Good news: You might be able to shorten the time you take antibiotics. For decades, doctors have advised patients to take the drugs for at least a week or two, even if they feel better after just a few days. But a new study adds to a growing body of evidence suggesting that, in some cases, a shorter course of antibiotics works just as well—and is safer.

In the study, published July 25 in JAMA Internal Medicine, Spanish researchers examined the use of antibiotics in 312 adults who had bacterial pneumonia severe enough to require hospitalization. The approximately half of patients randomized to “standard care” wound up taking antibiotics for an average of 10 days. In the other half, doctors stopped the drugs after 5 days as long as the patients didn’t have a fever and appeared to be on the mend.

Ten days after the start of treatment, researchers found that patients who stopped the drugs early were faring just as well as those who kept taking them; after a month, the vast majority of both groups had recovered. In fact, only 1.4 percent of patients in the short-treatment group wound up being readmitted to the hospital within 30 days, compared to 6.6 percent of those who took antibiotics for twice as long.

Previous research has shown that a short course of treatment also works well against mild-to-moderate cases of pneumonia in patients treated outside the hospital.

So is the same true for other types of infections?

“Unfortunately, there aren’t a lot of other high-quality studies that have examined the ideal length of therapy for infections,” says Lauri Hicks, D.O., a medical epidemiologist at the Centers for Disease Control and Prevention (CDC) and head of the agency’s program Get Smart: Know When Antibiotics Work. But it's telling that most of the research that has asked “how long does it take for antibiotics to work?” has discovered that it's less time than once thought. Those studies are summarized in the table below.

“Historically, the perception has been that longer treatment with antibiotics is better or safer,” says Hicks. “That’s an assumption we really need to challenge.”

When Shorter Therapy Can Be Just as Effective

Disease

Longer Treatment (days)

Equally Effective Shorter Treatment (days)

Abdominal infection

10

4
Bronchitis in people with Chronic Obstructive Pulmonary Disease (COPD)

7 or more

5 or fewer

Bacterial sinus infection

10

5
Cellulitis (skin infection)

10

5 to 6

Chronic bone infection

84

42

Kidney infection

10 to 14

5 to 7

Pneumonia acquired in the hospital

10 to 15

8 or fewer

Pneumonia acquired outside the hospital

10 to 14

3 to 5

"The New Antibiotic Mantra: "Shorter is Better," JAMA Internal Medicine, July 25, 2016.

Why Shorter Can Be Safer

Antibiotics can be life-saving drugs, but there are good reasons not to take the powerful germ killers longer than you have to. “It increases your risk of common side effects such as rashes and diarrhea,” says Hicks. “We are especially concerned that a longer course of treatment increases the risk of a Clostridium difficile, or C. diff, infection, a sometimes deadly diarrhea that is usually a direct consequence of antibiotic use.”

Healthcare providers have traditionally prescribed longer courses of antibiotics to be extra sure to wipe out all the disease-causing germs. But as scientific understanding has evolved, it's become clear that the drugs affect not only the bacteria that caused the infection, but also the complex ecosystem of trillions of other bacteria inhabiting the human body.

"Research shows that the longer you take an antibiotic, the more likely bacteria living in and on your body are to become resistant, or immune, to that drug,” says Hicks. If at some point those hardy bacteria “flare up” and cause an infection, it can be harder to treat, she says. And you can also pass those resistant bacteria along to the people around you.

“Overtreating people with antibiotics is one of the factors that has led to the public health crisis of antibiotic resistance, where once effective antibiotics no longer work against many common infections,” says Hicks.

Of course, undertreating an infection also has consequences as surviving bacteria can multiply and make you even sicker than you were to begin with. “I have sympathy for healthcare providers who prescribe a longer course of antibiotics to be on the safe side, hoping to ensure that their patients get better,” says Hicks. But she says that once the antibiotics have done their job against the active infection, there’s no benefit—only an increasing risk of potentially dangerous side effects—if you continue to take them.    

Don't Stop Without Talking to Your Doc

Some serious infections such as tuberculosis and those affecting the bones, heart valves, or bloodstream require long courses of medication. “In certain circumstances, you can start to feel better, but still have an active infection that requires treatment,” Hicks says.

If you are taking an antibiotic for a more garden-variety illness such as a sinus infection, urinary tract infection, or pneumonia, Hicks says it’s “very reasonable” to call your doctor and ask if you can discontinue the drug once you have been free of fever for 48 hours and are feeling significantly better.

Just don't hang on to leftover antibiotics. Discard unused medication by returning it to the pharmacy or a community take-back program. Or mix the medication with an unpalatable substance such as kitty litter or coffee grounds, seal it in a bag, and throw it out with the household trash. Read more about safe ways to dispose of antibiotics and other unwanted medicines.

Editor's Note: These materials are made possible by a grant from the state Attorney General Consumer and Prescriber Education Grant Program, which is funded by the multi-state settlement of consumer-fraud claims regarding the marketing of the prescription drug Neurontin (gabapentin).