Vitamin Overdose and Toxicity

Scientific studies showed that vitamin and mineral supplementation may be beneficial to a person’s health. However, the harmful effects of vitamins often receive little attention(1).

For example, high doses of vitamin C may put people at risk of developing kidney stones(2). To diagnose the condition and support its treatment, doctors use advanced medical imaging procedures, like computed tomography (CT) or X-ray.

Experts have also noted the importance of looking for non-toxic vitamin alternatives that promote health without any adverse effects. To avoid the harmful effects of vitamins, some people opt for natural solutions to boost the immune system.

Water-Soluble vs. Fat-Soluble Vitamins

Vitamins are divided into two categories: fat-soluble vitamins and water-soluble vitamins(3).

Water-Soluble Vitamins

Water-soluble vitamins are compounds not stored by the human body. These compounds, including vitamins B and C, are excreted through urine(4).

Water-soluble vitamins are less likely to cause side effects even in high doses than fat-soluble compounds.

However, high doses of water-soluble vitamins may still trigger the onset of harmful conditions in the body.

For example, niacin or vitamin B3 may cause liver damage if administered in high doses(5). Additionally, taking high doses of vitamin B6 may lead to potential nerve damage over time(6).

Other water-soluble vitamins include thiamin, riboflavin, and folacin(7).

Fat-Soluble Vitamins

Fat-soluble vitamins are compounds that do not dissolve in water and are stored in the body’s tissues(8). Fat-soluble vitamins include vitamins A, D, and E(9).

Although uncommon, taking these vitamins in high doses may lead to harmful side effects(10).

Side Effects of Vitamin Overdose

Vitamins are generally safe to consume on a daily basis. However, taking high doses of these supplements may trigger adverse side effects.

Although rare, there have been recorded cases of death associated with vitamin toxicity.

Complications arising from vitamin overdose vary depending on the compound administered.

Fat-Soluble Vitamins

Vitamin A

Hypervitaminosis A (vitamin A toxicity) may occur from consuming high amounts of vitamin A supplements.

Data from the Mayo Clinic show that high doses of vitamin A may cause(11):

  • Diarrhea
  • Joint pain
  • Headache
  • Nausea
  • Skin irritation
  • Liver damage
  • Birth defects

Vitamin A overdose may also trigger increased intracranial pressure, coma, and even death(12).

A study on hypervitaminosis A was conducted on a patient with kidney failure.

Results showed that one large dose of more than 200mg of vitamin A, which is over ten times the recommended daily dose, may lead to serious complications. These complications include higher spinal fluid pressure, coma, and fatal organ damage(13).

Vitamin D

Side effects of vitamin D overdose include weight loss, irregular heartbeat, and appetite loss. Vitamin D overdose may also boost blood calcium levels, which may lead to organ damage(14).

Additionally, taking over 50,000 IU of vitamin D daily over long periods may increase calcium levels in the blood. This condition, called hypercalcemia, is potentially fatal(15).

Vitamin E

Excessive vitamin E intake may affect the body’s blood clotting process, cause hemorrhages, and even trigger a hemorrhagic stroke(16).

Water-Soluble Vitamins

Vitamin C or Ascorbic Acid

Adverse effects of vitamin C overdose include migraine headaches, nausea or vomiting, flushing, and dizziness(17).

Vitamin C overdose may also cause tissue damage and fatal heart conditions in patients with hemochromatosis, a disorder caused by iron buildup in the body(18).

Vitamin B3 or Niacin

High niacin doses may cause abdominal pain, high blood pressure, impaired vision, and liver damage. Nicotinic acid, a form of niacin, may cause severe skin flushing, dizziness, and nausea(19).

Vitamin B6 or Pyridoxine

Long-term intake of vitamin B6 in high doses may cause skin lesions, severe neurological impairment, heartburn, sensitivity to light, and nausea(20).

Vitamin B9 or Folate

Overconsumption of folate or folic acid may affect cognitive function, leading to mental decline.

High folate levels may also impair immune system response and hinder the detection of a potentially severe vitamin B12 deficiency(21).

Taking Vitamin and Mineral Supplements Safely

The dosage of vitamin and mineral supplements depends on several factors, including the person’s age, medical conditions, genetic disorders, and diet.

Although most manufacturers provide dosing guidelines for supplements, dosage needs vary from person to person.

It is not recommended to administer more than the tolerable upper intake levels set for vitamin and mineral supplements. Taking high doses may result in adverse effects and, in rare circumstances, even death.

It is important to seek medical advice before consuming vitamin and mineral supplements in high doses.

Doctors and other medical professionals can offer advice about safe and accurate dosing to avoid adverse effects.


  1. Wooltorton, E., Too much of a good thing? Toxic effects of vitamin and mineral supplements. Canadian Medical Association Journal, 169(1): 47–48.
  2. Massey, L., Safety of vitamin C. The American Journal of Clinical Nutrition.  August 2005, Page 488,
  3. Albahrani, A. & Greaves, R. (2016). Fat-Soluble Vitamins: Clinical Indications and Current Challenges for Chromatographic Measurement. The Clinical Biochemist Reviews,  37(1): 27–47.
  4. National Research Council (US) Committee on Diet and Health. Washington (DC): National Academies Press (US); 1989.
  5. Leung, K., Quezada, M., Chen, Z., Kanel, G., & Kaplowitz, N. (2018). Niacin‐Induced Anicteric Microvesicular Steatotic Acute Liver Failure. Hepatology Communications, 2(11): 1293–1298.
  6. Bacharach, R., Lowden, M., & Ahmed, A. (2017). Pyridoxine Toxicity Small Fiber Neuropathy With Dysautonomia: A Case Report. Journal of Clinical Neuromuscular Disease, 19(1):43-46.
  7. National Research Council (US) Committee on Diet and Health. Op cit.
  8. Lykstad, J. &  Sharma, S. (2020). StatPearls.
  9. A. Albahrani, et al. Op cit.
  10. Hamishehkar, H., Ranjdoost, F., Asgharian, P., Mahmoodpoor, A., & Sanaie, S. (2016). Vitamins, Are They Safe? Advanced Pharmaceutical Bulletin, 6(4): 467–477.
  11. Mayo Clinic. Vitamin A. Retrieved from
  12. National Institutes of Health, Office of Dietary Supplements. Vitamin A. Retrieved from
  13. Hammoud, D., Haddad, B., & Abdallah, J. (2014). Hypercalcaemia Secondary to Hypervitaminosis A in a Patient with Chronic Renal Failure. West Indian Medical Journal, 63(1): 105–108.
  14. National Institutes of Health, Office of Dietary Supplements. Vitamin D. Retrieved from
  15. Koul, P., Ahmad, S., Ahmad, F., Jan, R., Shah, S., & Khan, U. (2011). Vitamin D Toxicity in Adults: A Case Series from an Area with Endemic Hypovitaminosis D. Oman Medical Journal,  26(3): 201–204.
  16. National Institutes of Health, Office of Dietary Supplements. Vitamin E. Retrieved from
  17.  Abdullah, M., Jamil, R., & Attia, F. (2020). StatPearls. Vitamin C (Ascorbic Acid).
  18. Aronow, W. (2018). Management of cardiac hemochromatosis. Archives of Medical Science, 14(3): 560–568.
  19. National Institutes of Health, Office of Dietary Supplements. Niacin. Retrieved from
  20. National Institutes of Health, Office of Dietary Supplements. Vitamin B6. Retrieved from
  21. National Institutes of Health, Office of Dietary Supplements. Folate. Retrieved from

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