Antibiotics are designed to kill harmful bacteria that cause conditions like urinary tract infections (UTIs), sinus infections, eye infections, skin infections and pneumonia. While antibiotics seem like straightforward medications, their side effects can be problematic. Some people may have no trouble taking an antibiotic, while others may wind up feeling even more rundown once they begin taking the medicine that is supposed to help them get better.

People are usually most familiar with the bothersome effects that antibiotics can have on the digestive system. For example, azithromycin (sold under the brand names Z-Pak, Zithromax and Zmax) most frequently causes upset stomach, diarrhea and vomiting. But, a lesser known side effect of azithromycin and other common antibiotics, such as amoxicillin and ciprofloxacin, is serious fatigue.

While the exact reason for this side effect isn’t fully understood, it could have something to do with how antibiotics alter the balance of microbes in our bodies. These medications often alter or kill off good bacteria in the body along with the bad. This can cause changes in the digestive system that affect nutrient absorption and can contribute to fatigue and lethargy.


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If there is a specific medication, whether it is an antibiotic or not, that affects you or your aging loved one adversely, it’s important to take note of this and report it to your doctor. The physician has weighed the risks and benefits of this drug and prescribed it for a reason, but it is important to follow up with them if it is causing serious side effects. It could indicate an adverse reaction or that it isn’t the right drug for the “bug” that is responsible for the initial illness. Even if it is just a bothersome side effect, the doctor should be able to add this to the patient’s notes for future reference and suggest a different drug.

Antibiotics are incredibly helpful for fighting dangerous infections, but it is important to only take them when they are needed and follow the prescription instructions exactly. Overuse and misuse of these drugs can cause more harm than good.