Using antibiotics unnecessarily or excessively is known as antibiotic overuse. Some effects of overuse can include an increased risk of antibiotic-resistant infections and other antibiotic-related complications.

Overuse of antibiotics is both an individual and public health problem. Individuals who overuse antibiotics may be more vulnerable to antibiotic-related complications such as digestive problems, yeast infections, and allergic reactions.

From a public health perspective, widespread antibiotic overuse allows bacteria to evolve resistance to antibiotics rapidly. This can create infections that do not respond to typical treatments. Many public health agencies have published guidelines to help prevent antibiotic overuse.

Read on to learn more about the effects of overusing antibiotics.

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Antibiotic overuse is when a person uses antibiotics too often or for the wrong reasons. Some examples of overuse include:

  • taking leftover antibiotics or someone else’s antibiotics
  • pressuring a doctor to prescribe antibiotics when they say it is unnecessary to do so
  • taking the wrong dose of antibiotics, such as by taking them irregularly or stopping taking them too soon
  • taking too many antibiotics, such as when a doctor prescribes an excessively high dose or IV antibiotics when they are not necessary
  • taking antibiotics for a virus or other nonbacterial infection

Antibiotics can clear infections quickly, reduce pain, and even save a person’s life. However, using antibiotics a person does not need will not improve their health or make them feel better. In fact, they cause experience avoidable side effects.

Below are details about what can occur as a result of antibiotic overuse.

Antibiotic resistance

Bacteria, as with all organisms, evolve in response to environmental pressures. Some bacteria possess mutations that allow them to resist antibiotics and gain an advantage. Typically, when only a few bacteria have natural resistance, the body can fight them off. But as more bacteria become resistant, an infection can overwhelm the body.

When there is widespread antibiotic use, resistant bacteria become more common. This can cause antibiotic resistance.

Antibiotic-resistant bacteria can be very dangerous. A person might need to take several antibiotics before one works. And an untreated infection can lead to serious health outcomes and even death.

Learn more about antibiotic resistance.

Antibiotic side effects

No drug is without risk or side effects. Every drug a person uses increases their risk of experiencing side effects. Antibiotics can cause various side effects, depending on individual circumstances and the specific drug. These can include:

People can also have dangerous, sometimes life threatening allergic reactions to antibiotics.

Taking antibiotics is also a risk factor for developing a Clostridioides difficile (C. diff) infection. C. diff is a bacteria that can cause serious digestive issues such as colon inflammation. People with weakened immune systems may be at increased risk.

Learn more about the side effects of antibiotics.

Drug interactions

Antibiotics can interact harmfully with some other drugs. The more medications a person takes, the more likely those medications are to interact. A doctor can advise on possible interactions a person’s medications may cause.

Drug interactions are especially likely when a person takes antibiotics outside of the supervision and guidance of a doctor.

Learn more about drug interactions.


Antibiotics increase healthcare costs. When antibiotics are unnecessary or harmful, they may increase costs even more by causing harmful interactions or side effects that may require additional doctor visits or even hospitalization.

Microbiome disruption

The microbiome is a collection of good and potentially harmful bacteria in a particular environment. Antibiotics tend to affect the microbiome of the gastrointestinal tract or, more specifically, the gut. Broad-spectrum antibiotics can kill various bacteria, including beneficial bacteria in the gut.

Researchers are still studying the microbiome to understand how beneficial bacteria affect health. These bacteria likely play a role in many aspects of health, including digestion.

Some people also experience nonbacterial infections, such as yeast infections, after taking antibiotics.

Overusing antibiotics affects the microbiome, killing some beneficial bacteria in the body when doing so is unnecessary.

Learn more about the human microbiome.

Antibiotics in the environment

Antibiotic overuse can potentially mean that there are also more antibiotics in the environment, for example, in landfills, in the water supply, and in animals that people eat for food. This can generate additional antibiotic resistance.

Also, antibiotics in the environment can harm plants and animals, kill beneficial bacteria, and cause other environmental damage.

Antibiotic stewardship refers to the practice of using antibiotics wisely and only when necessary.

It requires healthcare professionals and people who are unwell to work together. Doctors and other prescribers should:

  • only prescribe antibiotics when there is clear evidence of infection
  • give clear instructions about how to use antibiotics and the risks of misuse
  • get a medical history and ask about other drugs
  • ask about past and current antibiotic use

People seeking medical care should:

  • give clear and specific details about their symptoms and medical history
  • not take another person’s antibiotics
  • not take old antibiotics
  • take the entire course of antibiotics, even if symptoms resolve
  • take antibiotics exactly as prescribed to them
  • practice infection prevention strategies, such as handwashing and masking, to reduce their risk of infection and their need for antibiotics

Antibiotic overuse can damage an individual’s health, causing immediate complications such as side effects and drug interactions. It is also a public health threat that can increase antibiotic resistance, leading to resistant bacterial infections.

People with infections should seek medical care if they think it might be bacterial. A doctor can best advise on the right course of treatment.

Safe disposal of medication

Inappropriately discarded drugs can harm people, animals, and the environment. It is essential to dispose of any unwanted medication safely. Read our guide on medication disposal here.

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