What Are the Side Effects of Too Many Vitamins?

Quick Take

While vitamins are essential, there are side effects of too many vitamins. It is important to be able to recognize how and when a person is taking excessive amounts of vitamins as well as what to do about it.

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According to Medscape, 44 percent of Americans take dietary supplements and vitamins every day. About 84 percent of those individuals believe that taking these is completely safe. This means that the majority of people are probably unaware that it is possible to overdose on vitamins.

Water-Soluble Versus Fat-Soluble

The body does not store water-soluble vitamins. When they are ingested, they dissolve in water and then enter the bloodstream. The body retains what is necessary and excretes the rest via the urine. All of the B vitamins and vitamin C are water-soluble vitamins.

The body stores fat-soluble vitamins. They dissolve in fat when they are ingested. As long as a person is healthy and has a healthy digestive system, the body uses what it needs of the fat-soluble vitamins - as it needs them - and keeps the rest stored for the future. Vitamins A, D, E and K are fat-soluble vitamins.

Side Effects and Toxicity

General side effects of toxicity include nausea, diarrhea, rash and vomiting. These can occur when the person’s overdose is acute or chronic. In some cases, what makes up the vitamin, such as the binders and other additives, will cause someone to experience a reaction.

The side effects of too many vitamins depend on which vitamin is responsible for the toxicity.

Acute vitamin A toxicity may cause headache, anorexia, vomiting, drowsiness, seizures, photophobia, nausea, abdominal pain, irritability and desquamation. Patients may also experience skin, neurologic and muscular effects.

Acute vitamin E toxicity may cause nausea, abdominal cramps, headache, easy bleeding and bruising, diplopia, creatinuria, gastric distress, diarrhea, fatigue, inhibition of platelet aggregation, and muscle weakness.

Acute vitamin D toxicity may cause muscle weakness, headache, irritability, vomiting, apathy, anorexia, nausea and bone pain. Chronic toxicity may cause acute symptoms such as anorexia, polydipsia, backache, hypercalcemia, constipation, abdominal cramps, polyuria and hyperlipidemia.

Folate or vitamin B-1, 2 and 12 single acute toxicity is rare. Vitamin B-1 toxicity may cause tachycardia, cardiac dysrhythmias, anaphylaxis, weakness, hypotension, headache, vasodilation and convulsions.

Vitamin B-3 acute toxicity may cause flushing, wheezing, headache, diarrhea, pruritus, vasodilation, vomiting and increased intracranial blood flow. Chronic toxicity may cause jaundice, liver toxicity signs, abnormal liver function tests, and (rarely) acanthosis nigricans.

Vitamin B-6 acute toxicity may cause tachypnea, burning pains, ataxia, paralysis, paresthesias, clumsiness, perioral numbness, and other sensory neuropathies.

Vitamin C toxicity may cause renal colic, nausea, and rebound scurvy.

Knowing the difference between water-soluble and fat-soluble vitamins is critical. In a nutshell, the body stores fat-soluble vitamins rather than water-soluble ones so individuals need to consume more water-soluble vitamins. While it is easier to experience vitamin toxicity with fat-soluble vitamins, it is possible to take too many water-soluble vitamins if one is not careful. It’s best to consult with a healthcare professional or licensed nutritionist to understand how much of a specific vitamin one should consume so toxicity can be avoided.