What Is Tamiflu?

Tamiflu is the brand name for Oseltamivir Phosphate, a prescription antiviral medication used to treat and prevent influenza (the flu). It belongs to a class of drugs called neuraminidase inhibitors, which work by stopping the flu virus from spreading inside your body.

Manufactured by Genentech (a member of the Roche Group), Tamiflu has been one of the most widely prescribed flu treatments since its FDA approval. Generic versions of Oseltamivir are also available from multiple manufacturers, making the medication more accessible and affordable.

Tamiflu is not an antibiotic (it doesn't treat bacterial infections), and it's not a substitute for the annual flu vaccine. It's a targeted antiviral that specifically fights influenza A and B viruses.

What Is Tamiflu Used For?

Tamiflu has two FDA-approved uses:

1. Treatment of Influenza

Tamiflu is approved for treating acute, uncomplicated influenza A and B in patients 2 weeks of age and older who have been symptomatic for no more than 48 hours. When started early, Tamiflu can:

• Reduce the duration of flu symptoms by 1-2 days
• Decrease the severity of symptoms
• Lower the risk of complications like pneumonia, especially in high-risk patients

2. Prevention (Prophylaxis) of Influenza

Tamiflu is also approved for preventing influenza in patients 1 year of age and older. This is commonly used when:

• A household member has been diagnosed with the flu
• There's a flu outbreak in a nursing home or institutional setting
• A high-risk individual has been exposed to someone with the flu

Tamiflu is sometimes used off-label for extended treatment courses in immunocompromised patients and for treatment of avian influenza strains (H5N1, H7N9).

How Does Tamiflu Work?

Tamiflu is a prodrug — meaning it's converted into its active form (Oseltamivir carboxylate) after you take it. The active form blocks an enzyme called neuraminidase on the surface of influenza viruses. This enzyme is essential for the virus to release copies of itself from infected cells and spread to new cells.

By blocking neuraminidase, Tamiflu traps new virus particles inside infected cells, slowing the spread of infection and giving your immune system a chance to fight back. For a deeper dive, read our guide on how Tamiflu works.

Tamiflu Dosage Guide

Tamiflu dosing depends on the patient's age, weight, kidney function, and whether the medication is being used for treatment or prevention.

Treatment Dosage (Adults and Children ≥40 kg)

• Dose: 75 mg twice daily
• Duration: 5 days
• Timing: Start within 48 hours of first flu symptoms

Treatment Dosage (Children by Weight)

• ≤15 kg: 30 mg twice daily for 5 days
• 15.1-23 kg: 45 mg twice daily for 5 days
• 23.1-40 kg: 60 mg twice daily for 5 days
• >40 kg: 75 mg twice daily for 5 days

Prevention Dosage (Adults and Adolescents ≥40 kg)

• Dose: 75 mg once daily
• Duration: 10 days after household exposure, or up to 6 weeks during community outbreaks

Dose Adjustments

Patients with moderate kidney impairment (creatinine clearance 30-60 mL/min) require a reduced dose. Your doctor will adjust the dosage accordingly. Always take Tamiflu exactly as prescribed.

Available Forms

Tamiflu comes in two forms:

• Oral capsules: 30 mg, 45 mg, and 75 mg
• Oral suspension (liquid): 6 mg/mL powder for reconstitution

The liquid form is ideal for children or anyone who has difficulty swallowing capsules. If the liquid isn't available, your pharmacist may be able to open capsules and mix the powder with a sweetened liquid — ask your pharmacist for instructions.

Note: The oral suspension contains sorbitol. Patients with hereditary fructose intolerance should use the capsule form instead.

How to Take Tamiflu

For the best results, follow these guidelines:

• Take with food to reduce nausea and stomach upset (the most common side effects of Tamiflu)
• Space doses evenly — about 12 hours apart for treatment (twice daily)
• Complete the full course even if you start feeling better before the 5 days are up
• Start as soon as possible — ideally within 48 hours of symptom onset
• Swallow capsules whole or open and mix with a sweetened liquid if needed
• Shake oral suspension well before each dose

Who Should Take Tamiflu?

Tamiflu can benefit anyone with influenza, but it's especially important for people at high risk of flu complications:

• Adults 65 years and older
• Children under 5, especially those under 2
• Pregnant women
• People with chronic medical conditions (asthma, diabetes, heart disease, immunodeficiency)
• Residents of nursing homes and long-term care facilities
• People with BMI ≥40

Even if you're not in a high-risk group, Tamiflu can reduce the duration of your illness by 1-2 days and help you get back on your feet faster.

Who Should NOT Take Tamiflu?

Tamiflu is contraindicated in patients with:

• Known hypersensitivity to Oseltamivir or any ingredient in the formulation

Additionally:

• Avoid the live attenuated influenza vaccine (LAIV/FluMist) within 2 weeks before or 48 hours after taking Tamiflu
• Use caution in patients with severe kidney impairment — dose adjustments are required
• Tamiflu is Pregnancy Category C — use only if the benefit outweighs the risk, as determined by your doctor

For a full list of interactions, see our guide on Tamiflu drug interactions.

Tamiflu vs. Other Flu Treatments

Tamiflu isn't the only antiviral available for influenza. Here's how it compares to the alternatives:

• Xofluza (Baloxavir Marboxil): A single-dose oral treatment for patients 5 and older. Works by a different mechanism (cap-dependent endonuclease inhibitor). Convenient one-dose regimen but more expensive.
• Relenza (Zanamivir): An inhaled neuraminidase inhibitor. Not suitable for people with respiratory conditions like asthma or COPD.
• Rapivab (Peramivir): An IV neuraminidase inhibitor given as a single infusion. Used in hospital settings or when oral medication isn't possible.

How Much Does Tamiflu Cost?

The cost of Tamiflu varies significantly depending on whether you use brand-name or generic, and whether you have insurance:

• Brand-name Tamiflu: $150-$250 for a 10-capsule treatment course (without insurance)
• Generic Oseltamivir: $25-$135 without insurance; as low as $20-$30 with discount coupons
• With insurance: Typical copay of $0-$75. About 68% of insurance plans cover Tamiflu.

For tips on reducing your out-of-pocket cost, check out our guide on how to save money on Tamiflu.

Finding Tamiflu During the 2026 Shortage

The 2025-2026 flu season has brought intermittent Tamiflu shortages across the country. If you're having trouble finding it:

• Use MedFinder to find pharmacies with Tamiflu in stock
• Ask for generic Oseltamivir — it may be more readily available
• Check pharmacy stock online before heading out

The Bottom Line

Tamiflu remains one of the most effective and widely used antiviral treatments for influenza in 2026. When started within 48 hours of symptoms, it can meaningfully reduce how long you're sick and lower your risk of complications. It's safe for patients as young as 2 weeks old and available in both capsule and liquid form.

If you think you have the flu, see a doctor quickly, get your prescription, and use MedFinder to find a pharmacy that has it in stock. Time is your most valuable resource when it comes to flu treatment.