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Yes, It's Possible to Overdose on Vitamins. Here's How to Avoid It

It's possible to take too many vitamins, leading to dangerous side-effects. Learn how to recognize vitamin overdosing and avoid it.

Bunch of different vitamins on a flat surface against a coral-colored background
Daniel Grizelj/Getty Images

You've likely seen the advice about which vitamins can help us achieve certain health goals. For instance, there are vitamins to boost your energy and others that aid in hair growth. Since vitamins are so good for us, you might even assume that more is better. But with certain vitamins, there can be too much of a good thing. Some vitamins can build up in your system and lead to unwanted side effects like nausea and headaches. Read on to learn how to tell if you're overdosing on vitamins, including common side effects for popular vitamins. 

Are you taking too many vitamins? 

Is taking too many vitamins bad? Some people also ask questions like: Can you take too much magnesium? Or can you take too much biotin? The key fact is that vitamins can be either water-soluble or fat-soluble. Water-soluble vitamins dissolve in water. This means that they can dissolve safely and pass out of your system if you take too many or the body does not need them. Fat-soluble vitamins do not dissolve in water. With time, too many of these fat-soluble vitamins build up in your body because they can be easily absorbed into your body's tissue, which can lead to toxicity.

Getting too many vitamins through our diets is unlikely to be harmful. Most food has relatively low amounts of vitamins. For instance, a 100-gram serving of eggs has 540 international units (IU) of vitamin A. However, men can have 3,000 IU daily (or 900 mcg RAE) and women can have 2,333 IU per day (or 700 mcg RAE), according to the Harvard T.H. Chan School of Public Health. Where vitamin dosing can get dangerous is when we start popping the highly concentrated supplements that may be delivering hundreds or even thousands of IUs per day, depending on how many individual vitamin supplements or what type of multivitamin we take. 

Potential side effects to watch out for 

Below is a list of popular vitamins. Read on to learn about which side effects can come from consuming too much of each vitamin.

Vitamin C

For decades, vitamin C has been touted as a way to prevent or cure colds. It might be easy to assume taking megadoses of it might even prevent illness. However, you can get too much vitamin C. While water-soluble, Mayo Clinic lists the side effects of vitamin C overdose as:

  • Vomiting
  • Diarrhea
  • Nausea
  • Heartburn
  • Stomach cramps
  • Headache 

Vitamin B3 

Also called niacin, the side effects of B3 overdose can include:

  • Itching 
  • Rapid heartbeat
  • Nausea and vomiting
  • Severe skin flushing with dizziness 
  • Abdominal pain 
  • Diarrhea 
  • Gout 

Vitamin B6 

Vitamin B6 may be also called pyridoxine. Its overdose side effects may be:

  • Having a lack of muscle control or coordination 
  • Heartburn
  • Nausea
  • Sensitivity to sunlight
  • Painful skin lesions
  • Numbness
  • Less ability to sense pain or extreme temperature 

Vitamin B9 

This vitamin is also called folate or folic acid. Excess folic acid is excreted in the urine, according to the Mayo Clinic. However, high folate intake might mask vitamin B12 deficiency until the neurological effects are permanent. Sometimes doctors prescribe taking both B12 and folic acid supplements together.

However, other side effects of regular oral use may include:

  • Nausea
  • Bad taste
  • Loss of appetite
  • Confusion 
  • Sleep pattern disturbance 
  • Irritability

Vitamin A 

Many people like supplementing with Vitamin A, since it's important for vision, cell division, immunity and growth. It also has natural antioxidant properties, so it may have cell-protecting attributes. However, it's fat-soluble so it can lead to issues with toxicity.

The Mayo Clinic says that a single large dose of over 200,000 IU may cause:

  • Vertigo 
  • Vomiting 
  • Nausea
  • Blurry Vision 
  • Over 10,000 IU per day might cause:
  • Liver damage
  • Bone thinning
  • Diarrhea
  • Nausea
  • Skin irritation
  • Bone or joint pain
  • Birth defects 
  • Headache 

Vitamin D 

Vitamin D toxicity usually comes from large doses of supplements, not exposure from the diet or sunlight, according to the Mayo Clinic. If you have vitamin D toxicity, also known as hypervitaminosis D, you may experience:

  • Nausea 
  • Vomiting 
  • Weakness
  • Frequent urination 
  • Bone pain
  • Kidney issues, like having calcium stones 

These side effects come from overdoses of Vitamin D causing a buildup of calcium in the bloodstream. 

Vitamin E 

Vitamin E is another popular vitamin with antioxidant properties, so it's easy to assume more means better. Vitamin E supplementation can come with the following side effects, and higher doses can increase the risk of these side effects:

  • Weakness
  • Headache
  • Fatigue
  • Blurred vision
  • Rash
  • Gonadal dysfunction
  • Increased concentration of creatine in urine
  • Nausea
  • Diarrhea
  • Intestinal cramps 

How to take vitamins safely 

Make sure that you are staying within the daily recommended doses for each vitamin supplement that you take. Factor in how much of the vitamin you get from daily food sources. The recommended daily intake for each major vitamin is:

Vitamin A

  • Men: 900 mcg
  • Women: 700 mcg

Vitamin B1

  • Men: 1.2 mg
  • Women: 1.1 mg

Vitamin B2

  • Men: 1.3 mg
  • Women: 1.1 mg

Vitamin B3

  • Men: 16 mg NE (niacin equivalents) 
  • Women: 14 mg NE

Vitamin B5

  • Men: 5 mg
  • Women: 5 mg

Vitamin B6 

  • Men: 1.3 mg
  • Women: 1.3 mg

Vitamin B7

  • Men: 30 mcg
  • Women: 30 mcg

Vitamin B9 

  • Men: 400 mcg DFE (dietary folate equivalents) 
  • Women: 400 mcg DFE

Vitamin B12

  • Men: 2.4 mcg
  • Women: 2.4 mcg

Vitamin C

  • Men: 90 mg
  • Women: 75 mg

Vitamin D

  • Men: 600 IU
  • Women: 600 IU

Vitamin E

  • Men: 15 mg
  • Women: 15 mg

Vitamin K

  • Men: 120 mcg
  • Women: 90 mcg

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.