Lasix is the brand name of a prescription tablet that treats fluid retention (edema) due to congestive heart failure, cirrhosis of the liver, or kidney disease. Lasix is also used to lower blood pressure in people with high blood pressure (hypertension) and, frequently, with kidney problems, as well.

The active ingredient in Lasix, furosemide, is a loop diuretic (“water pill”) that increases the body’s elimination of water and salt, reducing excess fluids from the body’s tissues and lowering blood pressure. Like all diuretics, Lasix can cause side effects and interact with other drugs. A careful review of the pros and cons of taking Lasix is a vital first step in deciding to start treatment.

RELATED: Learn more about Lasix

Common side effects of Lasix

Lasix’s most common side effects include:

Frequent urination
Low electrolyte levels
Dizziness
Vertigo
Nausea
Vomiting
Diarrhea
Constipation
Irritation of the mouth or stomach
Abdominal cramps
Loss of appetite
Sudden drop in blood pressure when standing up (orthostatic hypotension)
Muscle cramps or muscle pain
Weakness
Numbness
Ringing in the ears (tinnitus)
Headache
Blurred vision
Changes in color vision
Restlessness
Elevated blood sugar levels
Elevated cholesterol and fats in the blood
Excess uric acid
Sugar in the urine
Increased liver enzymes
Allergic reactions such as skin rash, hives, itching, or sensitivity to light

Serious side effects of Lasix

Like all water pills, Lasix has several serious and potentially severe side effects including:

Dehydration
Severe electrolyte depletion
Low potassium levels in the blood
Low blood volume
Jaundice
Elevated blood pH
Loss of hearing
Decline or loss of brain function due to liver dysfunction
Swelling of the pancreas
Blood disorders
Severe allergic reactions

How long do Lasix side effects last?

Most minor adverse effects are temporary and wear off in about six to eight hours after taking the dose of Lasix. Other common side effects may take longer to resolve such as dehydration, electrolyte imbalance, elevated blood sugar, or high cholesterol.

Serious side effects may require treatment and take several days to resolve. Swelling of the pancreas or blood disorders such as anemia (low blood cell counts) may require days or weeks to resolve. Hearing loss and tinnitus are serious side effects that are typically temporary. However, there is a rare chance of permanent hearing loss in those using other medications that are toxic to the ears or with reduced kidney function. Circulatory collapse due to severe dehydration or coma due to liver dysfunction are potentially life-threatening and will require intensive hospital care.

Lasix contraindications & warnings

Like all prescription drugs, Lasix may be restricted or avoided completely in some people with certain medical conditions. Misusing or taking too much Lasix can also create problems.

Abuse and dependence

Lasix is not a drug that causes dependence nor is it commonly abused or misused outside of competitive athletics. Withdrawal symptoms, however, are possible when Lasix is discontinued. When Lasix is no longer taken, the body sometimes overcompensates by retaining too much water and salt. As a result, fluid builds up in the body’s tissues and bloodstream, causing rebound edema and high blood pressure for a few days. While generally harmless, people with heart disease or heart failure will require observation and monitoring after Lasix treatment ends. To avoid this rebound effect, healthcare providers may gradually reduce the Lasix dose to discontinuation or place the patient on a low-sodium diet.

Overdose

The maximum daily dose for Lasix tablets is 600 mg. A Lasix overdose can produce severe dehydration, low blood volume, low potassium, and severe electrolyte depletion. Symptoms of an overdose include extreme thirst, extreme weakness, heavy sweating, hot or dry skin, muscle pains or cramps, changes in heartbeat, nausea, vomiting, and fainting. If too much Lasix has been taken, emergency medical care is required.

Restrictions

All people taking Lasix will be monitored for signs of:

Dehydration symptoms such as dry mouth, thirst, weakness, muscle cramps, and digestive system problems
Low potassium levels
Low sodium levels
Low magnesium levels
Low calcium levels
Alkaline blood
High blood sugar

Lasix is contraindicated (prohibited) for use in people with:

Anuria, that is, “no urine,” caused when the kidneys no longer produce urine
Severe allergic reactions to furosemide or the inactive ingredients in Lasix

People with certain medical conditions may require a restricted dose or close monitoring for side effects:

Premature newborns can get kidney stones or calcium deposits in the kidneys
People older than 65 could be started at the lowest possible dose and monitored for dehydration, electrolyte imbalance, circulation problems (such as blood clots), or kidney problems
People with kidney or liver disease will be monitored closely and may receive lower doses
Blood sugar levels may go up in people with diabetes
People with severe urinary retention problems, such as enlarged prostate or a narrow urethra, may experience a significant worsening of their symptoms. They will require close monitoring in the first few days.
Gout could worsen when taking Lasix
In people with nephrotic syndrome, Lasix may be less effective and more likely to cause hearing problems
Lupus could activate or worsen when taking Lasix

Ask a doctor or other healthcare professional about the risks and benefits of taking Lasix while pregnant or breastfeeding. It is recommended that Lasix should only be used in pregnant women if the potential benefits outweigh the risk to their unborn child because the overall safety is not completely known. I Lasix reduces lactation for nursing mothers and appears in breast milk, so this medication is often avoided in these women.

Lasix interactions

Because of possible drug interactions, Lasix should not be taken with certain types of drugs. Some medications should never be combined with Lasix and other medications should try to be avoided, but several types of drugs will require caution and possible dose adjustments when taken with Lasix.

Two drugs are never combined with Lasix:

Desmopressin
Marplan (isocarboxazid)

Because of the risk of dehydration, electrolyte imbalances, kidney damage, or circulatory collapse, drugs to be avoided or used cautiously with Lasix include:

Diuretics
Laxatives
Corticosteroids
Proton-pump inhibitors
Bronchodilators (beta-2 agonists)

Medications that can affect blood pressure such as:

Sedatives
Barbiturates
Opioid pain relievers
Antipsychotic medications
Erectile dysfunction medications
Stimulants (including caffeine)
ADHD medications
Wakefulness agents
Antidepressants
Corticosteroids
Migraine medications (triptans and ergots)

Finally, other medications to avoid or use cautiously are:

Aminoglycoside antibiotics
Certain cancer drugs
NSAIDs (nonsteroidal anti-inflammatory drugs)
Quinine-based drugs
Bile acid sequestrants (used to treat high cholesterol)
Certain seizure medications
Certain diabetes medications
Methotrexate
Lithium

How to avoid Lasix side effects

People taking Lasix or any other diuretic may experience unwanted side effects. As a tablet, people generally take Lasix every day, sometimes for a prolonged period. A few safety guidelines can help maximize its benefits while minimizing the risk of side effects.

1. Take Lasix as directed

Follow all the directions given by a healthcare provider or printed on the prescription label. The standard dose is 40–120 mg per day for edema and 10-40 mg twice daily for hypertension. If the dose is divided into two daily doses, do not skip a dose or combine two doses into one. Do not take more or less than prescribed until consulting with a doctor or healthcare professional.

2. Tell the doctor about all medical conditions and medications

Many medical conditions and drugs can affect the safety of taking Lasix, so make sure the prescribing doctor or healthcare professional is well-informed about:

All current medical conditions, particularly kidney disease, liver disease, urination problems, low blood pressure, diabetes, gout, lupus, electrolyte problems, or allergies to sulfonamides (sulfa drugs)
Pregnancy, breastfeeding, or plans to get pregnant
Any upcoming surgery or surgery planned for the future
Glucose blood tests that are coming up
Any planned MRI or medical scan that will include radioactive contrast dyes
All over-the-counter and prescription drugs, supplements, and herbal remedies being taken, particularly desmopressin or Marplan (isocarboxazid)

3. Watch for signs of dehydration or electrolyte imbalance

A doctor or healthcare provider will explain how much and what kind of fluids to take after a dose of Lasix. These may be restricted to ensure the success of the therapy. Still, watch for signs of severe dehydration or electrolyte depletion. These include:

Dry mouth
Dry eyes
Muscle cramps
Drowsiness
Fatigue
Weakness
Irregular heartbeat
Fast heartbeat

If fluids are not restricted, immediately take fluids at signs of dehydration. If fluids are restricted, call a healthcare provider for medical advice.

To avoid electrolyte imbalances, people will often be prescribed potassium supplementation such as Klor-Con. Additionally, healthcare providers may recommend changes in a person’s diet to increase the amount of potassium.

Use extra caution on hot summer days, as people are more likely to get dehydrated and lose electrolytes. People can either avoid or limit their time spent outdoors on hot days and always carry a water bottle. Since some people can become more sensitive to sunlight while taking Lasix, it’s good to be cautious of sunny days and wear sunscreen or protective clothing.

4. Keep all follow-up appointments and frequently monitor self at home

To avoid some of the more serious side effects, make sure that all appointments are kept and necessary tests are taken. The purpose of these tests and visits is partly to monitor any adverse effects before they become serious medical problems. Some people with pre-existing medical conditions may be asked to regularly monitor body weight, blood pressure, or blood sugar. Check these values faithfully with store-bought bathroom scales, blood pressure cuffs, or blood glucose testers. Record the values and show them to the doctor during office visits. Depending on the pre-existing condition, people taking Lasix should make sure to discuss with a doctor their goal blood pressure range, ideal blood sugar range or how much weight they can gain or lose.

5. Plan your activities around the dosing schedule

A healthcare professional may ask that Lasix always be taken at a certain time of day. Remember: frequent urination is the most common effect of taking Lasix. It’s a good idea to delay certain activities for at least four to six hours after a dose is taken. Some people may not be put on a strict schedule. In that case, the dose can be taken at a time more convenient to the day’s activities.

6. Avoid taking a late dose

Taken too late in the day, Lasix may make it hard to sleep because of running to the bathroom frequently. Most healthcare professionals will advise people not to take Lasix after a certain time, like 4 P.M. Ask a doctor, pharmacist, or another healthcare provider how late in the day Lasix can be taken without ruining a good night’s sleep.

7. Avoid some common over-the-counter drugs

Popular pain-relievers (NSAIDs), such as ibuprofen (Advil, Motrin) and naproxen (Aleve), can reduce the effectiveness of Lasix and increase the risks to the kidney or ears. Also, over-the-counter (OTC) laxatives, such as Miralax and magnesium citrate, increase the risk of dehydration and electrolyte depletion. Ask a doctor or other healthcare provider about alternatives to commonly used OTC drugs when taking Lasix.

Lasix side effects and how to avoid them