heart failure. By flushing excess fluids from the body, diuretics can relieve the edema (swelling from excess fluids) that commonly occurs with heart failure. Specifically, spironolactone and eplerenone have been independently shown to benefit patients with heart failure and poor heart function in patients already taking loop diuretics.
However, a recent study has shown that spironolactone increased the risk of high potassium levels, a condition called hyperkalemia, leading to higher rates of hospitalization and mortality. This risk was more pronounced in patients taking ACE inhibitors, as well as angiotensin II receptor blockers (ARBs) and potassium supplements.
- Renal insufficiency. A condition in which the kidneys are unable to function normally. In some cases, diuretics may worsen this condition.
- Cirrhosis. Destruction and scarring of liver tissues, when complicated by ascites (fluid buildup in the liver caused liver cirrhosis, heart failure or kidney disease).
- Hypercalcemia. Too much calcium in the blood. Causes of hypercalcemia include diseases of the parathyroid glands, cancer and sarcoidosis (disease in which inflammatory lumps form in the lungs and other organs).
- Glaucoma (osmotic diuretics only). An eye disease in which damage to the optic nerve causes loss of sight, usually gradually. People with diabetes face an increased risk of glaucoma and other eye diseases.
- Cerebral edema (osmotic diuretics only). A potentially fatal swelling in the brain that can be caused by hemorrhage, trauma, disease or surgery.
- Drug intoxication (osmotic diuretics only). Osmotic diuretics increase the urinary excretion of toxins introduced into the body through the use of many legal and illegal substances.
- Hyperaldosteronism (potassium-sparing diuretics only). A condition in which the increased production of the hormone aldosterone causes increased blood pressure, excessive potassium loss and muscle weakness.
- Polycystic ovarian syndrome. A disorder marked by irregular menstruation, obesity, increased hair growth, cystic ovaries and infertility. This is a common condition in women who have diabetes.
- Osteoporosis. A bone-thinning disease that is most common in women after menopause. Recent research indicates that women and men with diabetes, especially type 1 diabetes, are at increased risk of osteoporosis and fractures. Calcium-sparing diuretics, such as thiazides, may be prescribed to help treat osteoporosis. However, diuretics that promote the release of calcium into the urine, such as loop diuretics, can worsen this disease.
Conditions of concern with diuretics
Patients are advised to use diuretics with caution if they have been diagnosed with any of the following conditions:
- Diabetes. Careful glucose monitoring is required when people with diabetes take diuretics because these drugs increase the risk of hyperglycemia (high glucose). However, people with diabetes are commonly prescribed diuretics if the benefit (e.g., treatment of high blood pressure or heart failure) outweighs the risk.
- High cholesterol levels (hyperlipidemia) (for thiazide diuretics only). Excess fat (lipids) in the blood.
- Severe liver or kidney disease (e.g., diabetic nephropathy) or a history of kidney stones. The effect of the diuretic may be increased because of the slow removal of the drug from the body by these organs.
In addition, diuretics may make some disorders worse. Patients with the following conditions should discuss the risks with their physicians:
- Gout. An especially painful type of arthritis caused by an excessive amount of uric acid in the blood and deposits of urates in and around joints. The risk of gout is increased in people with type 2 diabetes, kidney disease, obesity, high blood pressure or hyperlipidemia.
- Hearing problems. Some people with diabetes have impaired hearing because of diabetic neuropathy.
- Pancreatitis. Inflammation of the pancreas.
- Menstrual problems or breast enlargement (potassium-sparing diuretics only).
- Osteoporosis (calcium-depleting diuretics only; calcium-sparing diuretics may be used to help treat osteoporosis).
Potential side effects of diuretics
The most common side effects associated with diuretics are excessive urination (polyuria) and loss of potassium. With the exception of potassium-sparing versions, all diuretics may cause a loss of potassium in patients. Rarely, potassium-sparing diuretics can cause a buildup of potassium in the body.
Individuals with diabetes may find that use of diuretics disrupts levels of glucose (blood sugar). These individuals must frequently perform glucose monitoring and may need to consult with their physician for possible changes in their diabetes management plan.
Patients should contact their physician if they have any of the following side effects from diuretics, most of which are related to polyuria and dehydration:
- Dry mouth
- Increased thirst (polydipsia)
- Arrhythmia (abnormal heartbeat)
- Confusion, mental changes or moodiness
- Muscle cramps or pain
- Numbness or tingling in the hands and feet
- Nausea or vomiting
- Unusual fatigue or weakness
- Weak pulse
- Heaviness or weakness of the legs
- Dizziness or lightheadedness, especially after getting up from a sitting or lying position
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 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 in females, cause breast tenderness, deepening of the voice, increased hair growth, irregular menstrual periods and unusual sweating.
Patients on diuretics should inform their physician 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.
Drug or other interactions with diuretics
Patients should consult their physician before taking any additional prescriptions, over-the-counter medications or nutritional supplements. For example, it is known that patients taking antidiabetic agents and insulin are at risk for high glucose (hyperglycemia) when those medications are combined with thiazide diuretics and beta blockers. Other substances that can influence the effects of diuretics include:
- Otherantihypertensives (drugs that slow heart rate or lower blood pressure) such as ACE inhibitors. Although commonly prescribed to diabetes patients, these can strengthen the effects of diuretics and potentially lead to low blood pressure (hypotension).
- Psychiatric medications. Some diuretics can cause a buildup of these medications in the blood, increasing the chance of side effects.
- Licorice. Eating certain types of licorice while taking diuretics may cause excessive loss of potassium.
Alcohol use, exposure to heat and prolonged standing may also intensify the adverse effects of diuretics.
Symptoms of diuretic overdose
Signs and symptoms of overdose can be similar to the medication’s side effects but are usually more severe. The physician should be contacted if patients experience complications, which may include:
- Extreme thirst (polydipsia)
- Severe low blood pressure (hypotension)
- A fast or irregular heartbeat (tachycardia)
- Severe dizziness or fainting (syncope)
- Deafness or ringing in the ears
- Poor skin tension
- Muscle cramps or weakness
- Weak pulse
- Cardiac arrest
- Deep sleep or coma (prolonged unconsciousness)
Lifestyle considerations with diuretics
When first taking a diuretic, patients should avoid driving or operating other heavy machinery until they know how the medication will affect them. Some patients may experience fatigue when first taking this medication, but this usually passes after the patient has been on the medication for some time. Urine flow will increase and some patients may need to wake during the night to urinate. To minimize this, patients with a single daily dose may be advised by their physician to take their medication in the morning after breakfast.
Patients taking more than one dose a day are likely to be advised to take their last dose before 6 p.m. In addition, some diuretics can increase the skin’s sensitivity to sunlight. Patients are advised to use sunscreen and avoid tanning booths. Furthermore, patients being treated for heart failure may need to weigh themselves frequently and report any loss or gain of more than 5 pounds in a week.
Patients should drink enough liquids during exercise or in hot weather to avoid dehydration and follow their physician’s instructions regarding activity levels and diet. Physicians may instruct patients to add foods high in potassium to their diets or prescribe a potassium supplement, but patients should not attempt to change their diet without direction from their physician. Extra potassium is not necessary for every patient on diuretics and too much potassium can be harmful. In addition, patients taking loop diuretics may be advised to take magnesium supplements, in addition to potassium supplements, because the reabsorption of this solute is limited by the medication.
Most patients on diuretics to treat high blood pressure (hypertension) will be taking the medication for the rest of their lives, provided no serious side effects occur. Patients should remember that diuretics can help to control high blood pressure but cannot cure it. Even if all their symptoms cease, patients should continue to take their medication as directed and to keep all scheduled follow-up appointments with their physician.
Pregnancy use issues with diuretics
Use of diuretics during pregnancy is not recommended. The effects of diuretics during pregnancy have not been studied extensively. However, it has been noted that diuretics given after the first trimester to treat high blood pressure may interfere with the normal expansion of fluid seen during pregnancy. The depletion of this fluid volume could, in turn, disrupt neurodevelopment of the fetus and increase the risk of conditions such as schizophrenia in the child. There is also a risk of jaundice, blood problems and potassium depletion in the newborn.
In breastfeeding women, most diuretics will pass into breast milk and can cause dehydration in nursing infants. Potassium-sparing diuretics, however, have not been found to cause problems in nursing babies.
Child use issues with diuretics
The use of diuretics in children is typically seen for the treatment of milder degrees of heart failure. There is no indication that the risk of side effects from diuretics is different in children than in adults. Dosages are lower for children and the dosage interval may be longer.
Children taking potassium-sparing diuretics are more prone to developing calcium deficiencies than are adults. Safety of diuretic use in children has not been scientifically established for all forms of the medication. Parents are encouraged to discuss the potential risks and benefits with a board-certified pediatric cardiologist before their child begins taking diuretics.
Elderly use issues with diuretics
Older adults have a higher frequency and intensity of side effects, such as lightheadedness, dizziness and fainting (syncope). They are also more susceptible to dehydration, hypovolemia (decrease in circulating blood volume), and deficiencies of calcium, potassium, sodium and magnesium. Generally, older patients require lower doses of diuretics and require close observation but are routinely prescribed these medications.
Recent research has supported aggressive treatment of high blood pressure in the elderly. In 2007 the international Hypertension in the Very Elderly Trial was halted early after it found major reductions in stroke and death in people age 80 and older who were treated with a diuretic and an ACE inhibitor.
Questions for your doctor about diuretics
Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about diuretics:
- Are diuretics safe for me to use?
- Am I taking a diuretic for high blood pressure or for another condition?
- How will taking a diuretic help my condition?
- Which type of diuretic is recommended for me? What is the name, dosage and frequency?
- How and when should I take the drug?
- Can diuretics affect my risk of hyperglycemia, kidney disease or other complications?
- Does my diuretic deplete potassium?
- Does my diuretic help my body keep calcium or lose calcium?
- Should there be increased monitoring of my glucose levels, kidney health, bone health or anything else?
- Are there any symptoms that might indicate my diuretic is not working properly?
- What are the possible side effects, and at what point should I notify you of side effects?
- Should I drink more or less fluid when taking a diuretic?
- What should I do if I miss a dose or take too much?
- Should I add salt to my food while taking diuretics?