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In a study that appeared in the 2004 Annals of Pharmacotherapy, krill oil increased the effect of warfarin, a blood-thinning medication. Additional medications that may interact with krill oil include aspirin, clopidogrel, diclofenac, ibuprofen, naproxen, dealteparin, enoxaparin, heparin and warfarin. You should, therefore, speak with a medical professional prior to taking any krill oil supplement if you currently take any medication that can cause your blood to thin.
Many individuals have a food allergy to crustaceans, and Krill are a type of very small crustacean. If you have an allergy to crustaceans, you should not consume krill oil. If you have a crustacean allergy, you will generally have a moderate to extreme allergic reaction to krill oil. This allergic reaction may require emergency care and or hospitalization. Even if you normally do not have any known allergy to crustaceans, if you experience any allergic reaction to a krill oil supplement, immediately discontinue use and seek medical attention