Is there any need to take fish oil supplements with food? Or do they work just as well if they are taken on an empty stomach?
Fish oil is a fat. Supplements relating to fat and fat solubility have usually one thing in common: the fat digestion and nutrient extraction is usually improved when these fats are consumed like in a normal meal. But this is really just a general rule of thumb. Since real meals containing these are probably better anyway.
But more important are the possible immediate side-effects:
Fish oil is likely safe for most people when taken by mouth in low doses (3 grams or less per day). There are some safety concerns when fish oil is taken in high doses. Taking more than 3 grams per day might keep blood from clotting and can increase the chance of bleeding.
High doses of fish oil might also reduce the immune system's activity, reducing the body's ability to fight infection. This is a special concern for people taking medications to reduce their immune system's activity (organ transplant patients, for example) and the elderly.
Only take high doses of fish oil while under medical supervision.
Fish oil can cause side effects including belching, bad breath, heartburn, nausea, loose stools, rash, and nosebleeds. Taking fish oil supplements with meals or freezing them can often decrease these side effects. … (emphasis in this paragraph added)