Is doxycycline a safe antibiotic? any percautions i should take, and does it affect electrolytes?

Safe: It's a safe drug, but avoid too much sun exposure, because it can make your skin more sensitive to the sun. You don't need to worry about you electrolytes.

Potential danger: Doxycycline is known to cause a potentially dangerous condition known as drug-induced esophagitis. The esophagus is the tube between the throat and the stomach. If a capsule gets stuck in the esophagus and lays against the delicate lining of the esophagus, it dissolves slowly and can erode into the lining of the esophagus. Drinking lots of water after taking doxcycline can prevent this.