Tiredness is not listed as a general side effect of taking antibiotics, according to Drugs.com. However, quinolones, a type of antibiotic used to treat a wide range of conditions, do list lethargy as a potential side effect.
General side effects of taking antibiotics include abdominal pain, vomiting, diarrhea, rash, nausea, fever, hypersensitivity and photosensitivity. Women sometimes experience vaginal yeast infections when taking certain types of antibiotics.
Children under a year of age have the highest rate of adverse reaction to antibiotics, according to Drugs.com. Since 2008, an estimated 140,000 people per year visit the emergency room due to adverse reactions to antibiotics.