-Antacids, vitamins, or other products that contain aluminum, calcium, iron, magnesium, or zinc
-Barbiturates
-Bismuth subsalicylate
-Carbamazepine
-Estrogen or progestin hormones
-Methoxyflurane
-Oral retinoids, such as acitretin, isotretinoin
-Other antibiotics
-Phenytoin
-Warfarin

They need to know if you have any of these conditions:
-Kidney disease
-Liver disease
-Long exposure to sunlight like working outdoors
-Recent stomach surgery
-Stomach or intestine problems, such as colitis
-Vision problems
-Yeast or fungal infection of the mouth or vagina
-An unusual or allergic reaction to doxycycline, other medications, foods, dyes, or preservatives
-Pregnant or trying to get pregnant
-Breastfeeding

Tell your care team if your symptoms do not improve.
Do not treat diarrhea with over the counter products. Contact your care team if you have diarrhea that lasts more than 2 days or if it is severe and watery.
Do not take this medication just before going to bed. It may not dissolve properly when you lay down and can cause pain in your throat. Drink plenty of fluids while taking this medication to also help reduce irritation in your throat.
This medication can make you more sensitive to the sun. Keep out of the sun. If you cannot avoid being in the sun, wear protective clothing and sunscreen. Do not use sun lamps, tanning beds, or tanning booths.
Estrogen and progestin hormones may not work as well while you are taking this medication. A barrier contraceptive, such as a condom or diaphragm, is recommended if you are using these hormones for contraception. Talk to your care team about effective forms of contraception.
If you are being treated for a sexually transmitted infection (STI), avoid sexual contact until you have finished your treatment. Your sexual partner may also need treatment.
If you are using this medication to prevent malaria, you should still protect yourself from contact with mosquitos. Stay in screened-in areas, use mosquito nets, keep your body covered, and use an insect repellent.

Keep out of the reach of children and pets.
Store at room temperature, below 30 degrees C (86 degrees F). Protect from light. Keep container tightly closed. Throw away any unused medication after the expiration date. Taking this medication after the expiration date can make you seriously ill.