DHA Side Effects
Nausea, gas, and a fishy aftertaste are the most common side effects seen with DHA. Side effects of the supplement are generally minor, but it is possible to develop serious side effects (especially if you take higher doses of DHA). Side effects which may indicate that you should stop taking DHA include any signs of internal bleeding or allergic reactions.
Even though it is a "natural" product, DHA (docosahexaenoic acid) is not always free of side effects. For most people, these side effects are merely bothersome. However, DHA can sometimes cause serious side effects as well, especially when taken at higher dosages. Also, it is possible that DHA obtained from fish sources could contain heavy metals or other toxins, if it is not purified properly.
Many people experience nausea and gas when taking DHA supplements. Taking DHA with food may help prevent or lessen the nausea. If the DHA is derived from fish, you may also experience a fishy aftertaste. Again, taking it with food may help reduce this side effect.
Since DHA may have anticoagulant ("blood-thinning") effects, some people may notice that they bruise more easily. It may also take a little longer for a cut to stop bleeding. While this may be merely bothersome, it can become serious in some situations. However, some researchers believe that taking DHA alone (without EPA) may not actually have these anticoagulant effects. EPA (eicosapentaenoic acid) is a similar but different omega-3 fatty acid usually used in combination with DHA (in the form of fish oil).