Antibiotics: When You Need Them and When You Don't

What antibiotics do and how they work

Antibiotics are designed to kill bacteria or stop them from multiplying. They are used for infections caused by bacteria, such as some ear infections, strep throat, certain skin infections, urinary tract infections, and some respiratory infections. When used appropriately, they can shorten illness, reduce complications, and help you recover.

Different antibiotics work in different ways and are chosen based on the likely bacteria, the infection site, local resistance patterns, allergies, age, pregnancy status, and other health factors. Two commonly prescribed antibiotics in the U.S. are amoxicillin and azithromycin. Amoxicillin is a penicillin-type antibiotic often used for ear, sinus, throat, and some dental infections, while azithromycin is used for certain respiratory, skin, and sexually transmitted infections, among others.

• Antibiotics treat bacterial infections, not viral ones.
• The right antibiotic depends on the type of infection and your medical history.
• Taking the wrong antibiotic may not help and can cause harm.

When you do need antibiotics

Antibiotics are appropriate when a healthcare professional suspects or confirms a bacterial infection. Examples include strep throat, some cases of pneumonia, bladder infections, infected wounds, and certain sinus or ear infections that do not improve on their own. In these situations, timely treatment may prevent the infection from getting worse.

Your clinician may diagnose a bacterial infection by examining you, reviewing your symptoms, and sometimes ordering tests. For example, a rapid strep test or throat culture can help determine whether sore throat is caused by strep bacteria. A urine test may help confirm a urinary tract infection. If your provider prescribes amoxicillin or azithromycin, it is important to take it exactly as directed and complete the full course unless your clinician tells you otherwise.

• Strep throat
• Some pneumonias
• Certain ear, sinus, skin, and urinary tract infections
• Some dental infections

When antibiotics do not help

Antibiotics do not treat viral infections. That means they will not work for the common cold, flu, most cases of bronchitis, COVID-19, or many sore throats and sinus infections. Using antibiotics for these illnesses will not make symptoms improve faster and can expose you to unnecessary side effects.

A frequent reason people ask for antibiotics is because symptoms are severe, but severity alone does not prove bacteria are the cause. A high fever, cough, congestion, or colored mucus can happen with viral infections too. The best approach is to get evaluated if symptoms are prolonged, severe, or worsening, rather than assuming an antibiotic is needed.

• Common cold
• Flu
• Most viral bronchitis
• Most sore throats and sinus infections

Why unnecessary antibiotic use is a problem

Taking antibiotics when they are not needed can cause side effects such as nausea, diarrhea, rash, yeast infections, and, in some cases, allergic reactions. More seriously, antibiotic use can disturb normal bacteria in the body and raise the risk of infections like Clostridioides difficile, which can cause significant diarrhea and colon inflammation.

Overuse also contributes to antibiotic resistance. This happens when bacteria change in ways that make antibiotics less effective. Resistant infections can be harder to treat, may require stronger medicines, and can lead to longer illness or hospitalization. Using antibiotics only when truly needed helps preserve their effectiveness for everyone.

• Side effects may include diarrhea, nausea, rash, and allergic reactions.
• Antibiotic resistance can make future infections harder to treat.
• Unneeded antibiotics can disrupt healthy bacteria.

What to know about amoxicillin and azithromycin

Amoxicillin and azithromycin are widely used prescription antibiotics, but they are not interchangeable. Amoxicillin is commonly used for infections caused by bacteria that are sensitive to penicillin-type drugs. It may be a first-choice option for some ear, throat, sinus, and dental infections, depending on the case.

Azithromycin is often chosen for certain respiratory infections and some sexually transmitted infections, but it is not the best option for every bacterial infection. It can interact with other medicines and may not be appropriate for people with certain heart rhythm problems. If you are prescribed either medicine, tell your clinician about allergies, pregnancy, liver issues, heart conditions, and all medications and supplements you take.

• Amoxicillin is a penicillin-type antibiotic.
• Azithromycin is used for select bacterial infections.
• Do not share antibiotics or use leftover pills.

How to use antibiotics safely

If you are prescribed an antibiotic, follow the directions exactly. Take it at the scheduled times, with or without food as instructed, and finish the course unless your prescriber tells you to stop. Missing doses or stopping early can make treatment less effective and may allow bacteria to survive.

Call a healthcare professional if you develop a rash, trouble breathing, severe diarrhea, or signs your infection is getting worse. Also ask before taking antacids, supplements, or over-the-counter medicines if you are on a prescription antibiotic, because some products can affect how well treatment works. If your symptoms do not improve as expected, follow up rather than self-treating with another antibiotic.

• Take exactly as prescribed.
• Do not save antibiotics for later use.
• Seek medical advice for side effects or worsening symptoms.

Common questions