Bitterness in the mouth after taking Clarithromycin is a normal phenomenon, and Clarithromycin tablets themselves have side effects in this regard. Some other side effects of clarithromycin are bad taste in the mouth and gastrointestinal reactions such as diarrhea, stomach pain, nausea and vomiting. Taking clarithromycin may also cause headache or transient increase of serum transaminase. Because clarithromycin is an antibacterial drug that is mainly used to treat lung infections or infections in other areas, it should also not be applied for a long time, which can lead to these side effects above. If your mouth is bitter, you can drink honey water or eat sugar after eating to relieve it.