Hello!

Thank you for the query.

Niacin is present in many foods so its supplementation should not cause nausea. However if your husband finds that after a niacin his nausea starts, he should stop taking it and see if this will help.

Nausea can have many reasons. Quite common reason is peptic ulcer or stomach inflammation. With this conditions, upper middle abdominal pain, chest burning can be present. Stomach problem is more possible if your husband takes a lot of pain killers.

Gallstones can be also a reason of nausea. Stones are invisible in abdominal CT. Upper right abdominal pain radiating to the back can be present. The pain and nausea is usually triggered by fatty foods, spicy foods or alcohol.

If there is also problem with stool like diarrhea or constipation, bloated abdomen, blood in stool, also large intestine issues (like partial bowels obstruction) or infection should be considered.

Nausea can be also caused by blood pressure drop, low blood sugar level, XXXXXXX ear issues (dizziness should be present), increased pressure in the skull (headache should be present, pupils can be uneven).

I suggest you to have some more diagnostics. Abdominal ultrasound (to rule out gallstones) and gastroscopy should be done at first. Blood sugar level and blood pressure should be also checked. In case of possible large intestine problems, stool tests or colonoscopy should be done.

If nothing will be found, your husband should visit neurologist and laryngologist.

Hope this will help. Feel free to ask further questions.
Regards.

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CT is not a test for stomach diagnostic. Peptic ulcer or an inflammation will be completely invisible in this test. Even some stomach cancers can be invisible in this test.
Gallstones wont show up in the CT as well. CT is a method based on X-rays. Most of the stones are invisible in X-rays.
So please follow mentioned before steps.

Hope this will help.
Regards.

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