SN instructed that doxycycline is a tetracycline antibiotic. It fights bacteria in the body. Take doxycycline exactly as prescribed by your doctor. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended. Take doxycycline with a full glass of water. Drink plenty of liquids while you are taking this medicine. Most brands of doxycycline may be taken with food or milk if the medicine upsets your stomach. Different brands of doxycycline may have different instructions about taking them with or without food. Take Oracea on an empty stomach, at least 1 hour before or 2 hours after a meal.Call your doctor at once if you have: changes in your vision; severe stomach pain, diarrhea that is watery or bloody, fever, swollen glands, body aches, flu symptoms, weakness, skin rash, pale skin, easy bruising or bleeding, severe tingling, numbness, pain, muscle weakness; upper stomach pain ( may spread to your back ), loss of appetite, dark urine, jaundice ( yellowing of the skin or eyes ); chest pain, irregular heart rhythm, feeling short of breath; confusion, nausea and vomiting, swelling, rapid weight gain, little or no urinating; new or worsening cough with fever, trouble breathing;increased pressure inside the skull - skin pain, followed by a red or purple skin rash that spreads ( especially in the face or upper body ) and causes blistering and peeling. Severe headaches, ringing in your ears, dizziness, nausea, vision problems, pain behind your eyes; or severe skin reaction - fever, sore throat, swelling in your face or tongue, burning in your eyes.