Oseltamivir (Tamiflu) Capsules: Uses, Dosage & Side Effects

02/10/2026

What are Oseltamivir (Tamiflu) Capsules intended for?

Tamiflu contains Oseltamivir as its primary active ingredient, which is placed under the drug class known as influenza antivirals. This medication is primarily prescribed to treat flu, including influenza A and B. However, it needs to be taken within the first 2 days of experiencing flu symptoms. Additionally, it is also prescribed for the prevention of the flu in teenagers and adults. The flu, also known as influenza, is an infection of the nose, throat, & lungs, with common symptoms including sore throat, body aches, fatigue, and fever.

This medication is a neuraminidase inhibitor. This medication works by inhibiting neuraminidase, which allows the virus to enter uninfected cells and spread the infection throughout the body, allowing your body to fight off the infection. 

Dosing of Oseltamivir (Tamiflu)

The dosage of Oseltamivir (Tamiflu) usually varies from one person to another for a variety of reasons and depends on factors such as age, weight, severity of the disorder, etc. Therefore, it is imperative to see a doctor to find the correct dosage.  You should always abide by the dosage advised by the doctor for maximum results and don’t deviate from it unless advised to do so. If you change the prescribed dosage on your own, you increase the risk of repercussions.

The amount of medicine you need to take in a day depends on the strength and number of doses you are taking. The dosing mentioned below is general and should be taken into consideration after consulting a healthcare provider. The dosage may change, reduce, or increase, depending on your individual case. 

For the management of the flu (Capsules and suspension):

Adults: The correct dosage will be decided by your medical professional and typically depends on the severity of the disorder.  The typical dose for adults is 26 mg or 12.5  mL once in the morning and once in the evening for 5 days. 

Children aged 1 year and older: The dose will be determined by your medical professional based on your body weight and other factors. The usual dosage for this age group is 30 to 75 mg or 5 to 12 mL twice a day for 5 days or as advised by the doctor.

Children under 1 year old or 2 weeks old: The dose will depend on body weight and be determined by your healthcare provider. The typical dose for this age group is 3 mg per kg twice a day for 5 days.

For the prevention of the flu:

Adults and teenagers: The typical dosage is 75 mg or 12.5 mL once a day for around 10 days.

Children aged 1 year and older: The typical dosage is 30 to 75 mg or 12.5 mL once a day for approximately 10 days. 

Children younger than 1 year: This medication is not recommended for children younger than 1 year. 

Side effects of Oseltamivir (Tamiflu) Capsules 

Based on severity, Tamiflu side effects are classified into two categories: common and serious. Common side effects of this medication are mild and usually occur during the first few days of treatment. As soon as the body acclimates to the medication, common side effects start to wear off. However, if they become bothersome or continue to persist, kindly seek medical attention at the earliest. The Oseltamivir’s common side effects are as follows: 

• Nausea

• Vomiting

• Headache

• Pain 

Serious side effects of this medication are more likely to occur in people who are beginning the treatment with a higher strength. While they occur in rare instances, you are required to report to the doctor as soon as possible if you come across any of them.  The following are the serious side effects of this medication:

Allergic reaction:

The use of oseltamivir phosphate can induce serious allergic reactions, which can be life-endangering if not addressed in a timely manner. If you develop any symptoms of allergic reaction due to the consumption of the medication, please seek immediate medical attention to prevent additional complications. The following are the symptoms of an allergic reaction:

• Breathing problems or wheezing

• Racing heart

• Fever or general ill feeling

• Swollen lymph nodes

• Nausea or vomiting

• Dizziness, feeling lightheaded, or fainting

• Stomach cramps

• Swelling in the face, tongue, lips, mouth, or throat

• Trouble swallowing or throat tightness

• Itching, skin rash, or pale red bumps on the skin are called hives 

Severe skin reaction:

Although rare, the use of this medication can result in serious skin reactions, for instance, toxic epidermal necrolysis, Stevens-Johnson syndrome, or erythema multiforme. These skin reactions can even cause death if left untreated. If you come across any symptoms of skin reaction, get medical help instantly:

• Painful red or purple skin that appears to be burned and peels off

• Flat red rash/blisters on your skin, nose, mouth & genitals

• Red, watery, painful eyes

• Flat, round red patches that have dark circles with purple-grey centers

• Red patches or blisters on the palms of hands, face, and soles of feet 

Warnings and precautions to be exercised while using oseltamivir phosphate 

Before you start taking this medication, make sure to read the precautions and warnings. These preventive measures will help you get the maximum result while minimizing the possibility of stumbling upon unwanted complications. If you have any concerns related to the guidelines mentioned below, please talk to your doctor or pharmacist.

Allergic to ingredients:

If you have a known allergy to active or inactive ingredients of this medication, please let your doctor know beforehand. If taken into use despite being aware of this, it may induce a wide range of complications, ranging from serious allergic reactions to severe side effects. To get the full list of ingredients for the specific oseltamivir you have been prescribed, please ask your pharmacist.

Current and past medical history:

If you have or have had any serious medical condition, especially those affecting vital organs, please let your doctor know beforehand. This will help your doctor determine the associated risks and benefits of this medication for you. In addition to this, you should also share the list of all medications you are currently taking, including prescription, over-the-counter, and herbal products. Other medications can interact with this medication, reducing the efficacy of oseltamivir and increasing the chance of side effects. An interaction between two drugs can sometimes lead to severe complications.

Fructose intolerance:

This medication should be given cautiously to people with hereditary fructose intolerance. One 75 mg dose of Oseltamivir oral liquid carries approximately 2 grams of sorbitol. This amount of sorbitol is not considered safe for people with hereditary fructose intolerance, increasing the chance of upset stomach and diarrhea.

Pregnancy and nursing:

The safety of this medication has not been established in pregnant and lactating women. Therefore, you are requested to consult your doctor before taking this medication. The doctor will examine the associated benefits and risks. You will be prescribed this medication only when the benefits outweigh the risks. In addition, this drug can pass into the infant via breast milk, increasing the risk of side effects. The doctor may prescribe an alternative treatment that aligns with your health goals. 

The takeaway: 

Oseltamivir (Tamiflu) is nothing less than a breakthrough in medical science, allowing us to treat and prevent the flu, which accounts for millions of cases every year. The flu is a common respiratory illness that you get from the influenza virus, causing a wide range of irksome symptoms. This medical condition is more common in the winter, peaking between December and January. If not managed early, it can lead to serious complications. However, treating and preventing is easier than ever, all thanks to medical advances like Oseltamivir (Tamiflu). This medication can help you tackle this condition easily only if you follow the prescribed dosage and other preventive measures. Make sure not to deviate from the prescribed path, or your risk of side effects increases.