Doxycycline can be recommended for patients with bacterial infections - such as acne, urinary system infections, genital infections and some other ones. You are not supposed to be taking doxycycline if you are allergic to it or any other medications of the kind, such as minocycline, tetracycline or sulfites. Report any other medications you are taking that can interact with doxycycline and in some way affect the success of your treatment. The following medications are supposed to be mentioned if you are taking them at the moment or there is a chance you will start taking them in the nearest future: blood thinner, isotretinoin, minerals, cholesterol-lowering medications, tretinoin, penicillin antibiotics, over-the-counter vitamin and mineral supplements, as well as antacids. Your doctor will recommend taking doxycycline a certain way that will not affect the efficiency of the other treatment, and vice versa. Tell your doctor about any side effects that seem serious enough to be reported - such as severe headache, severe pain in your upper stomach, loss of appetite, dizziness, blurred vision, red skin rash, confusion or weakness, flu symptoms, urinating less than usual, pale or yellowed skin, yellowing of the skin or eyes, severe blistering, body aches, peeling, or easy bruising or bleeding.