Can fish oil, fiber, semaglutide, amphetamine/dextroamphetamine, magnesium, Vitamin D, and L-citrulline cause gastrointestinal symptoms such as diarrhea and nausea?

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Last updated: February 19, 2025View editorial policy

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From the Guidelines

It is likely that one or more of the supplements or medications you are taking could be causing diarrhea and nausea.

Potential Causes of Gastrointestinal Symptoms

Out of the listed substances, fiber is known to potentially cause gastrointestinal side effects, including diarrhea and nausea, especially when taken in high doses 1.

  • Semaglutide, a glucagon-like peptide-1 receptor agonist, may also be associated with nausea, vomiting, diarrhea, or constipation and should be titrated slowly 1.
  • Fish oil, magnesium, and L-citrulline are also known to potentially cause gastrointestinal side effects, including diarrhea and nausea, especially when taken in high doses.
  • Amphetamine/dextroamphetamine can also cause stomach upset in some individuals.
  • Vitamin D is less likely to cause immediate gastrointestinal side effects but can cause nausea if taken in excess. To minimize potential side effects, consider reducing the dose of fish oil, magnesium, and L-citrulline, and ensure you are drinking plenty of water and gradually increasing your fiber intake. If symptoms persist, consult a healthcare professional for personalized advice.

From the FDA Drug Label

Gastrointestinal: Dryness of the mouth, unpleasant taste, diarrhea, constipation, other gastrointestinal disturbances. OZEMPIC causes a delay of gastric emptying, and thereby has the potential to impact the absorption of concomitantly administered oral medications.

The amphetamine/dextroamphetamine can cause gastrointestinal symptoms such as diarrhea. The semaglutide may cause a delay in gastric emptying, which could potentially impact the absorption of other medications, but it does not directly state that it causes gastrointestinal symptoms such as diarrhea and nausea. There is no information in the provided drug labels about fish oil, fiber, magnesium, Vitamin D, and L-citrulline that directly supports the answer to the question. 2 3

From the Research

Gastrointestinal Symptoms

The following substances have been studied for their potential to cause gastrointestinal symptoms such as diarrhea and nausea:

  • Magnesium: A study published in 1991 4 found that excessive ingestion of magnesium can cause chronic diarrhea in some individuals.
  • Vitamin C: Although not directly related to the question, a study published in 1983 5 mentioned that occasional individuals may experience diarrhea or mild nausea when taking supplemental vitamin C.
  • Lithium: A case report published in 2007 6 described a patient who experienced nausea and emesis after ingesting a lithium-containing dietary supplement.
  • Cinnamon: A case report published in 2015 7 described a patient who experienced abdominal pain, vomiting, and diarrhea after taking cinnamon supplements.
  • Polyphenols: A review published in 2023 8 discussed the potential harmful effects of polyphenols, including inhibition of digestive enzymes and interactions with drugs, which may lead to gastrointestinal symptoms.

Specific Substances

The following substances were mentioned in the question but have limited or no relevant evidence:

  • Fish oil: No relevant studies were found.
  • Fiber: No relevant studies were found.
  • Semaglutide: No relevant studies were found.
  • Amphetamine/dextroamphetamine: No relevant studies were found.
  • L-citrulline: No relevant studies were found.
  • Vitamin D: No relevant studies were found.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Diagnosis of magnesium-induced diarrhea.

The New England journal of medicine, 1991

Research

Lithium toxicity from an Internet dietary supplement.

Journal of medical toxicology : official journal of the American College of Medical Toxicology, 2007

Research

Do cinnamon supplements cause acute hepatitis?

The American journal of case reports, 2015

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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