Frequently asked questions.

When to take antibiotics (Bacteria vs Virus)

What kind of infections can antibiotics be used to treat?

Antibiotics only work on some bacterial infections. They do not work for viruses.

It can be hard to tell the difference between a bacterial and a viral infection, but most common illnesses like coughs, colds and sore throats are caused by viruses. Viral infections cannot be treated with antibiotics. It is then about managing your symptoms.

You can explore the symptoms and treatments of common infections here.

If you are unsure about your symptoms, or they last longer than they normally should, you can get professional advice from your pharmacist who can also let you know if you should see your doctor.

What’s the difference between bacteria and viruses?

Bacteria are tiny living things that get nutrients from their environment. Most bacteria that live in your body are good. They help digest food, give nutrients and protect you against harmful germs. Sometimes harmful bacteria can get into your body and cause you to feel unwell.

Common infections caused by bacteria are some sore throats and UTIs like cystitis. Some infections caused by bacteria need to be treated with antibiotics.

Viruses are much smaller than bacteria and they are different as, unlike bacteria, most viruses cause illness. A viral infection begins when a virus attacks healthy cells in your body. Once there it takes over, creating more viruses like itself. Illnesses caused by viruses include common colds, chicken pox and coronavirus.

Antibiotics do not work for infections caused by viruses.

How to take antibiotics

How important is it that I finish the course of antibiotics that I’ve been prescribed?

Even if you start to feel better after a few days, it is really important you complete the course of antibiotics exactly as your doctor or other healthcare professional advised.


If you don’t take the full course of antibiotics, there’s a chance that the bacteria is not completely killed off. This means the infection can return, and it might be worse the second time around.

At the same time, the surviving bacteria in your system might be able to learn how to resist and fight back against what is supposed to kill it. If you don’t use the full course of antibiotics to kill off the bacteria completely, the chances are increased that bacteria develops antibiotic resistance.

As bacteria develop antibiotic resistance, infections will become harder to treat. Operations and other treatments will become more dangerous.

Do I need to take antibiotics at certain times of day or always with food?

It is important to follow the instructions on the label or those given to you by your doctor. The main reason antibiotics are taken at a certain time of day, whether with or after food, is so that the medicine is absorbed into the bloodstream correctly.

Taking a dose too soon, missing a dose or waiting too long between doses can prevent the antibiotics working properly.

Some antibiotics need to be taken before food. Some need to be taken with or just after food. The general advice is to space doses evenly throughout the day, follow the instructions for the specific antibiotic you have been prescribed, and keep taking them until the course is finished or you are told to stop.

Storing and sharing antibiotics

Can I save any left over antibiotics for the next time I get ill or someone in my family needs them?

If you take your course of antibiotics as prescribed, there should be none left over. If there are, you can take them back to your local pharmacy, where they will be disposed of properly. Please do not put them in your bin or flush them down the toilet. They should not be used to treat a later illness or shared with family or friends.


Taking antibiotics that have not been prescribed to you for a specific infection can lead to the overuse or misuse of antibiotics. Antibiotics are prescribed to different people for different reasons, even if symptoms might be similar. Using old antibiotics or sharing them could mean delaying effective treatment, make you or your family member sicker and even cause side effects.

Delayed or ineffective treatment can lead to the development of antibiotic resistant bacteria, making treatment in the future more difficult.

Drinking alcohol whilst on antibiotics

Is it okay to drink alcohol while taking antibiotics?

With most antibiotics there’s no reason you can’t drink sensibly and in moderation. But there are a few things to think about if you decide to have a drink.

If you are taking antibiotics because you have an infection, you probably don’t feel well. If you have too much alcohol, it is likely to make you feel more unwell and may make any side effects from the antibiotics worse.

Some specific antibiotics can have a very nasty reaction with alcohol. The most common of these is metronidazole. Mixing alcohol with these antibiotics can lead to flushing, headaches, nausea, vomiting and stomach cramps. Always read the warnings on your medicine label and avoid alcohol if advised to do so.

If you’re not sure, speak to your doctor, dentist or pharmacist about your specific antibiotics and drinking alcohol.

Extra professional support

Who can I go to for help if I'm not sure about my symptoms?

Speak to your pharmacist. They can help you choose the medicine that will work best for you and advise you to see a doctor or other healthcare professional if necessary. They can also provide help and advice for looking after yourself in general through a healthy lifestyle.

People working in pharmacies are highly qualified and experienced when it comes to expert advice on minor illnesses. They can tell you what products are available to help reduce your symptoms. You can get advice over the phone or in person, and many are open late or on the weekend

If you are ever worried that your symptoms might be something more severe, you can visit or call NHS 111.

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