Diuretics: Loop, Potassium Sparing, and Thiazide
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Diuretics: Loop, Potassium Sparing, and Thiazide

Type of Medication

Diuretic, often called "water pills".

Medications and Their Commonly Used Brand Names

Generic nameBrand name
Loop diuretics
ethacrynic acidEdecrin
furosemideLasix, Myrosemide
Potassium-sparing diuretics
Thiazide diuretics
chlorthalidoneHygroton, Thalitone
hydrochlorothiazideEsidrix, Hydro-chlor, Hydro-D, HydroDIURIL, Microzide, Oretic
hydroflumethiazideDiucardin, Saluron
methyclothiazideAquatensen, Enduron
metolazoneDiulo, Mykrox, Zaroxolyn
trichlormethiazideMetahydrin, Naqua, Trichlorex
Potassium-sparing and hydrochlorothiazide combination
amiloride and hydrochlorothiazideModuretic
spironolactone and hydrochlorothiazideAldactazide, Spirozide
triamterene and hydrochlorothiazideDyazide, Maxzide

What They Are Prescribed for

  • To reduce the amount of water in the body.
  • To treat high blood pressure (hypertension), especially in people who are believed to have higher blood volumes (African Americans, older people, obese people and patients with kidney problems).
  • To treat congestive heart failure.
  • To treat problems caused by too little potassium in the body (spironolactone and potassium-sparing and hydrochlorothiazide combinations).

How Diuretics Work

Diuretics act on the kidneys to increase the production of urine. Unlike the other types, potassium-sparing diuretics do not cause your body to lose potassium.

Precautions While Taking a Diuretic

See Your Doctor Regularly

It is important that your doctor check your progress at regular visits to allow for dosage adjustments and manage any side effects. Before you have any type of surgery, including dental surgery, emergency treatment, or medical tests, make sure the medical doctor or dentist in charge knows that you are taking a diuretic.

Maintain a Healthy Potassium Level

Thiazide diuretics and especially loop diuretics may cause an excessive loss of potassium from your body. To help prevent this, your doctor may recommend any of the following:

  • Eat or drink foods that have a high potassium content, such as oranges or other citrus fruits and juices
  • Take a potassium supplement
  • Take another medicine to help prevent the loss of potassium

To prevent the loss of too much water and potassium, tell your doctor if you become sick, especially with severe or continuing vomiting or diarrhea.

It is essential to follow your doctor's specific instructions with regard to potassium and dietary changes. Extra potassium may not be necessary and in some cases, too much potassium can be harmful. Potassium-sparing diuretics do not cause a loss of potassium from your body as some other diuretics do. Therefore, if you are taking this type of diuretic, it is not necessary for you to get extra potassium in your diet. Since salt substitutes and low-sodium milk may contain potassium, do not use them unless told to do so by your doctor.

If you are already on a special diet, as in the case of diabetes, it is especially important to consult with your doctor before making any dietary changes.

Do Not Take Diuretics During Pregnancy

Diuretics are generally not useful for treating the normal swelling of hands and feet that can occur with pregnancy. Diuretics should not be taken during pregnancy unless recommended by your doctor. Thiazide diuretics as well as potassium-sparing diuretics and hydrochlorothiazide combinations should not be used during the first month of breast-feeding.

Older Adults, Take Extra Care

Loop diuretics and Thiazide diuretics: Dizziness, lightheadedness, or signs of too much potassium loss are more likely to occur in the elderly; elderly patients are more prone to excessive dehydration and its complications.

Potassium-sparing diuretics: Signs and symptoms of too much potassium are more likely to occur in the elderly.

Manage Your Medications

Tell your doctor about all the medications you take; some should not be taken with diuretics, while others may require a different dosage level. Some common medications that fall under this category include:

  • Angiotensin-converting enzyme (ACE) inhibitors
  • Digoxin (Lanoxin)
  • Lithium (Cibalith-S, Eskalith, Lithane)
  • Cholestyramine (Questran)
  • Colestipol (Colestid)
  • Potassium-containing medicines or supplements

If you are taking any type of diuretic to control high blood pressure, do not take the following types of over-the-counter medications without checking with your doctor:

  • Appetite control
  • Asthma
  • Colds
  • Cough
  • Hay fever
  • Sinus problems

Be Cautious with Certain Medical Conditions

The presence of other medical problems may affect the use of diuretics. Tell your doctor if you have any other medical problems, especially:

  • Diabetes mellitus
  • Gout
  • Hearing problems
  • Pancreatitis (inflammation of the pancreas)
  • Heart attack, recent
  • Kidney disease
  • Liver disease
  • Lupus erythematosus
  • History of kidney stones
  • Menstrual problems or breast enlargement
  • Impotence

Eat a Healthful Diet

Medications are only part of the treatment for high blood pressure. Scientific research has shown that a diet rich in fruits, vegetables, and low-fat dairy products, and one that is low in sodium, can help control blood pressure. Regular exercise, as well as maintaining a healthful weight are also essential lifestyle factors for the management of hypertension.

Don't Ignore Dizziness

When you are taking a diuretic, dizziness, lightheadedness, or fainting may occur, especially when you get up from a lying or sitting position. Getting up slowly may help. Dizziness, lightheadedness, or fainting is also more likely to occur if you drink alcohol, stand for long periods of time, exercise vigorously, or if the weather is hot. If this problem continues or worsens, check with your doctor.

Avoid the Sun

Some diuretics may cause your skin to be more sensitive to sunlight. Exposure to sunlight, even for brief periods of time, may cause a skin rash, itching, redness, or sunburn. When taking this medication, follow these precautions:

  • Stay out of direct sunlight, especially between the hours of 10:00 a.m. and 3:00 p.m., if possible.
  • Wear protective clothing, including a hat and sunglasses.
  • Apply sunscreen and sunblock lip balm with an SPF of at least 15.
  • Do not use a sunlamp or tanning bed or booth.
  • If you have a severe reaction from the sun, tell your doctor.

Don't Stop this Medication without Your Doctor's Approval

It is essential to take your medication even if you feel fine and do not have any symptoms, which is often the case with hypertension. You must continue to take it as directed in order to keep your blood pressure under control. It may be possible to taper off the medication, particularly if you undertake lifestyle measures to lower your blood pressure (i.e., low calorie diet and exercise), but this should be done only under your physician's supervision. If high blood pressure persists without treatment, it can lead to heart attacks, heart failure, blood vessel disease, stroke, kidney failure and/or blindness.

Dosing and Missed Doses

Take each dose at the same time each day. Since diuretics work by increasing the amount of urine you produce, the timing of when you take your medication may help keep the increased urination from disrupting your sleep:

  • If you take a single dose, take it after breakfast
  • If you take more than one dose, take the last dose no later than 6:00 p.m., unless otherwise directed by your doctor

If your diuretic upsets your stomach, it may be taken with meals or milk. If stomach upset continues or gets worse, or if you suddenly get severe diarrhea, check with your doctor.

If you miss a dose of your diuretic, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Possible Side Effects

The side effects listed here are most commonly encountered with at least one type of diuretic drug, not necessarily all of them. However, since many of the effects of diuretics are similar, these side affects may occur with any one of these medicines, although they may be more common with some than with others.

Check with your doctor as soon as possible if any of the following side effects occur.

From Excessive Dehydration:

  • Extreme tiredness, which should subside as your body adapts to the medicine
  • Lightheadedness, dizziness or loss of consciousness
  • Diminishing urination
  • Dryness of the mouth and extreme thirst

From Excessive Potassium Loss:

  • Dryness of mouth
  • Increased thirst
  • Irregular heartbeat
  • Mood or mental changes
  • Muscle cramps or pain
  • Nausea or vomiting
  • Unusual tiredness or weakness
  • Weak pulse

From too Much Potassium:

  • Confusion
  • Irregular heartbeat
  • Nervousness
  • Numbness or tingling in hands, feet, or lips
  • Shortness of breath or difficulty breathing
  • Unusual tiredness or weakness
  • Weakness or heaviness of legs

From Excessive Sodium Loss:

  • Confusion
  • Convulsions
  • Decreased mental activity
  • Irritability
  • Muscle cramps
  • Unusual tiredness or weakness

Check with your doctor if any of the following side effects occur frequently and/or become bothersome.

  • Loss of appetite
  • Nausea and vomiting
  • Stomach cramps and diarrhea
  • Constipation
  • Sunburn
  • Impotence

There are also many less common side effects that have been reported with diuretic use. If you develop any new symptoms after starting these medications, consult your doctor.

Other Uses for Diuretics:

Although the uses listed below are not included on the product label, diuretics may be used to treat certain other conditions.

Loop Diuretics:

  • Hypercalcemia (too much calcium in the blood)
  • Diagnostic aid for kidney disease


  • Polycystic ovary syndrome
  • Hirsutism in women (excessive body and facial hair growth)

Thiazide Diuretics:

  • Diabetes insipidus (water diabetes)
  • Kidney stones (calcium containing)


American Academy of Family Physicians

USP Drug Information


Canadian Family Physician

Canadian Pharmacists Association


USP Drug Information Database. Available at: http://www.usp.org/

Last reviewed February 2008 by Miguel Antelo, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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