Cod Liver Oil: Omega-3 Plus Vitamins A and D
Cod liver oil supplies omega-3 plus vitamins A and D in amounts that vary by product. See the NHS pregnancy warning, vitamin A limits, what trials found, and why it is not fish oil.
Content last updated . This page has not been medically reviewed.
What is Cod liver oil good for?
What the body uses it for, and how strong the evidence is. A normal job in the body is not proof that extra supplements add benefit; each card says which.
Source of EPA and DHA omega-3
Established roleCod liver oil provides the marine omega-3 fats EPA and DHA, alongside vitamins A and D.
Supplements: Normal body roles of omega-3 are not proof that supplements help; benefit depends on the outcome and many trials used fish oil.
Vitamin D for bones, teeth and muscles
Established roleVitamin D helps regulate calcium and phosphate, which keep bones, teeth and muscles healthy.
Supplements: Supplements correct low vitamin D; benefit when intake is adequate is not shown here.
Vitamin A for vision in dim light
Established roleVitamin A helps you see in dim light.
Supplements: Useful only for those low in vitamin A; the NHS advises keeping total intake at or below 1.5 mg a day.
Triglyceride lowering (marine omega-3)
Preliminary or mixedA review of 23 studies found EPA and DHA lowered triglycerides by about 15%.
Supplements: Prescription-strength EPA/DHA is a regulated medical use; ordinary cod liver oil has not been shown to do the same.
Heart health research
Preliminary or mixedSome analyses of marine omega-3 supplements found fewer heart attacks and coronary deaths.
Supplements: Mixed evidence; none of the sources I read tested cod liver oil for heart events.
Joint pain and swelling in rheumatoid arthritis
Preliminary or mixedReviews suggest omega-3-rich foods may ease joint pain and swelling, but the evidence is low quality.
Supplements: Do not change prescribed medicines; evidence is low quality.
Dry eye
Preliminary or mixedSmall studies suggested benefit, but the NIH-sponsored DREAM trial of 535 people found omega-3 no better than placebo.
Supplements: Large trial was negative.
Mood and depression
Not enough evidenceEvidence is uncertain; any effect may be too small to matter and the evidence quality is low or very low.
Supplements: No reliable benefit shown.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (2)
- Bone HealthEstablished role
Vitamin D in the oil supports calcium handling for bones. This matters mainly for people low in vitamin D; vitamin A too high may harm bones.
- Heart HealthPreliminary or mixed
Its EPA and DHA are studied for heart health; the evidence is mixed and is mostly from fish oil rather than cod liver oil.
Body systems (3)
- Bones, Joints & MusclesEstablished role
Cod liver oil can supply vitamin D, which helps regulate calcium and phosphate for healthy bones, teeth and muscles. The amount varies by product, and too much vitamin A over many years may weaken bones.
- Cardiovascular SystemPreliminary or mixed
Its EPA and DHA are studied for heart disease and triglycerides, but the sources do not single out cod liver oil. Evidence is mixed.
- Heart & CirculationPreliminary or mixed
Its EPA and DHA are studied for heart health, but the large reviews mostly covered fish oil, not cod liver oil. Evidence for supplements is mixed.
Body parts (3)
- BonesEstablished role
The vitamin D in cod liver oil helps keep bones healthy; lack of vitamin D can cause rickets and osteomalacia. Long-term high vitamin A intake may raise fracture risk in later life.
- EyesEstablished role
The vitamin A in cod liver oil is needed for vision in dim light. Omega-3 supplements did not beat placebo for dry eye in the large NIH-sponsored DREAM trial.
- HeartPreliminary or mixed
Marine omega-3s are studied for heart disease; some analyses found fewer heart attacks, but cod liver oil itself was not singled out.
Functional actions (1)
- Cardiovascular SupportPreliminary or mixed
Marine omega-3s are researched for heart and triglyceride effects. Results are mixed and not specific to cod liver oil.
Root causes (1)
- Nutrient DeficiencyDeficiency link
Cod liver oil supplies vitamins A and D, whose lack causes known problems such as rickets and osteomalacia. It helps only where intake is low, and the amounts vary by product.
Biomarkers (1)
- TriglyceridesPreliminary or mixed
A 2020 review found EPA and DHA lowered triglycerides by about 15%. That review did not test cod liver oil specifically, which gives less EPA and DHA than purified products.
Conditions & symptoms (3)
- HypervitaminosisDocumented risk
Vitamins A and D in fish liver oil can be harmful in excess; long-term high vitamin A may affect bones.
- HypercalcemiaDocumented risk
Long-term overuse of vitamin D supplements can cause hypercalcaemia. Cod liver oil adds vitamin D.
- HypertriglyceridemiaPreliminary or mixed
EPA and DHA lower triglycerides by about 15% in a review; cod liver oil was not singled out and supplies less EPA and DHA than purified products.
Documented risks and interactions (3)
- Risk: too much vitamin A. Long-term intake above 1.5 mg a day may weaken bones, and fish liver oil is high in vitamin A.
- Risk: too much vitamin D. Long-term overuse of vitamin D supplements can cause too much calcium in the blood, which may harm bones, kidneys and heart.
- Risk: avoid in pregnancy. The NHS advises avoiding fish liver oil supplements when pregnant or trying for a baby unless a GP advises otherwise.
What cod liver oil is
Cod liver oil is a fish liver oil. NCCIH says fish liver oil supplements such as cod liver oil contain EPA and DHA, and also vitamins A and D in amounts that vary from product to product, and that vitamins A and D can be harmful in excessive amounts. [5] Standard fish oil is made from fish flesh; see fish oil. The comparison is in fish oil vs cod liver oil, and the vitamin detail is in cod liver oil vitamin A and D content and pregnancy caution. Because amounts vary, we do not state a typical vitamin A or D amount per serving: read the Supplement Facts panel of the product.What the research shows
Evidence labels: established nutritional role (vitamins A and D as nutrients), limited (a single small trial), insufficient evidence.| Question | What the source found | Label |
|---|---|---|
| Omega-3 outcomes (heart, brain, eyes) | The large omega-3 reviews covered mostly fish oil or purified products. [6] We found no cod-liver-oil outcome trial for these in the sources we read: Proper evidence not found. | Insufficient evidence |
| Cholesterol | A single-blind placebo-controlled trial of 600 treatment-naive patients with raised cholesterol gave 415 mg cod liver oil a day plus 10 mg rosuvastatin; at day 30 total cholesterol and LDL were lower than with rosuvastatin alone. [7] | Limited: 30 days, single-blind, blood measures only |
| Vitamin D | See the NHS figures below and vitamin D. | Established nutritional role |
| Vitamin A | See the NHS figures below and vitamin A. | Established nutritional role |
Vitamin A and D: official UK figures
These are UK NHS figures. Other countries set different limits; see RDA, AI, DV and UL. Figures from the NIH Office of Dietary Supplements could not be verified because the site blocked our download.| Nutrient | Group | Figure | Source and year |
|---|---|---|---|
| Vitamin A (retinol equivalents) | Adults 19 to 64, men | 700 micrograms a day | NHS, page reviewed 2020 [8] |
| Vitamin A (retinol equivalents) | Adults 19 to 64, women | 600 micrograms a day | NHS, page reviewed 2020 [8] |
| Vitamin A, advice not to exceed | Adults, from food and supplements combined | 1.5 mg (1,500 micrograms) a day | NHS, page reviewed 2020 [8] |
| Vitamin D, supplement | Adults and children from age 1 | 10 micrograms a day is enough for most people | NHS, page reviewed 2020 [9] |
| Vitamin D, not to exceed | Adults, including pregnant and breastfeeding women, and children aged 11 to 17 | 100 micrograms (4,000 IU) a day | NHS, page reviewed 2020 [9] |
| Vitamin D, not to exceed | Children aged 1 to 10 | 50 micrograms (2,000 IU) a day | NHS, page reviewed 2020 [9] |
The NHS says more than an average of 1.5 mg of vitamin A a day over many years may affect bones and make fractures more likely when older, and lists fish liver oil among supplements high in vitamin A. [8] It says that if you eat liver or liver products every week you should not take supplements containing vitamin A, including fish liver oil. [8] Cod liver oil taken with a multivitamin or other products can add up; see amounts and duplicate ingredients.
Frequently asked questions
Is cod liver oil the same as fish oil?
No. It is a liver oil that also supplies vitamins A and D in amounts that vary by product. [5]
Can I take cod liver oil when pregnant?
The NHS advises avoiding fish liver oil supplements in pregnancy unless a GP advises otherwise. [1]
How much vitamin A is too much?
The NHS advises against more than 1.5 mg (1,500 micrograms) a day from food and supplements combined. [8] This is UK advice for adults.
Does cod liver oil lower cholesterol?
One 30-day single-blind trial of cod liver oil plus rosuvastatin found lower total cholesterol and LDL than rosuvastatin alone. [7] This is limited evidence.
Does cod liver oil help the heart or brain?
Proper evidence not found for cod liver oil specifically. The large reviews covered other products. [6]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Quick safety points first
- Pregnancy. The NHS says that unless your GP advises otherwise, you should avoid fish liver oil supplements when pregnant or trying for a baby, because they are high in vitamin A (retinol), which can be harmful to an unborn baby. [1]
- Too much vitamin A. MedlinePlus says taking too much vitamin A can cause serious illness, and babies and children can become sick after smaller doses than adults. [2] If a child or anyone has swallowed a large amount of a vitamin product, call Poison Help at 1-800-222-1222 in the US (other countries: poison help by country); call 911 if the person collapses or cannot breathe.
- Blood thinners and surgery. Omega-3 prescription labels say omega-3 acids may prolong bleeding time. [3] Tell your providers about supplements well before surgery. [4] Do not stop a prescribed medicine yourself; ask the prescriber or a pharmacist.
Side effects and special groups
- Omega-3 side effects (taste, bad breath, heartburn, nausea, diarrhea) can occur. [5]
- Children: MedlinePlus says children are more sensitive to vitamin A. [2] We found no agency source on cod liver oil amounts for children (Proper evidence not found). Ask a pediatrician or pharmacist.
- Kidney or liver conditions, older adults: no cod-liver-oil-specific advice in the sources we read. Ask a clinician.
- Product quality and label accuracy vary; see quality testing and certifications and medication interactions.
References
- NHS, Fish and shellfish. Read 2026-10-22.
- MedlinePlus, Vitamin A. Read 2026-10-22.
- FDA-approved prescribing information, omega-3-acid ethyl esters capsules (generic prescription product), DailyMed, revised 5/2026. Read 2026-10-22.
- NCCIH, Using Dietary Supplements Wisely. Read 2026-10-22.
- NCCIH, Omega-3 Supplements: What You Need To Know. Read 2026-10-22.
- Abdelhamid AS et al., Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease, Cochrane Database Syst Rev 2020. Read 2026-10-22.
- Role of Cod Liver Oil in Reducing Elevated Lipid Parameters, Cureus 2021. Read 2026-10-22.
- NHS, Vitamin A. Read 2026-10-22.
- NHS, Vitamin D. Read 2026-10-22.