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Antibiotics
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Infections

Antibiotics

Antibiotics are essential tools for fighting bacterial infections, but they must be used responsibly to avoid side effects and the development of antibiotic resistance.

What are antibiotics?

Antibiotics are medicines that fight bacterial infections in people and animals. They work by killing the bacteria or by making it hard for the bacteria to grow and multiply.

Antibiotics can be taken in different ways:

  • Orally (by mouth): This could be pills, capsules, or liquids.
  • Topically: This might be a cream, spray, or ointment that you put on your skin. It could also be eye ointment, eye drops, or ear drops.
  • Through an injection or intravenously (IV): This is usually for more serious infections.

What do antibiotics treat?

Antibiotics only treat certain bacterial infections, such as strep throat, urinary tract infections, and E. coli. You may not need to take antibiotics for some bacterial infections, such as many sinus infections or some ear infections. Taking antibiotics when they're not needed won't help you, and they can have side effects. Your health care provider can decide the best treatment for you when you're sick; do not ask your provider to prescribe an antibiotic for you.

Do antibiotics treat viral infections?

Antibiotics do not work on viral infections. For example, you shouldn't take antibiotics for:

  • Colds and runny noses, even if the mucus is thick, yellow, or green
  • Most sore throats (except strep throat)
  • Flu
  • Most cases of bronchitis

What are the side effects of antibiotics?

The side effects of antibiotics range from minor to very severe. Some of the common side effects include:

  • Rash
  • Nausea
  • Diarrhea
  • Yeast infections

More serious side effects can include:

  • C. diff infections, which cause diarrhea that can lead to severe colon damage and sometimes even death
  • Severe and life-threatening allergic reactions
  • Antibiotic resistance infections

Call your health care provider if you develop any side effects while taking your antibiotic.

Why is it important to take antibiotics only when they're needed?

You should only take antibiotics when they are needed because they can cause side effects and can contribute to antibiotic resistance. Antibiotic resistance happens when the bacteria change and become able to resist the effects of an antibiotic, meaning the bacteria continue to grow.

How do I use antibiotics correctly?

When you take antibiotics, it is important that you take them responsibly:

  • Always follow the directions carefully. Finish your medicine even if you feel better. If you stop taking them too soon, some bacteria may survive and re-infect you.
  • Don't save your antibiotics for later.
  • Don't share your antibiotic with others.
  • Don't take antibiotics prescribed for someone else. This may delay the best treatment for you, make you even sicker, or cause side effects.

Frequently Asked Questions

For most antibiotics, moderate alcohol consumption is not strictly contraindicated, but it can worsen common side effects like nausea, dizziness, and liver stress. However, certain antibiotics, such as metronidazole and tinidazole, cause a severe disulfiram-like reaction when combined with alcohol, leading to vomiting, flushing, and rapid heart rate. You must avoid alcohol completely for at least 48 to 72 hours after finishing these specific medications. Always check the label or consult your pharmacist to confirm if your specific antibiotic interacts with alcohol.
It depends on the specific antibiotic. Some antibiotics, such as tetracyclines and fluoroquinolones, can have their absorption significantly reduced if taken with antacids containing aluminum, magnesium, or calcium, or with iron and zinc supplements. Always check the medication guide or ask your pharmacist about timing. Generally, it is safe to take acetaminophen or ibuprofen for pain or fever, but you should separate the doses from your antibiotic by at least two hours if your provider has not specified otherwise.
If you miss a dose, take it as soon as you remember unless it is almost time for your next scheduled dose. In that case, skip the missed dose and resume your regular schedule. Never double up on doses to make up for a missed one, as this increases the risk of severe side effects. Missing doses can lead to sub-therapeutic drug levels, which may allow bacteria to survive and potentially develop resistance. If you miss multiple doses, contact your healthcare provider for guidance on whether to restart the course or adjust the regimen.
There is no fixed waiting period, but your healthcare provider will determine the appropriate timing based on the type of new infection and your medical history. If you develop a new infection shortly after finishing a course, it is crucial to inform your provider about the previous antibiotic you took. This helps them choose a different class of medication if necessary to avoid cross-resistance or cumulative side effects. Do not self-prescribe leftover antibiotics for a new issue, as this is a major driver of resistance.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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