The standard adult dose of Tamiflu (oseltamivir) is 75 mg taken twice a day for five days. You take one dose in the morning and one in the evening, for a total of ten capsules over the course of treatment. This applies to adults and teenagers 13 and older who are being treated for influenza.
Treatment Dosage and Timing
For flu treatment, you’ll take 75 mg (one capsule or 12.5 mL of the liquid form) every 12 hours for five days. The clock starts when you pick up your prescription, not when your symptoms began, so don’t skip doses to “make up” for lost time.
Timing matters, though. Tamiflu works best when started within 48 hours of your first flu symptoms. The closer to symptom onset you begin, the more effective it is at shortening your illness and reducing severity. Starting on day one is better than day two, and day two is better than day three. After 48 hours, the benefits drop off considerably, though doctors may still prescribe it for high-risk patients regardless of timing.
Prevention Dosage After Exposure
If you’ve been exposed to someone with the flu but aren’t sick yet, the preventive dose is the same 75 mg twice daily, but the duration changes based on your situation. A single, limited exposure (like visiting a sick friend) calls for five days of treatment starting from the last known contact. If you’re living with someone who has the flu and the exposure is ongoing, the recommended course extends to ten days.
During a broader community outbreak, preventive dosing can continue for up to six weeks, though in that case the frequency drops to 75 mg once daily rather than twice.
What to Do If You Miss a Dose
Take the missed dose as soon as you remember, with one exception: if your next scheduled dose is less than two hours away, skip the missed one and resume your normal schedule. Never double up to compensate. If you miss several doses in a row, contact your prescriber for guidance on whether to adjust your remaining course.
Common Side Effects
Nausea and vomiting are the most frequently reported side effects. In clinical trials, about 10% of adults experienced nausea and roughly 9% had vomiting, compared to 6% and 3% in people taking a placebo. That means some of that nausea may actually come from the flu itself rather than the medication. Taking Tamiflu with food can help reduce stomach upset.
These side effects are mild enough that only about 1% of people in trials stopped taking the drug because of them. Rare reports of neuropsychiatric effects like confusion or delirium have surfaced in post-marketing surveillance, primarily among Japanese adolescents and adults, but these events are uncommon.
Dose Adjustments for Kidney Problems
If you have significant kidney impairment, your dose will likely be reduced. Adults with poor kidney function (specifically, a creatinine clearance between 10 and 30 mL/min) take 75 mg once daily instead of twice daily for treatment. For prevention, the dose drops further to 75 mg every other day or 30 mg daily. Your doctor will determine your kidney function through blood tests and adjust accordingly. There is no established dosing for people on dialysis.
Tamiflu and the Flu Vaccine
If you’re taking Tamiflu and need a flu vaccine, the type of vaccine matters. The nasal spray vaccine (the live version) should not be given until at least 48 hours after your last Tamiflu dose, because the drug can neutralize the live virus in the vaccine before your immune system responds to it. Going the other direction, you should wait two weeks after receiving the nasal spray vaccine before starting Tamiflu. Injectable flu vaccines (the inactivated kind) are not affected by Tamiflu and can be given at any time.