Can I drink alcohol if I'm taking Tamiflu?

There is nothing in the prescribing information to suggest that it is a problem
http://www.drugs.com/pro/tamiflu.html
but if you are taking Tamiflu for the flu you might help your recovery by taking it easy.

What can be done to prevent or treat the flu?

* Avoid spreading germs: You can decrease your chance of getting lung infections and other illnesses by doing the following:

o Wash your hands often with soap and water. Carry germ-killing hand lotion or gel with you when you leave the house. You can use the lotion or gel to clean your hands when there is no water available.

o Do not touch your eyes, nose, or mouth unless you have washed your hands first.

o Always cover your mouth when you cough. It is best to cough into a tissue or your shirtsleeve, rather than into your hand. People around you should also cover their mouths when they cough.

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o Try to avoid people who have a cold or the flu. If you are sick, stay away from others as much as possible.

* Influenza vaccine: Receiving an influenza vaccine each year helps to decrease your chances of getting the flu. The best time to get the influenza vaccine is in October or November. Ask your caregiver which type of influenza vaccine is right for you.

* Antiviral medicine: Antiviral medicine may help decrease the number of days you are sick. This medicine works only if you take it within one to two days of the start of your symptoms.

* Other treatments for flu symptoms: Rest and drink at least eight to ten (8 ounce) cups of liquids each day. Do not drink alcohol or use tobacco. Use a cool mist humidifier to help you breathe easier. Take acetaminophen or ibuprofen for body aches and fever. Do not take aspirin. Ask your caregiver to help you choose the right medicine for you if you have a cough.

from http://www.drugs.com/cg/influenza.html