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What happens if I take antibiotics without an infection?

Antibiotics are medications used to treat bacterial infections. They work by killing bacteria or preventing them from multiplying. Antibiotics are one of the most commonly prescribed medications, especially for conditions like sinus infections, strep throat, and urinary tract infections. But what happens if you take antibiotics when you don’t actually have an infection? Let’s take a closer look.

Can I take antibiotics as a precaution?

Some people think taking antibiotics as a precaution, before any signs or symptoms of infection, is a good idea. However, this practice is not recommended and can do more harm than good. Here’s why:

  • Antibiotics won’t prevent infections – Antibiotics only work on bacterial infections. They have no effect on viruses. So taking antibiotics when you don’t have any symptoms of infection is unlikely to prevent you from getting sick.
  • Overuse promotes antibiotic resistance – Bacteria can become resistant to antibiotics when they are overused. If you take antibiotics when you don’t need them, bacteria in your body can become resistant. This makes antibiotics less effective against infections.
  • May cause side effects – Like any medication, antibiotics can cause side effects like diarrhea, nausea, vomiting, and allergic reactions. It doesn’t make sense to take this risk if you don’t have an infection.

Instead of taking antibiotics as a precaution, a better approach is practicing good hygiene and getting recommended vaccines to prevent infections from developing in the first place.

What if I stop taking antibiotics too soon?

It’s very important to take antibiotics exactly as prescribed and complete the full course. Stopping antibiotic treatment too soon can allow the toughest bacteria to survive. Here’s what happens:

  • Bacteria may only be weakened, not killed – Shortened antibiotic courses don’t always kill all the bacteria causing an infection. The strongest bacteria can survive and multiply.
  • Increased risk of antibiotic resistance – Surviving bacteria are more likely to become resistant to the antibiotics taken.
  • Infection returns – Since all bacteria weren’t killed, stopping antibiotics too soon often leads to the infection returning and worsening.
  • Need for more aggressive treatment – To treat the returned infection, longer or more powerful antibiotic regimens may be needed.

Make sure to work with your doctor and follow instructions closely when taking prescribed antibiotics. Never stop antibiotics early without your doctor’s approval.

What are the risks of taking antibiotics unnecessarily?

Here are some of the main risks associated with taking antibiotics when you don’t have a bacterial infection that requires them:

  • Antibiotic resistance – As mentioned, antibiotic overuse promotes the development of resistant bacteria. These “superbugs” can cause infections that are very difficult to treat.
  • Medication reactions – Up to 10% of people using antibiotics experience side effects like rash, dizziness, nausea, diarrhea, and yeast infections. You’re needlessly putting yourself at risk if you don’t have an infection.
  • Infection with resistant organisms – Being on antibiotics raises your risk of getting sick from bacteria that are resistant to the antibiotics you’re taking, like C. difficile.
  • Altered microbiome – Antibiotics kill good gut bacteria along with the bad. This can allow overgrowth of harmful bacteria and cause digestive issues.
  • Interactions with other medications – Antibiotics can interact with many medications, including birth control pills, blood thinners, and certain antidepressants.

Overall, you upset the balance of microorganisms in your body when antibiotics are used unnecessarily. This puts you at risk for both immediate side effects and long-term health consequences.

What about using leftover antibiotics?

It’s common for patients to have antibiotics left over after finishing a course. But it’s important not to take these leftover antibiotics for the following reasons:

  • Your current illness may be viral – Viral infections won’t respond to leftover antibiotics prescribed for a previous bacterial infection.
  • Bacteria change over time – The bacteria behind your current illness may be different or resistant to your leftover antibiotics.
  • The dosing may be incorrect – You might have the wrong dose or duration to effectively treat your new illness.
  • The antibiotics may have expired – Antibiotics expire and can become less potent or even toxic over time.

Instead of reaching for leftover antibiotics, it’s best to be evaluated by your doctor to determine if antibiotics are needed and get a tailored prescription. Never prescribe antibiotics for yourself or others using old prescriptions.

When are antibiotics necessary?

Antibiotics are lifesaving medications when used properly for bacterial infections. Here are examples of appropriate uses for antibiotics based on evidence of a likely bacterial infection:

  • Positive lab test confirming a bacterial infection, like a positive throat culture for strep bacteria.
  • High suspicion of bacterial infection based on symptoms, like a persistent cough with thick green mucus pointing to a possible bacterial pneumonia.
  • Known risk factors for bacterial infections, like a urinary tract infection (UTI) in someone with a urinary catheter.
  • Severe infection requiring prompt treatment before lab results return, like sepsis.

However, antibiotics are often overused and prescribed inappropriately. It’s estimated that 30-50% of antibiotics prescribed in hospitals are unnecessary or inappropriate. To combat antibiotic overuse, doctors are encouraged to only prescribe antibiotics when evidence clearly indicates they are needed.

What should I do if symptoms persist after taking a full course of antibiotics?

It can be concerning if symptoms of an infection persist after completing a course of antibiotics. Here are some steps to take:

  • See your doctor – Follow up and get reevaluated, as you may require a different antibiotic or longer treatment course.
  • Consider other causes – Persistent symptoms may be from something other than bacteria, like a virus or underlying condition.
  • Get a culture done – Lab tests can identify the specific bacteria causing illness and its antibiotic resistance.
  • Look for complications – Severe infections may create complications like abscesses that require drainage or surgery along with antibiotics.
  • Watch for recurrence – Some treated infections can recur after antibiotic treatment stops. Monitor symptoms closely.

Don’t self-prescribe another course of antibiotics. Work with your doctor to establish why symptoms are not resolving and develop an appropriate treatment plan. Prompt medical care is key for severe infections not responding to initial antibiotic treatment.


Antibiotics can do tremendous harm when used inappropriately. Take antibiotics only when prescribed for diagnosed bacterial infections. Complete the full antibiotic course and never save leftovers or share prescriptions. Seek medical evaluation if symptoms persist after antibiotic treatment. Taking antibiotics responsibility is crucial to your health and that of the community.