Omega-3 and Your Medications

Key overview

  • Fish oil affects bleeding time. That is the interaction that matters most.
  • Tell your surgeon you take it, well before any operation. Many ask patients to stop beforehand.
  • If you take warfarin, a DOAC, aspirin or clopidogrel, ask your prescriber before starting.
  • This page is general information. Your prescriber knows your medication list and this page does not.

Omega-3 is well tolerated and available without prescription, which leads people to assume it is inert. It is not, and there is one interaction worth taking seriously.

Bleeding time

Omega-3 fatty acids have an antiplatelet effect — they modestly reduce how readily platelets aggregate. At the doses used for general health this is rarely clinically significant on its own. It becomes worth attention when it is added to something else doing the same thing.

Ask your prescriber before starting if you take:

  • Warfarin — the combination is used, but it warrants a conversation and possibly closer INR monitoring at the outset.
  • Direct oral anticoagulants such as rivaroxaban, apixaban or dabigatran.
  • Antiplatelets — aspirin, clopidogrel, ticagrelor.
  • Regular NSAIDs at anti-inflammatory doses.

This is not a list of prohibitions. Many people take fish oil alongside these safely. It is a list of situations where the decision belongs to whoever manages your medication. Our article on fish oil and bleeding covers the evidence in more depth.

Surgery

This is the one people forget. Many surgeons ask patients to stop fish oil for a period before an operation, and the request is only useful if they know you take it.

Tell the surgical team about every supplement at the pre-operative appointment, not on the day. That matters for eye surgery specifically — if you are taking omega-3 for dry eye and are also having cataract or refractive surgery, the two conversations are with the same people and should happen together.

Other things worth mentioning

  • Blood pressure medication — omega-3 can have a small blood-pressure-lowering effect. Additive rather than dangerous, but worth flagging if yours runs low.
  • Diabetes medication — effects on glycaemic control are small and inconsistent; mention it, and do not change anything on your own.
  • Vitamin A — relevant to cod liver oil rather than to concentrated fish oil, but worth checking the label if you are taking a general fish oil and are pregnant.

Allergy

Fish and shellfish allergy is the obvious contraindication for fish-derived oils. Algal omega-3 is an alternative that provides DHA and some EPA without the fish source; it is also the option for anyone vegan. Flaxseed is not equivalent — it supplies ALA, which humans convert to EPA and DHA inefficiently.

Pregnancy and breastfeeding

Omega-3 is commonly recommended in pregnancy, but the product matters and the decision belongs to your midwife or doctor. Do not start a supplement on the strength of a page about eyes. See dry eye in pregnancy for the conservative approach.

The general point

Tell whoever prescribes for you what you are taking, including things bought off a shelf. Supplements are routinely omitted from medication lists because people do not count them as medicine, and that omission is where most avoidable interactions come from.

Part of our guide to Omega-3 & Eye Nutrition.