Doxycycline has been specially developed for the treatment of infections caused by bacteria - such as Lyme disease, pneumonia, genital infections and urinary system infections. Make sure you discuss all the aspects of your treatment with your health care provider. Mention the fact of using any other medications that may affect the success of your treatment, as well as the fact of ever been diagnosed with liver or kidney disease. A dose adjustment may be required if you have any of the conditions mentioned. Take the entire amount of doxycycline prescribed, as otherwise you may not benefit from the treatment as much. Tell your health care provider if you get any of the following serious side effects of doxycycline: peeling, urinating less than usual, body aches, loss of appetite, severe headache, severe blistering, pale or yellowed skin, blurred vision, yellowing of the skin or eyes, severe pain in your upper stomach, flu symptoms, confusion or weakness, red skin rash, dizziness, and easy bruising or bleeding. Less serious side effects are a lot less likely and include sore mouth, swollen tongue, vomiting, vaginal itching, sores or swelling in your rectal or genital area, diarrhea, stomach upset, mild nausea, or trouble swallowing.