Cod liver oil comes from the liver of Atlantic cod fish and contains omega-3 fatty acids, vitamin A, and vitamin D
Cod liver oil is a supplement made by processing the livers of Atlantic cod. Unlike other fish oils that come from the flesh of the fish, cod liver oil is extracted specifically from the liver, which concentrates certain nutrients. The oil is typically sold in liquid form or as soft gel capsules.
The supplement has been used for centuries—particularly in Scandinavian and Northern European cultures where cod fishing was common. People took it historically because it was a reliable source of nutrients that were otherwise hard to get in winter months. Today, people take cod liver oil because it contains three compounds that research has examined: omega-3 fatty acids (EPA and DHA), vitamin A, and vitamin D.
Key Takeaways
- Cod liver oil contains omega-3 fatty acids, vitamin A, and vitamin D in one supplement, which is why some people prefer it to plain fish oil.
- The vitamin A content in cod liver oil is high enough that taking too much over time can build up in your body and cause problems, unlike water-soluble vitamins.
- Typical doses range from 1 to 3 grams per day, but the right amount depends on why you are taking it and what your doctor recommends.
- Cod liver oil can thin blood slightly and may interact with blood thinners or certain other medications, so telling your doctor you take it matters.
The three main compounds in cod liver oil and what research shows
Omega-3 fatty acids (EPA and DHA) are the compounds most people associate with fish oil. Research has examined whether omega-3s support heart health, brain function, and inflammation in the body. Some studies suggest omega-3s may help with heart rhythm and cholesterol levels, though the evidence is mixed and ongoing.
Vitamin A supports eye health, immune function, and skin. Cod liver oil contains a significant amount—often 4,500 to 10,000 IU per teaspoon, depending on the brand. This is important because vitamin A is fat-soluble, meaning your body stores it rather than excreting excess amounts like it does with water-soluble vitamins. Taking too much over months or years can cause buildup.
Vitamin D helps your body absorb calcium and supports bone health and immune function. Cod liver oil typically contains 400 to 1,000 IU per teaspoon. Many people in northern climates or those who spend little time in sunlight take vitamin D supplements, and cod liver oil is one way to get it alongside omega-3s.
How much cod liver oil people typically take
Standard doses range from 1 to 3 grams per day, though some people take more. The right dose depends on why you are taking it and what your doctor or healthcare provider recommends. A typical soft gel capsule contains 1 gram, so taking one to three capsules daily is common.
Because vitamin A accumulates in your body, it is worth checking the label and knowing your total vitamin A intake from all sources—including multivitamins, fortified foods, and other supplements. The upper safe limit for vitamin A is generally considered 10,000 IU per day for adults, though some experts suggest lower limits for long-term use. If you are pregnant or planning to become pregnant, vitamin A intake matters more, so discussing cod liver oil with your doctor is especially important.
Who might consider taking cod liver oil
People often turn to cod liver oil for several reasons. Some take it because they want omega-3s but prefer a single supplement that also includes vitamin D. Others specifically want the vitamin D, especially if they live in a climate with limited sunlight or spend most of their time indoors. Some people take it because they have read about omega-3s and heart or brain health and want to explore that option.
People with certain diets may find cod liver oil useful—for example, those who eat little fish or fortified dairy may have lower intakes of vitamin D and omega-3s. However, if you already take a multivitamin, a separate vitamin D supplement, or eat fatty fish regularly, adding cod liver oil might mean getting more of these nutrients than you intend.
Possible side effects and interactions
Cod liver oil is generally well-tolerated, but some people experience mild side effects. The most common is a fishy aftertaste or burping that tastes like fish. Taking the capsule with food or freezing it before swallowing can reduce this. Some people report mild digestive upset, nausea, or loose stools, especially when starting or taking higher doses.
Cod liver oil can thin blood slightly, which matters if you take blood thinners like warfarin or clopidogrel, or if you take aspirin regularly for heart health. The effect is usually small, but your doctor should know you are taking it. If you are scheduled for surgery, mention cod liver oil to your surgical team, as they may ask you to stop it a week or two before the procedure.
Vitamin A can interact with certain medications, including some acne treatments and retinoid creams. If you take any prescription medications, checking with your doctor or pharmacist about cod liver oil is a straightforward step.
Cod liver oil versus other fish oils and vitamin D supplements
The main difference between cod liver oil and regular fish oil is that cod liver oil includes vitamin A and D, while standard fish oil contains only omega-3s. If you want omega-3s alone, fish oil is simpler. If you want omega-3s plus vitamin D, cod liver oil combines them. However, if you want to control each nutrient separately—taking a specific dose of vitamin D and a specific dose of omega-3s—buying them separately gives you more flexibility.
Some people take cod liver oil specifically for the vitamin D and accept the omega-3s as a bonus. Others take a vitamin D supplement and fish oil separately to dial in their doses. Neither approach is inherently better; it depends on your goals and what your doctor recommends. If you are already taking a multivitamin with vitamin A and D, adding cod liver oil could push your intake too high, so checking labels matters.
How to choose a cod liver oil product
Cod liver oil products vary in strength and form. Liquid versions typically contain more omega-3s per serving than capsules, but capsules are easier to take and have less fishy taste. Labels should list the amount of EPA, DHA, vitamin A, and vitamin D per serving so you can compare products and track your total intake.
Third-party testing organizations like USP, NSF, or ConsumerLab test some supplements to verify that the label matches what is inside the bottle and that contaminants like mercury are within safe limits. While not every product is tested, looking for a third-party seal can give you confidence. Refrigerating liquid cod liver oil after opening helps preserve it, and checking the expiration date matters because the omega-3s can degrade over time.
Frequently Asked Questions
Is cod liver oil safe to take every day?
Yes, for most adults taking standard doses (1 to 3 grams daily). The main concern is vitamin A buildup over time, so knowing your total vitamin A intake from all sources matters. If you are pregnant, planning pregnancy, or have liver disease, discuss it with your doctor first.
Can I take cod liver oil if I eat fish regularly?
You can, but you may be getting more omega-3s and vitamin D than you realize. Fatty fish like salmon and mackerel contain significant omega-3s, and some fish is fortified with vitamin D. Adding cod liver oil means adding more of these nutrients, which is fine for most people but worth being aware of.
Does cod liver oil really help with joint pain or arthritis?
Some research suggests omega-3s may help reduce inflammation and joint pain in people with rheumatoid arthritis, though the evidence is modest. For osteoarthritis, the evidence is weaker. If you are considering it for joint pain, discussing it with your doctor helps you decide whether it is worth trying for your situation.
What is the difference between fermented and regular cod liver oil?
Fermented cod liver oil is processed differently and some people claim it is more bioavailable or has additional benefits. The scientific evidence for these claims is limited. Both regular and fermented versions contain omega-3s, vitamin A, and vitamin D, so the choice often comes down to personal preference and price.
Can children take cod liver oil?
Yes, and it was historically a common children's supplement in Northern Europe. However, vitamin A dosing matters more for children because their bodies are smaller. If you are considering cod liver oil for a child, checking with your pediatrician about the right dose is important, especially if the child takes other supplements or a multivitamin.