Omega-3 fatty acids Pregnancy: No adequate data in pregnant women; animal studies have not shown reproductive toxicity but the potential risk for humans is unknown — should not be used during pregnancy unless clearly necessary. Should not be used during lactation (no data on excretion in milk)

Omega-3-acid ethyl esters

Brand names: Omacor

Omega-3-acid ethyl esters are a lipid-regulating preparation of eicosapentaenoic and docosahexaenoic acid ethyl esters, used as an adjunct in severe hypertriglyceridaemia.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Hypertriglyceridaemia: two capsules (1000 mg strength) daily

Route: Oral

Frequency: Daily; capsules may be taken with food to avoid gastrointestinal disturbances

Max: Four capsules daily

If an adequate response is not obtained, the dose may be increased to four capsules daily. Because of the moderate increase in bleeding time at the high dosage (4 capsules per day), patients on anticoagulant therapy must be monitored and the anticoagulant dose adjusted if necessary; make allowance for increased bleeding time in patients at high risk of haemorrhage (severe trauma, surgery). Monitor ALT and AST in patients with any signs of liver damage, particularly at the high dosage. Systematic reviews show a dose-dependent increased risk of atrial fibrillation in patients with established cardiovascular disease or risk factors, highest at 4 g daily — if atrial fibrillation develops, treatment should be permanently discontinued. Not indicated in exogenous hypertriglyceridaemia (type 1 hyperchylomicronaemia); only limited experience in secondary endogenous hypertriglyceridaemia (especially uncontrolled diabetes) and no experience in combination with fibrates. Limited clinical data in people over 70 years and in renal impairment; no information in hepatic impairment. Paediatric: no information in children and adolescents — in the absence of efficacy and safety data, use is not recommended (no per-kg dose stated). Source product: Omega 3-acid ethyl esters 1000 mg soft capsules.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients

Side effects

Atrial fibrillation (common)
Gastrointestinal disorders (common) — abdominal distension, abdominal pain, constipation, diarrhoea, dyspepsia, flatulence, eructation, gastro-oesophageal reflux disease, nausea or vomiting
Dizziness, dysgeusia, headache (uncommon)
Hyperglycaemia, gout (uncommon); hypotension, epistaxis, gastrointestinal haemorrhage (uncommon)
Liver disorders including increased transaminases (rare); hypersensitivity, urticaria (rare); rash (uncommon), pruritus (frequency not known)

Interactions

Oral anticoagulants: prothrombin time must be checked when combined with warfarin, and the anticoagulant dose adjusted if necessary (omega-3-acid ethyl esters have been given with warfarin without haemorrhagic complications)
Use with caution in patients with known sensitivity or allergy to fish

Clinical monograph

How it works

They reduce hepatic synthesis of triglycerides and very-low-density lipoprotein, lowering serum triglyceride concentrations; the precise mechanisms include effects on fatty acid metabolism and substrate availability.

Prescribing in practice

They may modestly prolong bleeding time and should be used with caution in patients on anticoagulants or antiplatelet agents and around surgery.
Routine post-myocardial-infarction use is no longer generally recommended, as later evidence did not confirm a consistent cardiovascular benefit for this preparation; its main role is in hypertriglyceridaemia.
Caution is advised in those with fish or seafood allergy and in hepatic impairment; consult the SPC.

Monitoring

Monitor the fasting lipid profile, and liver function where there is hepatic impairment.

Counselling the patient

Advise taking the capsules with food to reduce indigestion and fishy aftertaste.
Tell the patient to mention this medicine before any surgery or if they take blood-thinning drugs.

Evidence & guidelines

Omega-3-acid ethyl esters lower triglycerides but later trials did not confirm broad cardiovascular benefit for this preparation; refer to current prescribing references.

Reference: NICE CG181; Confirm identity and dosing against the manufacturer SPC (eMC) and NICE. Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways