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When Do You Need an Antibiotic?
These life-saving medications can be helpful, but only when you actually need them
6-minute read
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Key takeaways
- Antibiotics treat bacterial infections, but not viral illnesses such as colds, flu, COVID-19 or RSV.
- Taking antibiotics when they are not needed can increase antibiotic resistance and raise the risk of difficult infections, especially in older adults.
- Ask questions if your doctor prescribes an antibiotic, or if they don’t recommend it.
Battling a fever, stuffy head or chest cold and can’t seem to kick it? You may be tempted to ask your doctor for an antibiotic. But it’s important to know that these medicines only work for certain types of infections — and taking them when you don’t need them could do more harm than good, especially as you age.
Here’s what you need to know about antibiotics, including the questions to ask your doctor if you are prescribed one.
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Antibiotics treat bacterial infections
Many common illnesses that are passed around during the fall and winter — including flu, COVID and RSV — are caused by viral infections. But antibiotics don’t work against viruses; they only treat bacterial infections, says Dr. Preeti Malani, a professor of medicine in the Division of Infectious Diseases at the University of Michigan School of Public Health.
The challenge is that symptoms alone don’t always tell doctors whether an illness is viral or bacterial. A sore throat can be caused by either; so can a cough that won’t let up. That’s why your doctor might run a few tests.
Testing for bacterial infections: Some outpatient tests, such as most strep tests, can identify specific bacteria and help determine whether you need an antibiotic. In other scenarios, your doctor may look for signs of a bacterial infection — or try to rule one out — using blood or sputum samples, or imaging tests.
If the results point to a bacterial infection, your doctor may prescribe an antibiotic based on the bacteria they think are most likely causing your illness. This is known as empiric treatment, and most people get better from it, Malani says. In a hospital setting, doctors may be more likely to order tests to identify the specific bacteria causing your infection.
If you don’t improve on an antibiotic, one possibility is that the bacteria causing your infection are resistant to that medicine. In that case, your doctor may switch you to a different antibiotic. “That’s where some of the diagnostic uncertainty comes in,” says Barbara Santevecchi, a clinical associate professor at the University of Florida College of Pharmacy.
Testing for a viral infection: If you come into the office sick, your doctor may also swab your nose or throat to test for the flu, COVID-19 and other viral illnesses. If the test comes back positive, they’ll know you don’t need an antibiotic, and instead might prescribe an antiviral medication to help you feel better.
A single test that can determine if an illness is viral or bacterial is not yet widely available or routinely used in clinical practice, though that could change in the future.
Older adults are at higher risk for antibiotic-resistant infections
At least 28 percent of antibiotics prescribed in outpatient settings are unnecessary, and about 30 percent prescribed in U.S. hospitals are either unnecessary or suboptimal, the Centers for Disease Control and Prevention (CDC) reports.
Taking an antibiotic when you don’t have a bacterial infection can harm your health. It increases the risk of antibiotic resistance, which occurs when bacteria in your body adapt to the antibiotics, rendering the medicine ineffective in the future. This can make certain bacterial infections more difficult to treat. Not using antibiotics properly can also damage your gut health, since antibiotics can destroy beneficial bacteria in the microbiome.
Each year, 2.8 million Americans acquire antibiotic-resistant infections, according to the CDC, and older adults are disproportionately affected due to several factors, including age-related changes in the immune system and a greater likelihood of having multiple health conditions.
Stays in hospitals and nursing homes can also increase a person’s risk for an antibiotic-resistant infection, or even a multidrug-resistant organism (MDRO) — a germ that resists multiple antibiotics.
About 40 percent of deaths from antibiotic-resistant infections happen in those 65 and older, according to a 2022 study published in Clinical Infectious Diseases.
While most 50-plus adults know overusing antibiotics is problematic because it can lead to antibiotic resistance, results from a 2021 survey published in Infection Control and Hospital Epidemiology found that 34 percent of respondents ages 50 to 80 thought that antibiotics could treat a cold or the flu — viral illnesses that don’t respond to antibiotics. Roughly 40 percent said they’d expect to receive an antibiotic if they went to the doctor for a cold or flu.
Older adults are more likely to be prescribed antibiotics
Despite the increased risk of antibiotic-resistant infections, older adults are 1.5 times more likely to receive antibiotics in a given year than younger adults. One study found that adults 65 and older received unnecessary antibiotics at more than 46 percent of visits for respiratory tract infections that were not caused by bacteria.
Part of the reason is that infections can be more dangerous in older adults; they face a higher risk of hospitalization and death, even from common bugs. And because of this higher risk, research has found that doctors may be more inclined to prescribe an antibiotic if they think it will help keep a patient from getting worse, even if it’s not clear whether bacteria are the cause.
Diagnosis can also be complicated because some symptoms in older adults can have many possible explanations. A change in urine odor or color, for example, may raise concern about a urinary tract infection, even though it can also be caused by dehydration, medication, or liver or kidney issues.
If your doctor is considering an antibiotic, be sure to tell them about all the medications and supplements you take, since antibiotics can interact with other drugs, such as blood thinners like warfarin, Malani points out.
Also, tell your doctor if you have a penicillin allergy. It’s possible you’ve outgrown it, since the body usually sheds the allergy antibodies over time. In fact, about 10 percent of people think they have a penicillin allergy, but less than 1 percent actually do, Santevecchi says, citing CDC data.
Common respiratory illnesses won’t respond to antibiotics
What illnesses are treated with antibiotics? They can be effective if you have:
- Strep throat
- Whooping cough
- Urinary tract infection (UTI)
- Bacterial pneumonia
- Syphilis
- Chlamydia
- Gonorrhea
- Some skin infections, like cellulitis
- Some ear infections
Antibiotics won’t work on viral or fungal infections, so they can’t help if you have:
- A cold
- Influenza (flu)
- COVID-19
- Respiratory syncytial virus (RSV)
- Pneumonia from viral or fungal causes
- Viral bronchitis
That said, some viral infections can lead to secondary infections that may be caused by bacteria. In this case, an antibiotic can help clear up the secondary infection.
What to expect on an antibiotic
If you’re prescribed an antibiotic, ask your doctor or pharmacist when to take it and whether it should be taken with food or alongside other medications. You should also ask about any potential side effects or medication interactions, Malani says.
Some antibiotics can cause rash, diarrhea, nausea, dizziness and yeast infections. Serious side effects include severe allergic reactions, severe skin reactions or antibiotic-resistant infections.
“There are no medications that don’t have [possible] side effects,” Santevecchi says.
If your doctor prescribes you antibiotics, you’ll probably be on them for a week or so. Importantly, take them as prescribed, experts stress. You want to make sure they destroy all of the bacteria so it can’t multiply again, even if you feel better after just a few days. Ask your doctor which red flags to watch for and when you should expect to feel better on an antibiotic.
If you’re on an antibiotic and don’t feel better after a few days, tell your doctor so they can reassess.
The key takeaways were created with the assistance of generative AI. An AARP editor reviewed and refined the content for accuracy and clarity.
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