4 known interactions • 1 major • 2 moderate • 1 minor
Always disclose all medications to your healthcare providers — prescription medicines, OTC medications, vitamins, and herbal supplements. This list may not include every possible interaction. Use our Medicine Interaction Checker to screen your complete medication list.
Potentially life-threatening or causing permanent damage. Avoid combination.
May worsen condition or require dose adjustment. Monitor closely.
Usually limited clinical effect. Manage with routine monitoring.
Isotretinoin
Both tetracyclines and isotretinoin independently increase intracranial pressure (pseudotumor cerebri). Combination dramatically increases this risk.
Management: Contraindicated — do not use doxycycline with isotretinoin.
Calcium / antacids / iron / dairy products
Divalent and trivalent cations chelate doxycycline in the GI tract, reducing absorption by up to 80%.
Management: Take doxycycline 1–2 hours before or after calcium, antacids, iron supplements, or dairy products. (Doxycycline is less affected by dairy than older tetracyclines, but absorption is still reduced.)
Warfarin
Doxycycline can increase anticoagulant effect via gut flora changes reducing vitamin K production.
Management: Monitor INR when starting doxycycline; anticoagulant dose may need adjustment.
Oral contraceptives
Historical concern, but evidence suggests doxycycline does NOT significantly reduce OCP efficacy in most patients.
Always ask your pharmacist about potential interactions with food, alcohol, and supplements specific to Doxycycline. Some medicines have significant interactions with grapefruit juice, high-fat meals, dairy products, or vitamin K-rich foods.