How Long Does It Take for Fish Oil to Work?

There are a lot of supplements on the market, and one of the most popular is fish oil. Fish oil is the primary source of two omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), according to the Mayo Clinic.

Omega-3s are linked to reduced inflammation and a lower risk of heart disease, plus improved cholesterol levels and arthritis symptoms. The amount of time it takes for fish oil supplements to take effect depends on a few factors.

Fish oil supplements play the long game — there's no instant gratification, but you can achieve long-term benefits with time.

You shouldn't expect instant results with fish oil supplements, but your body should attain optimal levels within at least three months, says Jonathan Golberg, MD, a New York-based general practitioner.

Once you begin taking fish oil consistently, the omega-3 levels in your body will increase, but it still might take up to six months to see a noticeable difference, per the University of Wisconsin School of Medicine and Public Health.

Translation: It might take between three and six months for fish oil to work.

"It is a supplement you can take lifelong, but I'd suggest getting bloodwork done to really see what's going on," Dr. Golberg says. "In order to see benefits, I'd encourage getting cholesterol testing."

Effectiveness also depends on the starting point of your overall health. If you are deficient in omega-3s, the severity of the deficiency will influence how soon levels get back to normal.

The type of fish oil, or chemical form, also makes a difference. Blood levels of EPA and DHA (omega-3s) increased more in people taking krill oil compared to those who took other forms of fish oil, per an August 2011 study in ‌Lipids in Health and Disease.‌

If you don't get enough omega-3s from your regular diet, supplementing with fish oil can help support heart, brain and eye health, according to the Cleveland Clinic. While fish oil can be helpful, it doesn't replace the need for a nutritious diet.

"Fish oil supplements do require consistency, but there can be big benefits when it comes to brain function and preventing chronic illnesses like heart disease and high blood pressure," says Alexa Topakas, RDN.

The American Heart Association recommends eating two 3-ounce servings of fish each week.

Healthy sources of omega-3s include:

• Salmon
• Mackerel
• Trout
• Sardines
• Canned tuna
• Anchovies

Taking too much fish oil (aka at least 900 milligrams of EPA plus 600 milligrams per day of DHA for several weeks) can cause negative side effects such as a weakened immune system, per the National Institutes of Health.

If you take medications to treat diabetes or if you take blood thinners, fish oil supplements are not recommended until you talk to your doctor.

"Certain medications can have bad interactions with fish oil, even if it's a low dosage," Dr. Golberg says. "That's why it's important to talk with your doctor before starting any supplement routine. [Taking a supplement] might not be necessary."

Minor side effects can include gas, bloating and diarrhea. A solution to mild side effects is taking smaller doses during the day or using time-release supplements.

If fish oil supplements are something you plan to incorporate into your daily routine, what's most important is that you take them consistently.

"The timing of the day for those medications shouldn't matter," Dr. Golberg says. Doctors agree it can be taken at any time of day, but what may have an affect is whether or not the supplement is taken with food.

A March 2019 study in ‌Current Opinion in Clinical Nutrition and Metabolic Care‌ suggests omega-3s are better absorbed when taken with a meal that includes a source of dietary fat (such as avocado, nuts or nut butters, seeds or olive oil). If taken on an empty stomach, there's a chance the body won't absorb the omega-3s as well.

"Whether it's taken in the morning with breakfast or at night after dinner, I do encourage clients to have a little something on their stomach in order to get the most out of it," Topakas says.