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Is it safe to work out when you’re taking antibiotics?

If you’ve ever been prescribed antibiotics, you may know there’s a list of things you might need to avoid while you’re taking them: alcohol, grapefruit juice, antacids or calcium supplements, and certain other prescription medications, like blood thinners.

One thing you probably never thought twice about doing while on antibiotics, though, is working out. Exercise is good for your immune system…why would you stop doing it while recovering from an infection? 

Well, because some antibiotics can cause side effects that may affect your ability to do vigorous exercise. Whether you’re a regular gym rat, a weekend athlete, an occasional spin class enthusiast, or a marathon runner-in-training, here’s what you need to know about working out on antibiotics.

Is it safe to exercise while taking antibiotics? 

The short answer is, generally, yes: Most antibiotics are safe to take while engaging in normal types of exercise, given that you’re otherwise healthy and feel well enough to work out. However, you should keep in mind that your body is not operating at its best when you have an infection, so there are some things to consider first.

“Any infection will put stress on the body,” says Michael Billet, MD, an emergency department physician at Mercy Medical Center in Baltimore. “How this affects the patient will depend on a lot of factors, like the type of infection, its severity, and the patient’s baseline health or other medical issues.”

There is one major class of antibiotics to watch out for when it comes to working out, and it’s fluoroquinolones. This class of antibiotics, which includes ciprofloxacin (Cipro), can be used to treat respiratory, skin, and urinary tract infections, but they also carry a serious risk of sports injury.

“Fluoroquinolones [can cause weakened] tendons, and, when combined with vigorous exercise or weight-bearing can lead to strains, sprains, and even tendon rupture,” warns Dr. Billet, who adds that these side effects are most common when fluoroquinolones are taken in high doses or for a long duration, although short courses of treatment shouldn’t be overlooked either.

What’s more, unlike most antibiotics—which are cleared fairly quickly from the body—fluoroquinolones can still cause injury after you’ve stopped taking them.

“I don’t prescribe them to athletes [because] even being off of them, there’s an associated risk of tendon injury for a long time afterward,” says Joshua Scott, MD, a primary care sports medicine physician at Cedars-Sinai Kerlan-Jobe Institute in Los Angeles.

A 2014 review published in the Journal of Athletic Training reports that fluoroquinolones have the potential to cause tendinitis, tendon pain, or rupture up to six months after discontinuing their use.

Do the recommendations change based on the type of exercise you’re doing?

Not usually. The type of exercise is less important than the type of antibiotic; if you’re on fluoroquinolones, you shouldn’t be doing any kind of moderate or intense exercise, but those activities are typically safe while taking most other classes of antibiotics.

In other words, exercises that are normal for you—whether it’s weightlifting, running, or yoga—are okay to continue doing when you’re on antibiotics like penicillin or azithromycin, as long as you feel up to it. If you’re not sure how your medication can affect your workout routine, just ask your doctor.

“A lot of doctors use the most commonly recommended antibiotic for an infection without taking into account that someone is a crossfit trainer, runs 40 miles per week, or has an active lifestyle,” says Dr. Scott, who advises letting your doctor know if you exercise more than the average person before leaving with a prescription.

What are the side effects of working out while taking antibiotics? 

Aside from the risk of sports injury with fluoroquinolones, there are a few other side effects to keep in mind. 

“Antibiotics most commonly affect the GI tract, causing upset stomach and nausea, which could make it difficult to stay well hydrated,” says Dr. Billet. “These side effects are probably the biggest issue aside from the infection itself.”

As for whether a course of antibiotics can affect your athletic performance or worsen your fatigue, there’s more anecdotal evidence than actual scientific evidence. Dr. Scott says some studies have shown that the relationship between fatigue and antibiotic use may be higher with certain ones, like doxycycline, but an old study from 1993, conducted on military trainees, found no connection between perceived fatigue and antibiotic use.

Don’t forget that your body will be working hard alongside those antibiotics to fight off the infection—and that can make you feel more tired than usual, too.

Can antibiotics interact with workout supplements?

In theory, yes. Dr. Scott says that many foods, drinks, and supplements can affect how well antibiotics work, so it’s important to talk to your doctor about any workout supplements you’re taking before they prescribe you an antibiotic. 

If you’re still uncertain, it’s better to refrain from using any supplements until you’ve finished your antibiotics. Supplements often contain herbs or ingredients that can interact with other medications

“Workout supplements frequently contain caffeine, which can alter the effectiveness of the antibiotic,” says Dr. Billet, “and regulation-wise, many workout supplements fall into a grey zone of not quite food, not quite medicine—so even from a reputable vendor you don’t exactly know what you’re getting.”

Why it’s important to rest when recovering from an infection 

Even if you can exercise on antibiotics, it doesn’t mean you should. Although exercise is a great way to boost your immune system, Dr. Scott says that resting while you’re being treated for an infection is also a great time to take a break…and that you’ll usually get better faster if you rest.

“When your immune system is having to fight across several different fronts—you’re taking an antibiotic, fighting a sinus infection, and utilizing muscles [during exercise] that have to be repaired and restored—that can all be hard on the body and delay recovery,” he explains.

Instead of continuing to work out at your usual frequency or intensity, use the time to sleep, stay hydrated, and eat well. Dr. Scott adds that you may also want to add a probiotic to your diet, to offset any gastrointestinal distress caused by the antibiotic.