Buy Lasix (Furosemide) — Online Prescription
Furosemide — the "water pill" — is a prescription-only loop diuretic in the United States. Here's what it treats, why potassium monitoring matters, how it compares to other diuretics, and what your options are if cost is the real obstacle.
Medically reviewed Medically reviewed by Darcey Melnyk, Pharmacist — NPI 1740713718 · Last updated 2026-08-31
| Active ingredient | Furosemide |
|---|---|
| Dosage form | Tablet, oral solution, injection |
| Administration route | Oral, intravenous, intramuscular |
Class: Loop Diuretic [EPC]
Indications: INDICATIONS AND USAGE Edema Furosemide tablets are indicated in adults and pediatric patients for the treatment of edema associated with congestive heart failure, cirrhosis of the liver, and renal disease, including the nephrotic syndrome. Furosemide tablets are particularly useful when an agent with greater diuretic potential is desired. Hypertension Oral furosemide may be used in adults for the treatment of hypertension alone or in combination with other antihypertensive agents. Hypertensive p…
Contraindications: CONTRAINDICATIONS Furosemide tablets are contraindicated in patients with anuria and in patients with a history of hypersensitivity to furosemide.
openFDA label data — Updated 2026-09-02Lasix (furosemide) — the "water pill" — is prescription-only in the US in every form: tablet, oral solution, and injection. It's a loop diuretic used for fluid overload from heart failure, kidney disease, and liver disease, and it requires bloodwork to monitor potassium and kidney function. It's also one of the least expensive prescription drugs available — cost usually isn't the real barrier.
What furosemide treats, and how it works
Furosemide is a loop diuretic — it acts on a specific part of the kidney (the loop of Henle) to block reabsorption of sodium and chloride, causing the kidneys to remove significantly more salt and water than they otherwise would. That's the mechanism behind its nickname, the "water pill."
It's FDA-approved to treat edema (fluid buildup) associated with:
- Congestive heart failure
- Cirrhosis of the liver
- Kidney disease, including nephrotic syndrome
It's also approved for hypertension, usually alongside other blood pressure medications rather than as a first-choice standalone treatment for routine high blood pressure.
Dosing and forms
| Form | Typical strengths | Onset |
|---|---|---|
| Oral tablet | 20 mg, 40 mg, 80 mg | ~30–60 minutes |
| Oral solution | 10 mg/mL, 40 mg/5mL | ~30–60 minutes |
| IV/IM injection | 10 mg/mL | Within minutes |
Dosing is individualized — there's no single "standard" dose. Your prescriber sets and adjusts it based on your condition, kidney function, and bloodwork, and may increase or decrease it over time. Never change your own dose or skip doses without talking to your prescriber first, even if your symptoms improve.
Furosemide vs. bumetanide vs. torsemide
These three loop diuretics all work the same way, but a prescriber may choose one over another based on how consistently your body absorbs it or how it fits your situation:
| Furosemide (Lasix) | Bumetanide (Bumex) | Torsemide (Demadex, Soaanz) | |
|---|---|---|---|
| Relative potency | Baseline | ~40x more potent by weight | ~2–4x more potent by weight |
| Oral absorption | More variable between patients | More consistent | More consistent, longer-acting |
| Generic available | Yes | Yes | Yes |
Switching between these isn't a simple milligram-for-milligram swap — the conversion ratios differ, and only your prescriber should make that change, typically starting with a conservative dose and adjusting based on response.
Potassium, electrolytes, and monitoring
This is the most important safety information about furosemide, and it's exactly why it's prescription-only rather than available over the counter:
Furosemide causes your kidneys to excrete potassium along with sodium and water. Low potassium (hypokalemia) can cause muscle cramps, weakness, and — in more serious cases — dangerous heart rhythm changes. Your prescriber will typically order periodic bloodwork to monitor potassium, sodium, and kidney function, and may prescribe a potassium supplement or add a potassium-sparing medication depending on your levels.
Furosemide is contraindicated in patients with anuria (inability to produce urine) and in anyone with a known hypersensitivity to the drug. Dehydration and low blood pressure are also possible, especially at higher doses — contact your prescriber if you feel unusually dizzy, lightheaded, or notice a significant drop in how much you're urinating.
If cost is the real issue
Most people searching for furosemide "without a prescription" are actually trying to avoid the cost of a doctor's visit or the medication itself. On both counts, furosemide is one of the more accessible prescription drugs available:
- The drug itself is inexpensive. According to CMS's National Average Drug Acquisition Cost data, generic furosemide 40 mg tablets cost pharmacies roughly $0.03 per tablet — among the least expensive prescription drugs on the market. Ask your pharmacist for the cash price; it's often lower than an insurance copay.
- A prescription doesn't require a specialist. Any primary care provider, urgent care clinic, or telehealth visit can evaluate and prescribe furosemide when it's appropriate.
- We can transfer or fill a new prescription quickly. Call us at (860) 522-9289 once you have a prescription, or ask us about coordinating with your prescriber's office.
If a website offers to sell you furosemide "without a prescription," that's a red flag for a rogue or unlicensed online pharmacy — see our guide on evaluating online pharmacies for how to check legitimacy before ordering medication from anywhere online.
Shortage reported — Affects: Furosemide, Injection, 20 mg/2 mL (NDC 55150-322-25). If that's not the oral form you take, ask your pharmacist whether your specific product is affected.
FDA openFDA — Updated 2026-09-02National Average Drug Acquisition Cost (NADAC): $0.033 per tablet (FUROSEMIDE 40 MG TABLET). This is the average price pharmacies pay wholesalers — not your out-of-pocket cost — published by CMS for pricing transparency.
CMS NADAC — Updated 2026-09-02Lasix (Furosemide) Prices in the USA
| Dosage | Brand-name avg. price | Generic avg. price |
|---|---|---|
| 20 mg | $40–70 / 30 tablets | $8–15 / 30 tablets |
| 40 mg | $45–90 / 30 tablets | $8–18 / 30 tablets |
| 80 mg | $60–110 / 30 tablets | $12–25 / 30 tablets |
Frequently asked questions
Can I buy Lasix (furosemide) over the counter in the US?
No. Furosemide is available only by prescription in the United States, in tablet, oral solution, and injectable forms. No dose is FDA-approved for over-the-counter sale, because it requires monitoring of kidney function, blood pressure, and electrolyte levels that a pharmacist or physician needs to oversee.
Why is furosemide called a "water pill"?
It's a common nickname for diuretics generally — furosemide makes your kidneys remove more salt and water than they otherwise would, which increases urination and reduces fluid buildup (edema) from conditions like heart failure, kidney disease, or liver cirrhosis. "Water pill" describes the effect, not a different or milder drug.
Does Lasix lower blood pressure?
It can, as a side effect of removing excess fluid, but it isn't typically a first-choice blood pressure medication on its own — other diuretics (like hydrochlorothiazide) or other drug classes are more commonly used for routine hypertension. Furosemide's main jobs are treating fluid overload from heart failure, kidney disease, and liver disease; blood pressure reduction is often secondary to that.
What's the maximum dose of Lasix in 24 hours?
There isn't one universal number — dosing is individualized based on your condition, kidney function, and response, and can range from a single low dose to much higher doses in a hospital setting for severe fluid overload. Never adjust your own dose; your prescriber sets and changes it based on your bloodwork and symptoms.
Why does furosemide affect potassium levels?
As a loop diuretic, furosemide causes the kidneys to excrete potassium along with sodium and water, which can lead to low potassium (hypokalemia) — a real risk that can cause muscle cramps, weakness, or dangerous heart rhythm changes if unmonitored. This is exactly why furosemide requires prescriber oversight and periodic bloodwork, and why some patients are prescribed a potassium supplement or a potassium-sparing medication alongside it.
How is furosemide different from bumetanide (Bumex) or torsemide (Demadex)?
All three are loop diuretics that work the same way, but they differ in potency and how completely the body absorbs them when taken orally — furosemide's absorption is more variable between patients, which is part of why a prescriber might switch you to bumetanide or torsemide if furosemide isn't working consistently. See the comparison table below; dose conversion between them is not a simple 1:1 swap and should only be done by your prescriber.
How long does it take for Lasix to start working?
Oral furosemide typically starts working within about an hour, with peak effect around 1–2 hours; IV furosemide works within minutes, which is why it's used for urgent fluid overload in a hospital setting. How long the effect lasts varies by dose and individual kidney function.
What should I do if I can't afford my furosemide prescription?
Furosemide is one of the least expensive prescription medications available — generic tablets have a national average acquisition cost of only a few cents each. Ask your Arrow Pharmacy pharmacist about the cash price before assuming you can't afford it, and ask about patient assistance programs if you're still struggling.
Sources
- Furosemide — FDA-approved prescribing information (label) — U.S. Food and Drug Administration
- Furosemide / Lasix price data (average retail cash price) — GoodRx (consumer price reference)
- NADAC (National Average Drug Acquisition Cost) — CMS
- openFDA Drug Shortages — U.S. FDA
- Torsemide (Demadex/Soaanz) — FDA-approved prescribing information — U.S. Food and Drug Administration