Doxycycline does not directly cause weight gain. However, because it eliminates all bacteria including gut bacteria that is responsible for weight control and inflammation, it may temporarily increase your weight. However, any added weight gain should go away after you complete your dose of antibiotics.
At higher doses doxycycline also acts as an antibiotic for which it has been clinically used for decades. A previous clinical study found that taking doxycycline twice a day, for one week after a heart attack improved the health of the patients’ hearts.Apr 25, 2018