December 9, 2022

Side effects of antibiotics


Healthcare professionals prescribe antibiotics to prevent and treat bacterial infections. Most of the side effects associated with antibiotics are not life threatening. However, antibiotics can cause serious side effects in some people who require medical attention.

Antibiotics are generally safe and doctors prescribe them to stop the growth of bacteria; for example, to treat bacterial infections, such as strep throat, urinary tract infections (UTIs), and some skin infections.

Antibiotics don’t work against viruses that cause most upper respiratory infections, the common cold, or COVID-19.

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However, antibiotics can cause side effects, ranging from minor to severe, and even fatal. According to the Centers for Disease Control and Prevention (CDC), 1 of 5 medication-related emergency room visits are due to side effects of antibiotics.

Anyone with a serious antibiotic side effect should consult a healthcare practitioner. A person with symptoms of anaphylaxis, such as difficulty breathing, chest pain, or a tightness in the throat, should call 911.

This article explores the common and rare side effects of antibiotics, including long-term side effects and when to see a doctor.

Learn more about bacteria here.

Whenever a person takes an antibiotic, they may experience some common side effects, such as:

Digestive issues

Digestive symptoms can include:

Sometimes a person has to take antibiotics with food; other times, they must be taken on an empty stomach. A person can talk to their doctor or pharmacist about the best way to take their antibiotic.

Most digestive problems go away once a person stops taking the antibiotic.

People with digestive side effects, such as bloody diarrhea, severe abdominal pain, or uncontrollable vomiting, should stop taking their antibiotics and contact a doctor immediately.

Learn more about other common digestive disorders here.

Fungal infection

Antibiotics are drugs that kill harmful bacteria. However, they sometimes kill the good bacteria that protect people from fungal infections and upset the natural balance of the body’s natural flora.

Due to this imbalance, taking antibiotics can lead to fungus (candida) infection of the mouth, digestive tract or vagina.

Candidiasis in the mouth and throat is also called thrush.

Symptoms of thrush can include:

  • white spots on the throat, cheeks, palate, or tongue
  • pain when eating or swallowing
  • bleeding when brushing teeth

Doctors usually prescribe antifungal drugs such as nystatin to treat fungal infections.

Learn more about the gut microbiota here.

Antibiotics UTI and yeast infections

Treating a UTI with antibiotics can sometimes lead to a vaginal yeast infection.

Symptoms of a vaginal yeast infection can include:

Doctors often prescribe the antifungal drug fluconazole to treat yeast infections caused by UTI antibiotics.

Learn more about safe sex and a urinary tract infection.

Drugs interactions

Some can interact with a person’s other medications or supplements.

Symptoms of drug interactions range from mild to life-threatening. Some common warning signs after taking the medicine include:

  • to be nauseous
  • feeling very tired or very energetic

According to Food and Drug Administration (FDA)drug interactions may make an antibiotic less effective or increase the action of a particular drug.

It is generally a good idea to avoid alcohol while taking antibiotics. Drinking alcohol while taking certain antibiotics may decrease the effectiveness and increase the risk of side effects from antibiotics.

Antibiotics that may interact with alcohol include:

To avoid drug interactions with antibiotics, people should always review newly prescribed medications with their doctor or pharmacist. Patient education inserts also list any medications that may interact with the prescribed antibiotic.

Learn more about alcohol and antibiotics here.


Some medications, including antibiotics, make the skin more sensitive to the sun. This is a condition called photosensitivity.

Symptoms of photosensitivity include:

  • skin discoloration, similar to the effects of sunburn
  • inflammation
  • itch
  • blisters that look like hives
  • dry patches

Some antibiotics that can cause photosensitivity include ciprofloxacin, doxycycline, and levofloxacin.

When taking antibiotics that can cause photosensitivity, people should:

  • avoid prolonged periods of exposure to light, especially between hours of 10h00-16h00
  • use a large sunscreen with an SPF value of 15 or higher outdoors, even on a cloudy day
  • wear protective clothing such as wide-brimmed hats, long-sleeved shirts, pants, and sunglasses to limit sun exposure

Anyone who experiences extreme sensitivity to the sun while taking antibiotics should see a doctor.

Learn more about sunburn on dark skin here.


To research suggests that people who take tetracycline develop spots on the skin, nails, teeth and bones. Doctors consider this to be a known but rare side effect of prolonged use of tetracycline.

Teeth staining is irreversible in adults because their teeth do not grow back or change. However, as the bones are continuously reshaping, it is possible to reverse the staining.

A person should discuss switching medications with a doctor if taking antibiotics causes discoloration or staining of the teeth.

Learn more about stained teeth here.

Some of the more serious side effects associated with antibiotics include:


In rare cases, antibiotics can cause an extremely serious allergic reaction called anaphylaxis.

Signs of anaphylaxis include:

Anaphylaxis can be fatal without immediate emergency care. If people suspect anaphylaxis, they should call emergency services or go to the emergency room immediately.

Learn more about the symptoms of anaphylactic shock here.

Clostridium difficile-induced colitis

It’s hard is a type of bacteria that can infect the large intestine and cause It’s hard– induced colitis, which causes inflammation of the intestines and severe diarrhea.

Doctors find It’s hard– induced colitis which is difficult to treat because the bacteria are resistant to most of the available antibiotics.

Severe, chronic or untreated cases of It’s hard-induced colitis can lead to death.

Anyone who is worried about developing an antimicrobial resistant infection while taking antibiotics should talk to a doctor.

Learn more about antimicrobial resistance here.

Antibiotic resistance

Antibiotic resistance occurs when germs develop the ability to overcome the antibiotic’s ability to kill them. This means that the germs keep growing.

Some infections caused by a strain of bacteria resistant to antibiotics do not respond to any available antibiotics. Antibacterial-resistant infections can be serious and potentially fatal.

According to Centers for Disease Control and Prevention (CDC)), at least 2.8 million people in the United States contract antibiotic-resistant bacteria or fungi each year, and more than 35,000 people die from them.

There are some ways to reduce the risk of developing resistance to antibiotics, including:

  • help prevent the spread of infections by getting the right vaccines, washing your hands properly, and staying home when sick
  • follow safe food preparation steps
  • take antibiotics exactly as prescribed by your doctor if you need them
  • discuss with your doctor or pharmacist how to make you feel better if the infection does not require antibiotics
  • never take antibiotics that a doctor has prescribed for someone else
  • never use leftover antibiotics or save extra antibiotics
  • return unused antibiotics to a pharmacy or throw them in the trash

Learn how to safely dispose of medications here.

Kidney disease

According to the National Kidney Foundation, the kidneys eliminate many antibiotic drugs.

When the kidneys are not working properly, these drugs can build up and further damage the kidneys.

Doctors often check blood tests for kidney function before prescribing antibiotics for people with kidney disease.

Learn more about kidney failure here.

According to a to studylong-term side effects of antibiotics in adult women are linked to changes in the gut microbiota. This change is linked to the risks of various chronic diseases, such as cardiovascular disease and certain types of cancer.

This study also indicates that the length of exposure to antibiotics may be a risk factor for premature death.

Additional research has also found that prolonged exposure to antibiotics is associated with an increased risk of gastrointestinal problems in premature babies, late-onset sepsis, or death in very low birth weight infants.

Learn more about sepsis in babies here.

A doctor will usually confirm if a person has a sensitivity or allergy to a particular antibiotic and will likely prescribe an alternative.

If a doctor prescribes an antibiotic, but symptoms persist after a few days of taking it, a person should also see a doctor.

However, anyone who has a serious side effect or allergic reaction when taking antibiotics should immediately stop taking the medicine and see a doctor.

Antibiotics are prescription drugs that kill or prevent the growth of bacteria. Doctors prescribe antibiotics to treat bacterial infections, such as strep throat or skin infections.

Antibiotics usually produce side effects ranging from mild to severe, so a person should only take them when a doctor considers them necessary.

People should report any side effects of antibiotics to their doctor or health care professional.