Dear Kosher Spirit,
Do cod fish oil capsules need a hechsher, even if they are made
with vegetarian capsules?

The OK responds:

All fish oil capsules, even those made with vegetarian capsules, require a hechsher when they are taken as a nutritional supplement. Many companies include oil from non-kosher fish, so supervision is definitely needed. (Halacha requires a mashgiach temidi for fish productions, unless the skin is left on the fish.) In addition, the processing methods need to be verified to ensure that the equipment is not also used for non-kosher products.

If a doctor prescribes a fish oil capsule it falls into a different category and the patient should discuss the specific fish oil capsule and his health requirements with his Rav. If necessary, the patient should have his Rav speak to the doctor to make sure all the information is taken into consideration.