Can You Take Too Many Vitamins? 4 Signs of Vitamin Overdose

Benedict Ang, CPT, PN1-NC
Published by Benedict Ang, CPT, PN1-NC | Staff Writer & Senior Coach
Last updated: June 21, 2024
FACT CHECKED by Dr. Kristy Dayanan, BS, MD
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Millions of people worldwide take vitamins as a part of their daily nutrition.

And it seems like everything is vitamin-enriched, from bottled water to orange juice and fortified foods.

This is great, and it may seem as if all your needs are covered, but you can quickly go overboard and cause a vitamin overdose.

With our resident dietitian, we came up with everything you need to know about taking too much vitamin and how it affects you.

You can check out also our list of tested and recommended multivitamins for men and women.

Quick Summary

  • Taking too many vitamin supplements over an extended period can result in organ failure, increased spinal fluid pressure, or even coma.
  • The early signs you have overdosed on your vitamins are difficulty sleeping, feeling irritable, and having nerve problems.
  • An estimated 3.2% of the U.S. adult population, as of 2013-2014, took supplements containing 100 mcg (4,000 IU) or more of Vitamin D, which is a high dose.
  • As a fitness professional, I recommend consulting a physician before taking supplements, especially in high doses, to ensure safe and effective use.

4 Signs You've Taken Too Many Vitamins

A sleep deprived person

Research is unclear on the long-term effects of slightly exceeding recommended vitamin supplement doses. However, there are subtle signs to watch for.

These mild symptoms of taking too many vitamins and minerals may include:

  • Difficulty sleeping
  • Difficulty concentrating
  • Nerve problems such as numbness or tingling
  • Feeling irritable

Of course, this depends on the specific vitamins you take too much of.

Moreover, the over-fortification of our foods should be a much bigger concern.

Food producers often fortify foods with vitamins and supplements like vitamin D and omega-3 fats. This can make it challenging to track daily vitamin intake, potentially leading to dietary imbalances.

Regarding maintaining a balanced diet, dietary supplements play a significant role. However, it is crucial to exercise caution and not exceed the recommended dosage.

Consuming excessive dietary supplements, including vitamins, can adversely affect your health.

"I have not seen someone off the street who was taking a toxic level of vitamin A or D -- those are very unusual. What I'm more likely to see is a person with a dosing level of supplements that's higher than optimal."

- David Katz, MD, Director of the Yale University Prevention Research Center in New Haven, CT

Potential Risks of Taking Too Many Vitamins

Different vitamins on yellow background

When consumed naturally through foods, vitamins and minerals don’t usually cause harm, even when consumed in large amounts.

However, when you take them in concentrated doses in the form of vitamin supplements, it’s easy to take too much and cause negative health outcomes.

For discussion purposes, we’ll divide the potential risks of too much vitamins based on whether they are water or fat-soluble.

There are 13 known vitamins which are divided into two groups:

  • Fat-soluble vitamins stored in our bodies' fat tissues. These are vitamins, A, D, E, K, which may accumulate in our body and cause toxicity and severe side effects in some rare cases.

Water-soluble vitamins are excreted through urine and aren't stored in our bodies.

These are vitamin C and all B vitamins. They're not likely to cause harm or severe side effects even if taken in high doses. But taking megadoses of this vitamin group can cause nerve and liver damage.

Possible Side Effects of Fat-Soluble Vitamins

A person holding a pill and a water on the other hand

As I mentioned, the four fat-soluble vitamins (Vitamin A, Vitamin D, Vitamin E, Vitamin K)

can accumulate in your body's tissues and cause some severe health issues when taken at high doses, especially if you take them over long periods.

Vitamin K is the only one from this group that has a low potential for toxicity.

Still, the remaining fat-soluble vitamins have the potential to cause some serious issues at high doses.

It's important to exercise caution and follow recommended dosage guidelines when consuming fat-soluble vitamins to maintain optimal health.

Some side effects caused by the overconsumption of fat-soluble vitamins include:

  • Vitamin A toxicity, known as hypervitaminosis A, can happen when eating too many vitamin-A-rich foods, but it's more often caused by taking too much vitamin supplement. Hypervitaminosis A symptoms include increased intracranial pressure, nausea, coma, and even death.
  • Vitamin D toxicity can lead to appetite and weight loss, as well as irregular heartbeat. Too much vitamin D supplements can also raise blood calcium levels, leading to organ damage [1].
  • Vitamin E can cause hemorrhages, interfere with blood clotting, and lead to hemorrhagic stroke.

Vitamin K has a low potential for toxicity, but it can still interact with certain medications, such as antibiotics and warfarin.

Possible Side Effects of Water-Soluble Vitamins

A water soluble vitamin inside a glass of water

Water-soluble vitamins (Vitamin C and B) may not be stored in our bodies, but taking too much of them can still cause adverse effects, some of which can be incredibly dangerous.

However, similarly to vitamin K, B1 (thiamine), B2 (riboflavin), B5 (pantothenic acid), B7 (biotin), and B12 (cobalamin) have low toxicity levels but can interact with medications and interfere with blood testing results.

But, when taken in high doses, these water-soluble vitamins can cause some adverse side effects:

  • Vitamin C has low toxicity, but high doses can cause gastrointestinal disturbances, such as nausea, vomiting, diarrhea, and cramps. You can also experience migraines if you take 6 grams of this vitamin daily.
  • Vitamin B3 (niacin) can lead to impaired vision, abdominal pain, high blood pressure, and liver damage if you consume it in doses of 1–3 grams a day.
  • Vitamin B6 (pyridoxine) can cause nausea, heartburn, sensitivity to light, skin lesions, and severe neurological symptoms if you take it in doses of 1–6 grams a day, according to a study from the National Institutes of Health [2].
  • Vitamin B9 (folate/folic acid) could potentially affect your mental function, negatively impact your immune system, and mask a potentially severe vitamin B12 deficiency if taken in high doses in the form of folic acid.

In my experience as a fitness professional, I've seen that individuals with specific health conditions can have more severe reactions to vitamin overdoses. It's crucial to monitor their intake closely.

Let’s take vitamin C as an example. Excessive amounts aren’t likely to cause toxicity in healthy people, but they might lead to tissue damage and fatal heart abnormalities in people with iron storage disorder.

Can Taking Too Many Vitamins Be Deadly?

A woman thinking about the risks of vitamins on her hand

Although it’s extremely rare to die from a vitamin overdose, there have been some cases of vitamin toxicity-related deaths.

To paint you a word picture —  hypervitaminosis A can be caused by a single 200mg dose of vitamin A. It can also be caused by chronic use of over ten times the recommended daily intake.

The toxic levels cause increased spinal fluid pressure, coma, and fatal organ damage.

Moreover, taking megadoses of vitamin D, over 50,000 IU a day, for long periods can cause high blood levels of calcium (hypercalcemia), which can lead to death.

Overdosing on other vitamins can also cause side effects that can lead to death.

Researchers have discovered that taking very high doses of over 5 grams of extended-release niacin can lead to a buildup of acid in body fluids and acute liver failure — both of which can have deadly outcomes.

Of course, an occasional high dosage of vitamins won't kill you; these examples are related to taking exceptionally high doses of vitamins.

Nevertheless, you should always be careful when taking any dietary supplement.

How To Safely Take Vitamins?

A woman looking at the vitamins on her hand

Vitamin bottles offer dosage recommendations, but individual needs vary. Consulting a doctor and prioritizing a balanced diet are key to meeting nutrient needs.

However, people take a daily multivitamin for many reasons, such as age, medical conditions, genetic disorders, and diet restrictions.

Even though some vitamins can cause serious side effects and health issues, they’re usually safe to take as long as you use them responsibly.

Your doctor may recommend taking more than the UL (tolerable upper intake levels) for specific nutrients to correct a deficiency in some circumstances.

FAQ

Can I Take Vitamins Daily?

Yes, you can take vitamins every day, but it's important to adhere to the recommended daily allowances and avoid exceeding them, as overconsumption can lead to overdose

What Are The Early Signs of Vitamin Overdose?

The early signs of vitamin overdose include nausea, diarrhea, skin rashes, and fatigue. Severe cases can lead to more serious symptoms like organ damage, so it's crucial to monitor your intake.


References:

  1. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
  2. https://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional/
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About The Author

Benedict Ang, CPT, PN1-NC
Staff Writer & Senior Coach
Benedict Ang, CPT, PN1-NC is an ex-National Soccer player turned MMA and Kickboxing champion, with ACE CPT and PN1-NC certifications. His advice is rooted in education and experience, ensuring that readers receive scientific and battle-tested insights. His mission is to empower his clients and readers to realize their potential and become the best versions of themselves.
Learn more about our editorial policy
Dr. Kristy June Dayanan, BS, MD is an author with a BS degree from University of the Philippines and an MD from University of Perpetual Help System. Her ability to simplify medical science complexities and dietary supplement jargon for the average reader makes her a valued medical fact checker and reviewer.
Learn more about our editorial policy
Dr. Harshi Dhingra, MBBS, MD is a published peer-reviewed author and renowned physician from India with over a decade of experience. With her MBBS from Bharati Vidyapeeth and an MD from Rajiv Gandhi University, she actively ensures the accuracy of online dietary supplement and medical information by reviewing and fact-checking health publications.
Learn more about our editorial policy

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