Cod Liver Oil

Gadus morhua liver oil · fish liver oil

Snapshot

Indications	Contraindications
Rickets prevention¹ Vitamin D status² Rheumatoid arthritis³ Gestational diabetes (cod-liver oil)⁴ Maternal-infant DHA supply⁵ Exercise-induced inflammation⁶	Vitamin A toxicity⁷ Unexplained hypercalcemia⁷

Cod liver oil, from the liver of Gadus morhua, supplies vitamin D and preformed vitamin A together with the long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Vitamin D promotes intestinal calcium and phosphate absorption, and in a historical open-label trial cod liver oil prevented rickets in infants. Habitual users in northern Norway show higher vitamin D status. Other uses follow from the omega-3 content, including metabolic support in gestational diabetes. In one trial, glucose and lipids were lower after 12 to 16 weeks, but there was no difference at four weeks⁴.

The evidence is mixed. A large quadruple-blind trial in Norwegian adults found no reduction in acute respiratory infections⁸. In gestational diabetes, a randomized trial found no difference in primary glycemic outcomes, but secondary markers were lower in the supplemented group⁴. A prospective cohort found no effect of cod liver oil supplements on type 2 diabetes risk⁹. A 2022 analysis of marine-sourced supplements detected lipid-soluble arsenic compounds in unprocessed fish liver oils¹⁰. Products listing cod liver oil are common, sold mainly as softgels and liquids; see Form comparison.

Last updated October 15, 2026. Read how we make monographs.

In the full monograph

62 sources, 47 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources