Can You Overdose on Vitamin D?

There is always ‘too much of a good thing’. This is why vitamin D, one of the most important vitamins in our body, needs to be taken in moderation. It is very rare to overdose on this vitamin, however. Most of the time, when it does happen, it is because children accidentally get hold of a supplement, the elderly take too much by accident, adults choose to take too much (more than 10,000 IU per day for a very long time), or if there is an industrial accident whereby very high quantities of the vitamin are added by mistake to fortified foods.

How Much Vitamin D Is Too Much?

All vitamins have what is called an RDA (recommended daily allowance or how much you should take per day), an IU (international unit, which measures how much you take) and the TUL (tolerable upper limit, which is how much you can take before you start noticing adverse symptoms). The official TUL for vitamin D is 2,000 IU per day. At the same time, however, the RDA is now also 2,000 IU and scientists now believe that the real TUL is much higher. In fact, many scientists claim that 2,000 IU is what children should take, which has come at the same time as ‘Call to Action’ letter that supported the idea that the TUL should actually be 10,000 IU.

There are now a number of studies that have shown that the current TUL levels are not based on facts. They state that studies have shown levels of 10,000 IU per day do not show adverse effects. They suggest that the real TUL is actually 40,000 IU, as this is sometimes prescribed to people who suffer from hypercalcemia.

There has, in fact, been a study in which 100,000 IU was given to pregnant women each day during their pregnancy. No adverse effects were noted in either mothers or babies. This could mean the TUL is actually as high as 100,000 IU.

Clearly, it isn’t easy to overdose on vitamin D. However, just because it’s hard doesn’t mean it is impossible. Almost all overdoses, as previously stated, are accidental to some degree. This means that there is always a chance that it may happen, so you must be aware of the symptoms as well.

Symptoms of Vitamin D Overdose

There are a number of very specific symptoms of vitamin D overdose, and some non-specific ones as well. They include:

• Marked thirst and dehydration
• Confusion
• Constipation
• Increased urination
• Nausea
• Heart rhythm abnormalities
• Vomiting
• Poor appetite
• Weight loss
• Weakness

However, all of these symptoms can also point to various other medical conditions. This is why it is important to seek medical advice and be tested for overdose. A test will look at whether there are high levels of calcium in the urine and serum. It will also measure the levels of 25-hydroxyvitamin D. If higher than 150 nanograms per milliliter, this would be cause for concern. Lastly, tests will measure whether the parathyroid hormone level can no longer be detected.

One thing to be aware of is that, if someone does overdose but continues to take vitamin D, there is a chance that this person will develop permanent kidney problems. In very rare cases, an overdose can be fatal, most notably because of abnormal electrolyte (blood salt) levels, dehydration and/or a heart arrhythmia. It can also mean that bone will start to be laid in areas where no bone should be formed, such as inside the blood vessels’ lining, and this could increase the chance of someone suffering from a possibly fatal stroke or heart attack.

It is also important to understand that some people experience side effects from taking vitamin D. This is most common with vitamin D2 supplements, although it can happen with any type of vitamin D exposure, be that through supplementation or through natural sources. Some of the side effects that are common with vitamin D, but that do not (necessarily) mean you have overdosed include:

• Nausea
• Stomach cramps
• General weakness
• Frequent urination

Bear in mind that there have been cases where people have taken massive amounts of vitamin D. In Germany, for instance, parents would give their children six doses of 600,000 IU between the time they were born and the time they were 18 months old. This took place from 1940 to 1960. This means that, in just 18 months, babies would get 3,600,000 IU of vitamin D and still be fine.

Some Examples of Vitamin D Overdose

There have been a few isolated cases of vitamin D overdoses in the world. Most of these were completely accidental. For instance:

• In Massachusetts, 20 people overdosed on vitamin D when their fortified milk was accidentally supplemented with too much vitamin D. It contained around 50,000 IU per cup, instead of the usual 100. Twenty people drank more than average amounts of milk. The mistake was corrected and everyone recovered.

• A young boy of two years was supposed to be given two drops of vitamin D, but received a full ampule instead. This contained 600,000 IU. In total, the boy received 2,4 million IU in the form of four ampules. He developed constipation, colic and sever high calcium. The boy made a full recovery.

• One 60 year old male took a poorly diluted supplement, leading to him taking 1,000,000 IUs per day. He had some elevated calcium levels and experienced mild nausea. Both stopped when he no longer took the supplement. He suffered no long term effects.

• A health guru developed a product known as the ‘Ultimate Power Meal’. When testing it on himself, he suffered constipation and nausea. He found that the meal manufacturer had accidentally fortified the product with 2 million IU. Some of the guru’s clients did suffer kidney damage, although the health guru did not.


Yes, it is possible, if you try very hard, to overdose on vitamin D. However, the risk of having a vitamin D deficiency is far greater and has far more adverse side effects. Yet, for some reason, it seems that doctors are afraid to recommend vitamin D because they worry about toxicity. The phenomenon, while real, is so incredibly rare that you will be hard pushed to find a medical professional who has come across it in their lifetime, even if they have spent many years working in ICU units in large cities.

There are so many drugs that have very significant and dangerous side effects, by contrast. Hundreds of thousands of people are hospitalized every single year. Yet nobody truly worries about these. If you were to take a full bottle of Tylenol or Aspirin, you will most likely die. If you were to take an entire bottle of vitamin D, by contrast, you might actually end up healthier than what you were before!

It is interesting that so many people seem to be so worried about vitamin D overdoses. Yet how often do you hear people talk about other types of vitamin or mineral overdoses? For instance, little to no knowledge exists on selenium, magnesium or iron overdose.

Selenium toxicity is very rare. Iron overdoses kill several children each year. In fact, it is one of the main reasons for accidental child deaths in this country. Yet there does not seem to be any national outcries about this. Selenium overdoses, to make matters worse, can actually occur naturally, which is impossible with vitamin D.

Vitamin D is naturally created in our body after exposure to the sun. There isn’t a single case of vitamin D overdose due to spending time in the sun in the entire medical history of the world. It seems that our body actually has a type of feedback system, which stops the skin from making too much of the vitamin. Yet, spending just 20 minutes in the sun can produce around 20,000 IU. This goes to show just how difficult it would be to overdose.

At the same time, however, we now know that sun exposure can cause cancer and should be avoided as much as possible. This is one of the many reasons why around 60% of people in this country have a vitamin D deficiency. As such, instead of worrying about a vitamin D overdose, you should worry about not having enough and how you will then address that condition.

Resources and References:

Vitamin D Overdose – Information on vitamin D toxicity. (News Medical)
Infant Overdose Risk with Liquid Vitamin D – Risk of vitamin D overdose for infants who are given liquid supplements. (FDA)
Vitamin D Scientists’ Call to Action – Call for higher vitamin D intakes. (Grassroots Health)
The Pharmacology of Vitamin D, Including Fortification Strategies – Recommendations on vitamin D dosage. (Reinhold Vieth, University of Toronto and Mount Sinai Hospital)
Assessment of Dietary Vitamin D Requirements During Pregnancy and Lactation – Vitamin D dosage during pregnancy and lactation. (The American Journal of Clinical Nutrition)