Lasix (Furosemide) - Oral: Uses, Side Effects, Dosages, Interactions

What Is Lasix?

Lasix (furosemide) contains furosemide, which belongs to the loop diuretic (water pill) drug class. Furosemide helps your body get rid of salt and water by preventing your kidneys from reabsorbing them. It increases the amount of urine in your body, which helps lower your blood pressure and reduce swelling.

Lasix is a prescription medicine and can be used in combination with other drugs. It's available as a tablet and as a solution.

Drug Facts

Generic Name: Furosemide

Brand Name(s): Lasix

Drug Availability: Prescription

Therapeutic Classification: Loop diuretic

Available Generically: Yes

Controlled Substance: N/A

Administration Route: Oral

Active Ingredient: Furosemide

Dosage Form(s): Tablet, solution, injection

What Is Lasix Used For?

Lasix is used alone or in combination therapy to treat hypertension (high blood pressure). Persistently high blood pressure can cause damage to the brain, heart, kidney, and other organs. Lowering high blood pressure helps prevent medical conditions such as strokes, heart attacks, kidney problems, vision loss, and other problems.

Lasix is also used to treat edema (swelling due to fluid buildup in the body) caused by heart failure, liver cirrhosis, and kidney disease, including nephrotic disease. This can reduce shortness of breath and swelling in the arms, legs, and abdomen.

Verywell / Zoe Hansen

How to Take Lasix

Follow the guidelines on the prescription label and ask your healthcare provider if you don't understand anything. 

Lasix is available as an oral tablet and an oral solution (liquid) to take by mouth. It is usually prescribed one or two times a day. When used to treat edema, Lasix may be taken daily or only on particular days of the week. When used to treat high blood pressure, take furosemide around the same time(s) every day to avoid missing a dose. 

Take furosemide exactly as prescribed by your healthcare provider. Take your evening dose a few hours before going to bed to avoid increased urination during the night. Do not take more, less, or more often than prescribed by your healthcare provider.

If taking an oral solution, use the dose-measuring device provided with the medicine. Do not use a household spoon, leading to an inaccurate dose measurement. If you take Carafate (sucralfate), take it two hours before or after you take Lasix.

Lasix helps control high blood pressure and edema, but it does not cure these conditions. Continue to take your medicine even if you feel well. Please do not stop taking it without talking to your healthcare provider.

Storage

Store Lasix at room temperature away from direct light, heat, and moisture. Do not freeze the oral solution. Keep all medicines out of sight and reach of children and pets, ideally locked in a cabinet or closet. 

Unneeded medications should be disposed of properly. Do not flush the medicines down the toilet or throw them in the trash. The best way to dispose of unwanted medication is through a medicine take-back program. Contact your pharmacist or local waste disposal department to learn about medicine take-back programs in your community.

If you plan to travel with Lasix, get familiar with your final destination's regulations. In general, be sure to make a copy of your Lasix prescription. If possible, keep your medication in its original container from your pharmacy with your name on the label. If you have any questions about traveling with your medicine, ask your pharmacist or healthcare provider.

How Long Does Lasix Take to Work?

Lasix starts working and increases urine production within one hour of taking it. The peak diuretic effect occurs within the first or second hour and then reduces over the next six to eight hours.

Off-Label Uses

This medicine may be prescribed for other conditions. Ask your healthcare provider for information.

What Are the Side Effects of Lasix?

This is not a complete list of side effects and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the Food and Drug Administration (FDA) at fda.gov/medwatch or 800-FDA-1088.

Common Side Effects

Common furosemide side effects may include:

Call your healthcare provider if any side effects become severe or do not go away.

Severe Side Effects

Some side effects can be severe. If you have any of these symptoms, call your healthcare provider immediately or seek emergency medical treatment:

Blisters or peeling skin
Blood in urine or stools
Difficulty breathing or swallowing
Dry mouth
Electrolyte imbalance
Fever or chills
Hearing loss or ringing in the ears
Irregular heartbeat
Muscle pain or weakness, cramps
Skin rash
Stomach upset, pain, or nausea
Swollen lymph nodes
Tingling or numbness in the hands or feet
Unusually weak or tired
Vomiting or diarrhea
Yellowing of the skin or eyes

Long-Term Side Effects

High doses of Lasix may cause irreversible hearing loss.

Report Side Effects

Lasix may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Lasix Should I Take?

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

For oral dosage forms (oral solution or tablets):
- For edema:
  - Adults—At first, 20 to 80 milligrams (mg) once a day as a single dose or divided and given twice per day. Your doctor may adjust your dose as needed.
  - Children—Dose is based on body weight and must be determined by your doctor. The starting dose is usually 2 milligrams (mg) per kilogram (kg) of body weight per day as a single dose. Your doctor may adjust your dose as needed. However, the dose is usually not more than 6 mg per kg of body weight per day.
- For high blood pressure:
  - Adults—At first, 40 milligrams (mg) two times per day. Your doctor may adjust your dose as needed.
  - Children—Use and dose must be determined by your doctor.

Modifications

The following modifications (changes) should be kept in mind when using Lasix:

Severe allergic reaction: Avoid using Lasix if you have a known allergy to it or any of its ingredients.

Pregnancy: In animal studies, Lasix caused fetal death. We don't know enough about the safety and effectiveness of Lasix in pregnant people and on their unborn fetus. Lasix should only be used during pregnancy if the benefits outweigh the risks.

Breastfeeding: Lasix is present in breastmilk. It also can inhibit breastmilk. Caution should be used when using Lasix during breastfeeding. Talk with your healthcare provider if you plan to breastfeed, to weigh the benefits and risks of taking Lasix while nursing and the different ways to feed your baby.

Adults over the age of 65 years: Clinical studies haven't included a large enough number of people in this age group to see whether they respond differently from younger adults. It may be that some adults over 65 may have different kidney function, and their labs may need to be closely monitored during treatment with Lasix.

Children: Lasix has caused heart and kidney side effects in premature infants and young children. Caution should be used and kidney and heart function should be closely monitored.

Other modifications: Individuals with kidney problems may not be able to clear medications from their bodies as easily. This means the medicine stays in the body longer and can have increased side effects. For this reason, if you have severe kidney impairment, your healthcare provider will likely monitor your kidney function closely while on Lasix.

Missed Dose

If you accidentally forgot your Lasix dose, take it as soon as you remember. If it's already close to your next scheduled dose, however, then skip the missed dose and take the following dose at your next scheduled dosing time. Don't try to double up to make up for the missed dose.

Try to find ways that work for you to help yourself remember to routinely take your medication. If you miss too many doses, Lasix might be less effective at treating your condition.

Overdose: What Happens If I Take Too Much Lasix?

The symptoms of a suspected overdose of Lasix include:

Feeling very thirsty or hot
Heavy sweating
Hot and dry skin
Extreme weakness or fainting.

If you think that you're experiencing an overdose or life-threatening symptoms, however, seek immediate medical attention.

What Happens If I Overdose on Lasix?

If you think you or someone else may have overdosed on Lasix, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Lasix, call 911 immediately.

Precautions

It is very important that your doctor check the progress of you or your child at regular visits to make sure this medicine is working properly. Blood or urine tests may be needed to check for unwanted effects.

Using this medicine while you are pregnant may cause your unborn baby to be bigger than normal. If you think you have become pregnant while using this medicine, tell your doctor right away.

This medicine may cause you or your child to lose more potassium from your body than normal (hypokalemia). This is more likely to occur if you have liver disease (e.g., cirrhosis), or if you are using this medicine together with steroids (cortisone-like medicines), adrenocorticotropic hormone (ACTH), large amounts of licorice, or laxatives for a long time. Tell your doctor if you become sick with severe or continuing nausea, vomiting, or diarrhea, and drink fluids to prevent getting dehydrated. Check with your doctor right away if you have dry mouth, increased thirst, muscle cramps, or nausea or vomiting.

Dizziness, lightheadedness, or fainting may occur, especially when you get up suddenly from a lying or sitting position. Getting up slowly may help. If the problem continues or gets worse, check with your doctor.

Stop using this medicine and check with your doctor right away if you have a sudden decrease in hearing or loss of hearing. You may also have dizziness or ringing in the ears. Tell your doctor if you have a feeling of constant movement of self or surroundings or a sensation of spinning.

This medicine may cause an increase in blood sugar levels. If you are diabetic and notice a change in the results of your blood or urine sugar tests, check with your doctor.

This medicine may make your skin more sensitive to sunlight. Use a sunscreen, hat, and protective clothing when you are outdoors. Avoid sunlamps and tanning beds.

Make sure any doctor or dentist who treats you knows that you are using this medicine. This medicine may affect the results of certain medical tests.

Do not take other medicines unless they have been discussed with your doctor. This especially includes prescription or nonprescription (over-the-counter) medicines for appetite control, asthma, colds, cough, hay fever, or sinus problems.

What Are Reasons I Shouldn't Take Lasix?

Lasix is contraindicated in anuria (when the kidneys stop producing urine) or hypersensitivity to furosemide or any other ingredient of the tablet or solution. If you're allergic to Lasix or any of its ingredients, avoid using it. Ask your pharmacist or healthcare provider for a full list of the ingredients if you're unsure.

What Other Medications Interact With Lasix?

Use caution when taking Lasix with the following medications:

Aminoglycoside antibiotics such as:

Amikacin
Garamycin (gentamicin)
Tobi (tobramycin)

Taking Lasix with other blood pressure drugs, such as angiotensin enzyme inhibitors (ACE inhibitors) or angiotensin receptor blockers (ARBs), can cause a dangerous drop in blood pressure. These include drugs such as:

Lotensin (benazepril)
Zestril (lisinopril)
Vasotec (enalapril)
Capoten (captopril)
Univasc (moexipril)
Aceon (perindopril)
Accupril (quinapril )
Altace (ramipril)
Edarbi (azilsartan)
Atacand (candesartan)
Exforge (valsartan and amlodipine)
Diovan (valsartan)
Others

Furosemide can increase nonsteroidal anti-inflammatory drug (NSAID) levels in your body. It can increase the risk of dangerous side effects. NSAIDs include:

Barbiturates such as Phenobarbital.

Corticosteroids such as:

Celestone (betamethasone)
Entocort (budesonide)
Dexasone (dexamethasone)
Cortef (hydrocortisone)
Medrol (methylprednisolone)
Prelone (prednisolone)

Others:

Platinol (cisplatin)
Neoral (cyclosporine)
Lanoxin (digoxin)
Edecrin (ethacrynic acid)
Lithobid (lithium)
Medications for diabetes
Probenecid
Phenytek (phenytoin)

For more detailed information about medication interactions with Lasix, talk with your pharmacist or healthcare provider.

And be sure to talk with your healthcare provider about any other medicines that you take or plan to take, including over-the-counter, nonprescription products, vitamins, herbs, or plant-based medicines.

What Medications Are Similar?

Diuretics are one of the most common types of blood pressure medications. Diuretics are commonly known as "water pills" and treat several conditions, including hypertension (high blood pressure), heart failure, and kidney problems. There are various classes of diuretics, such as thiazide, loop, and potassium-sparing diuretics. 

Thiazide diuretics treat blood pressure and eliminate excess fluid, or edema, in people with heart failure, liver disease, steroid use, and estrogen-replacement therapy.

Some common thiazide diuretics include:

Microzide (hydrochlorothiazide)
Indapamide
Diuril (Chlorothiazide)
Mykrox (metolazone)
Chlorthalidone

Loop diuretics treat edema in congestive heart failure and kidney and liver disease. They work by blocking the reabsorption of fluid that passes through your kidneys. In addition to Lasix, these include drugs such as:

Bumex (bumetanide)
Demadex (torsemide)
Edecrin (ethacrynic acid)

Potassium-sparing diuretics maintain the potassium balance in the body. These drugs don't lower blood pressure significantly when used alone. Potassium-sparing diuretics include:

Aldactone (spironolactone)
Midamor (amiloride)
Dyrenium (triamterene)

The choice of a particular diuretic depends on the person's condition. Your healthcare provider will prescribe the best suitable drug.

Frequently Asked Questions

Lasix is used to treat hypertension (high blood pressure) and edema (extra fluid in the body) due to other conditions such as heart failure, liver disease, and kidney disease.
Lasix works on the kidneys and increases urine flow to help get rid of extra salt and water from the body.
Furosemide may interact with certain drugs such as aminoglycoside antibiotics, ACE inhibitors, ABR drugs, laxatives, lithium, cisplatin, cyclosporine, nonsteroidal anti-inflammatory drugs (NSAIDs), methotrexate, phenytoin, and others.
Lasix may cause common side effects such as dehydration, constipation, frequent urination, and electrolyte imbalance. Contact your healthcare provider if you have serious side effects such as muscle cramps, weakness, confusion, severe dizziness, fainting, extreme thirst, and irregular heartbeat.

How Can I Stay Healthy While Taking Lasix?

Diuretics are a medication of choice for treating high blood pressure and other problems caused by fluid accumulation in the body. However, they may cause a few side effects, such as dehydration and severe electrolyte loss. It's essential to follow all your healthcare provider's dietary and medical instructions. A healthy lifestyle and treatment with a diuretic may help you ease off the symptoms of high blood pressure.

Your healthcare provider may prescribe a low-salt diet or increased amounts of potassium-rich foods. Consider working with a registered dietitian nutritionist (RD or RDN) that specializes in heart or kidney health to help you achieve your nutrition goals while on Lasix. RDs can help you navigate a lower salt diet (like the DASH Diet), tips for kidney and heart health, and more.

Other suggestions include but are not limited to:

Take your diuretic in the morning or a few hours before bed to minimize nighttime trips to the bathroom.
Keep yourself hydrated and limit alcohol intake.
Monitor your blood pressure, electrolytes level, and kidney function through regular appointments to get the most out of Lasix treatment.
Avoid getting up too fast from a stationary position, or you may feel dizzy.
Pregnant and breastfeeding mothers may need to avoid Lasix.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some drug content, as indicated on the page.

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