Side Effects of Taking Too Much Vitamin D

Recent research suggests that ~ 40% of Europeans are deficient in vitamin D, and 13% are severely inadequate. In some countries like India, the figure reaches around 490 million people. (1)

Vitamin D is essential for good health. It performs various functions in our body and serves to keep cells working as they should.

Aside from fatty fish, there are few foods rich in vitamin D. Also, most people don’t get enough sun exposure to make adequate vitamin D. For these reasons; supplements are increasingly common.

However, it is also possible for this vitamin to accumulate and reach toxic levels in your body. This article looks at what vitamin D supplements are for and the possible side effects of consuming excessive amounts of this vital vitamin.

What is vitamin D, and what is it for?

Vitamin D (also known as “calciferol”) is a fat-soluble vitamin that occurs naturally in some foods and is available as a dietary supplement. It is also produced endogenously when sunlight’s ultraviolet (UV) rays hit the skin.

Vitamin D promotes calcium absorption in the intestine and maintains adequate calcium and phosphate concentrations in the blood. This serves to allow normal mineralization of the bones and prevent cramps.

Bones can become thin, brittle, or misshapen without enough vitamin D. Along with calcium, vitamin D also helps protect older adults from osteoporosis.

Vitamin D has other functions in the body, including reducing inflammation and modulating processes such as cell growth, immune, neuromuscular function, and glucose metabolism. (3)

Vitamin D toxicity

Vitamin D poisoning occurs when blood levels exceed 150 ng/ml. Because the vitamin is stored in body fat and slowly released into the bloodstream, the effects of toxicity can last for even several months after you stop taking supplements.

Importantly, toxicity is uncommon and occurs almost exclusively in people who take long-term, high-dose supplements without controlling their blood levels. On the contrary, poisoning cannot be achieved solely through diet and exposure to the sun.

Several studies have questioned the relevance of this general recommendation to take vitamin D and the need to supplement with supplements when not necessary. (1)

“Vitamin D is not a panacea, and it is most likely only effective in cases of deficiency. But given its rare side effects and relatively wide safety margin, it could be an important, inexpensive, and safe therapy for many diseases. ” – Writes Karin Amrein European Journal of Clinical Nutrition.

Karin insists that the use of vitamin D supplements on a large scale is still up for debate. And according to their review, no clinical benefits have been found in individuals getting enough of it. So it suggests that large and well-designed future studies should further evaluate this.

Five side effects of taking too much vitamin D

Here are the top 5 side effects of taking more vitamin D than you need:

  1. Elevated levels of calcium in the blood

Vitamin D helps your body absorb calcium from the food you eat. This is one of your most important roles.

However, if the intake of vitamin D is too much, the calcium in the blood can reach levels that can cause unpleasant symptoms, potentially dangerous.

Symptoms of hypercalcemia or high levels of calcium in the blood include:

  • digestive upset, such as vomiting, nausea, and
  • stomach ache
  • fatigue, dizziness, and confusion
  • but excessive
  • frequent urination
  1. Nausea, vomiting, and poor appetite

Many side effects of too much vitamin D are related to too much calcium in the blood. These include nausea, vomiting, and poor appetite.

One study followed 10 people who had developed calcium levels after taking high doses of vitamin D to correct an excessive deficiency. Four of them experienced nausea and vomiting, and three lost their appetite. (4)

Similar responses to megadose doses of vitamin D have been reported in other studies. One woman experienced nausea, weight loss, confusion, and listlessness after taking a supplement that contained 78 times more vitamin D than is indicated on the label. (8)

Notably, these symptoms responded to extremely high doses of vitamin D3, which led to calcium levels above 12 mg/dl.

  1. Stomach pain, constipation, or diarrhea

Stomach pain, constipation, and diarrhea are common digestive complaints related to food intolerances or irritable bowel syndrome.

However, they can also signify elevated calcium levels caused by vitamin D poisoning.

These symptoms can occur in those who receive high doses of vitamin D to correct the deficiency. As with other symptoms, the answer appears to occur even when blood levels of vitamin D are high.

  1. Kidney failure

The kidneys play an essential role in making vitamin valuable d to the body. The kidneys convert vitamin D from supplements or the sun into its active form.

However, excessive intake of vitamin D often results in kidney damage. Most studies have reported moderate to severe kidney injury in people who develop vitamin D toxicity. (6)

In a study of 62 people who received excessively high doses of vitamin D injections, all people experienced kidney failure, whether they had healthy kidneys or existing kidney disease. (5)

This is because excess vitamin D in the form of supplements can modify the activity of one type of immune cell: infiltrating macrophages of the kidney. (7)

  1. Bone loss

Because vitamin D plays a vital role in calcium absorption and bone metabolism, getting enough is crucial to maintaining strong bones.

Instead, too much vitamin D can be detrimental to bone health. Although many symptoms of excess vitamin D are attributed to high calcium levels in the blood, some researchers suggest that megadoses can cause low levels of vitamin K2 in the blood.

One of the most important functions of vitamin K2 is to keep calcium in the bones and out of the blood. Very high levels of vitamin D are believed to reduce the activity of vitamin K2.

To protect against bone loss, avoid taking excess vitamin D supplements. You can also eat foods rich in vitamin K2, such as grass-fed dairy and meat.


Ensuring your body enough vitamin D is essential to staying healthy. The recommended amount per day is ten micrograms (400 IU) of vitamin D per day for most people.

However, it is essential to understand excess vitamin D can be toxic. So you should also make sure to avoid extreme dosages. Up to 400 ug – 4,000 IU per day is considered the safe maximum, as long as your blood values ​​are monitored.

Even if you eat a healthy diet, you may need supplements to achieve optimal blood levels. However, you need to understand that too much vitamin D can be toxic.

Also, buy supplements from quality manufacturers to reduce the risk of accidental overdose due to improper labeling.

If you have been taking vitamin D supplements and are experiencing any of the symptoms listed in this article, see a healthcare professional as soon as possible.

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