Cod liver oil

Cod liver oil: EPA and DHA combined with retinol (vitamin A) and cholecalciferol (vitamin D3); registered as a medicine in Spain

ATC code: C10AX-COD-LIVER (Cod liver oil (EPA/DHA plus retinol and vitamin D3))

Brand names

Carlson Norwegian Cod Liver Oil, Nordic Naturals Arctic Cod Liver Oil, Twinlab Norwegian Cod Liver Oil, Seven Seas Original Cod Liver Oil

Mechanism of action

Cod liver oil differs from standard fish oil because it is extracted not from muscle but from the liver of cod (Gadus morhua), which concentrates fat-soluble vitamins. A teaspoon (4–5 mL) provides roughly 800–1200 mg EPA+DHA, around 1000–1500 mcg of retinol (vitamin A) and 400–1000 IU of vitamin D3 – exact figures depend on the producer and country. In Spain AEMPS registers Aceite de Higado de Bacalao as a medicinal product for prevention of vitamin A and D deficiency in children with insufficient dietary intake. In most EU countries and the US it is sold as a supplement. The main clinical limit is vitamin-A hypervitaminosis with long-term high doses: retinol accumulates in the liver, sets the adult Tolerable UL at 3000 mcg RE per day and the limit is stricter in pregnancy. Modern paediatricians prefer separate vitamin D3 preparations without a retinol load.

Indications

Rickets in children

Adjunct

Cod liver oil received historical registration as a rickets-prophylaxis product in children in the early twentieth century when vitamin D deficiency and lack of sun exposure were widespread. AEMPS in Spain still registers Aceite de Higado de Bacalao as a medicine for prevention of vitamin A and D deficiency in children with insufficient dietary intake. Modern paediatrics ( 2008/2010, AEP, Endocrine Society 2024, Spanish SEEN 2024) recommends pure cholecalciferol (vitamin D3) 400 IU/day from the first days of life on breastfeeding for rickets prevention; these preparations carry no retinol load. Cod liver oil remains a workable option but is not first line. In schoolchildren and adolescents D3 drops or tablets are also preferred. If cod liver oil was prescribed for rickets prevention, check the vitamin D dose against the 400–600 IU/day requirement; excess retinol is undesirable.

Sources

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

Immune support and respiratory infection care

Not recommended

Cod liver oil supplies omega-3 fatty acids and vitamins A and D, and it's promoted to strengthen immunity and ward off colds and respiratory infections. So far studies haven't shown a convincing benefit for this use: the supplement doesn't cut how often you catch seasonal infections or how long they last. The oil itself is safe in this role. To prevent respiratory infections, other measures work – flu vaccination, hand hygiene and enough sleep, and a vitamin D deficit is worth correcting only after a blood test.

Sources

Vitamin D deficiency

Not recommended

Cod liver oil has historically been used as a vitamin D source in confirmed deficiency. Modern endocrinology societies (Endocrine Society 2024, Spanish SEEN 2024) treat 25(OH)D deficiency with pure cholecalciferol at a dose individualised to the blood test – usually 1000–4000 IU/day maintenance or a short course of 50 000 IU/week for 6–8 weeks in severe deficiency. Cod liver oil delivering the same vitamin D dose also provides an extra 1000–1500 mcg of retinol; long-term use can exceed the adult Tolerable UL (3000 mcg RE/day) when combined with dietary sources (liver, egg yolks, fortified foods) and raises the risk of vitamin A hypervitaminosis. If cod liver oil was bought to treat vitamin D deficiency, discuss with a doctor switching to pure D3, especially for long-term use and risk groups (older adults, pregnant women, women with osteoporosis).

Sources

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Safety

Contraindications

Pregnancy (retinol teratogenic risk)
History of vitamin A hypervitaminosis
Severe hepatic impairment (retinol accumulates)
Known fish allergy
High-dose warfarin therapy
Concurrent systemic retinoids (isotretinoin, acitretin)

Serious adverse effects

Vitamin A hypervitaminosis with long-term high-dose use: skin dryness, hair loss, bone pain, raised intracranial pressure, hepatic dysfunction
Teratogenic effect if taken during pregnancy
Severe allergic reactions in fish-allergic patients
Bleeding amplification when combined with anticoagulants

Common adverse effects

Fishy-tasting eructation
Gastrointestinal discomfort
Aftertaste and nausea on empty stomach

PregnancyFDA X

Cod liver oil at standard adult doses is contraindicated in pregnancy: retinol is teratogenic above 3000 mcg RE/day (Rothman NEJM 1995 showed increased risk of CNS, facial and cardiac malformations). Pregnant women with vitamin D deficiency receive pure D3 at an individualised dose without a retinol load. If cod liver oil was taken before pregnancy, discuss with a doctor switching to pure D3 and monitoring vitamin A levels.

Breastfeeding

High-dose retinol from cod liver oil transfers into human milk during lactation. Mothers with confirmed vitamin D deficiency are better treated with pure D3. Standard paediatric doses of cod liver oil in breastfed infants are acceptable when prescribed by a paediatrician.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Cod liver oil used for?

Cod liver oil is evaluated for the following indications with varying evidence strength: Rickets in children (evidence tier B), Immune support and respiratory infection care (evidence tier D), Vitamin D deficiency (evidence tier D). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Cod liver oil?

Common side effects of Cod liver oil (≥ 1 in 100): Fishy-tasting eructation, Gastrointestinal discomfort, Aftertaste and nausea on empty stomach. See the Safety section for uncommon and serious reactions.

Is Cod liver oil safe during pregnancy?

FDA category X. Cod liver oil at standard adult doses is contraindicated in pregnancy: retinol is teratogenic above 3000 mcg RE/day (Rothman NEJM 1995 showed increased risk of CNS, facial and cardiac malformations). Pregnant women with vitamin D deficiency receive pure D3 at an individualised dose without a retinol load. If cod liver oil was taken before pregnancy, discuss with a doctor switching to pure D3 and monitoring vitamin A levels.

Is Cod liver oil compatible with breastfeeding?

Who should not take Cod liver oil?

Cod liver oil is contraindicated in: Pregnancy (retinol teratogenic risk); History of vitamin A hypervitaminosis; Severe hepatic impairment (retinol accumulates); Known fish allergy; High-dose warfarin therapy. Full list in the Safety section.

Mechanism of action

Indications

Rickets in children

Adjunct

Sources

Safety

Contraindications

Pregnancy (retinol teratogenic risk)
History of vitamin A hypervitaminosis
Severe hepatic impairment (retinol accumulates)
Known fish allergy
High-dose warfarin therapy
Concurrent systemic retinoids (isotretinoin, acitretin)

Serious adverse effects

Vitamin A hypervitaminosis with long-term high-dose use: skin dryness, hair loss, bone pain, raised intracranial pressure, hepatic dysfunction
Teratogenic effect if taken during pregnancy
Severe allergic reactions in fish-allergic patients
Bleeding amplification when combined with anticoagulants

Common adverse effects

Fishy-tasting eructation
Gastrointestinal discomfort
Aftertaste and nausea on empty stomach

PregnancyFDA X

Breastfeeding

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Cod liver oil used for?

What are the side effects of Cod liver oil?

Is Cod liver oil safe during pregnancy?

Is Cod liver oil compatible with breastfeeding?

Who should not take Cod liver oil?