What Are the Symptoms of Too Much Vitamin D?

Taking too much vitamin D can lead to an excess of calcium in the blood, resulting in physical symptoms such as frequent urination, weakness, nausea, and vomiting. Vitamin D toxicity also can lead to kidney or bone problems such as kidney stones.

Vitamin D is a key nutrient that helps your body absorb calcium to help build strong bones. It’s also important for your immune system, nervous system, and muscles. A deficiency in this vitamin has also been linked to mental illnesses such as depression and seasonal affective disorder (SAD).

About 40% of Americans may be deficient in vitamin D, with Black and Hispanic adults facing the highest risk of deficiency. Many people can benefit from increasing their vitamin D intake to sufficient levels through sun exposure, diet changes, or—if needed—supplementation as recommended by a physician.

While a deficiency of this nutrient is a very common problem, it’s also possible—but rare—to have too much vitamin D. Too much vitamin D, also known as vitamin D toxicity or hypervitaminosis D, can pose some serious health risks. This is why discussing any supplementation with your doctor is important to ensure you aren't ingesting a potentially harmful mega dose.

Symptoms of Too Much Vitamin D

What happens if you take too much vitamin D? Some signs that you might be getting an excessive amount of vitamin D include:

• Appetite loss
• Constipation
• Dehydration
• Disorientation
• Dizziness
• Fatigue
• Frequent urination
• High blood pressure
• Irritability
• Muscle weakness
• Nausea
  
• Thirst
• Tinnitus
• Vomiting

If you are experiencing these symptoms, talk to your doctor. Be sure to tell them which supplements, medications, and substances you take, including their dosages. If your doctor suspects that your symptoms might be linked to too much vitamin D, they may administer lab tests to check your blood serum levels. 

Vitamin D toxicity can result in other consequences, including kidney and bone problems. Your doctor may also look for signs of the following problems caused by excess vitamin D.

Hypercalcemia

Taking too much vitamin D can lead to excessive calcium in the blood, which is known as hypercalcemia. Some signs of hypercalcemia include:

• Appetite loss
• Constipation
• Depression
• Headaches
• Memory problems
• Thirst
• Tiredness

Hypercalcemia is defined as having blood serum calcium levels that are two standard deviations above the mean. Normal calcium levels are between 8.5mg/dL and 10.2mg/dL.

Calcium serum levels between 10.5 to 13.9 mg/dL are classified as mild to moderate, but numbers between 14.0 and 16.0 mg/dL are considered a hypercalcemia crisis. 

Kidney Problems

Hypercalcemia caused by excess vitamin D can also lead to kidney problems or even kidney damage. Because having too much vitamin D increases the absorption of calcium, it can result in the formation of kidney stones.

However, evidence also suggests that more serious, long-term kidney damage can also take place. These calcium deposits in the kidneys can lead to a condition known as nephrocalcinosis, which can lead to permanent kidney damage or even kidney failure.

Research has found that when people took more than 3,600,000 international units (IU) of vitamin D3, they were more likely to experience kidney damage. Note that these levels are orders of magnitude beyond what you'd get from a little time in the sun or the average multivitamin.

Bone Problems

While getting enough vitamin D is essential for bone health, too much can actually have a detrimental effect. Some research has found that having too much vitamin D can interfere with the actions of vitamin K2, which is a nutrient that helps keep calcium in the bones.

Research has shown that people who take megadoses of vitamin D are more prone to bone fractures. In another study, participants took either 400 IU, 4,000 IU, or 10,000 IU of vitamin D over a three-year period. Bone density tests showed no improvement over a 400 IU dose and actually showed decreased density in the highest dose group. 

What Causes Vitamin D Toxicity?

Vitamin D toxicity is almost always the result of excess supplementation. Because your body regulates vitamin D production, you are unlikely to develop it as a result of sun exposure (although it has been linked to tanning bed exposure). Foods generally do not contain large amounts of vitamin D, so getting an excessive amount in your diet is unlikely.

People may begin taking vitamin D supplements in order to address a deficiency or to help relieve symptoms of things like seasonal affective disorder or depression. The problem is that they may go overboard or think that taking more will produce more beneficial effects.

Vitamin D Supplement Safety

When exposed to the sun, your body produces vitamin D, but many people may not get enough due to various factors. Because of this, people often turn to vitamin D supplements. Unfortunately, it isn't uncommon for people to overdo it. 

A 2017 study published in the Journal of the American Medical Association (JAMA) found that between 1999 and 2014, the number of American adults taking daily vitamin D supplements of 1,000 IU or more increased. Of these, 18% exceeded 1000 IU each day, and 3% took more than 4,000 IU per day, which may place them at a higher risk of experiencing some adverse effects related to excessive vitamin D.

In most cases, you can get all the vitamin D you need naturally without supplementation through sun exposure and diet. A 15-minute walk outside daily with your extremities exposed can boost vitamin D production. (Remember to wear sunscreen after 15 minutes of exposure, however). 

Eating foods naturally high in vitamin D or fortified with the nutrient can help. Foods you can eat to boost your vitamin D levels include:

• Egg yolks
• Fortified milk, yogurt, or juice
• Cheese
• Fatty fish, such as tuna or salmon
• Cod liver oil

If you take a vitamin D supplement to correct a deficiency or because you cannot get an adequate amount through sunlight and diet, always follow your doctor's guidelines and do not take more than the recommended amount.

Depression and Vitamin D Deficiency

For most people, low vitamin D levels tend to be more of a problem. Deficiency can have a number of health effects, including poor bone health, but it can also impact brain development and functioning. Low levels of vitamin D have been associated with mental health conditions, including seasonal affective disorder, depression, and schizophrenia.

If you are experiencing symptoms of depression, whether or not it's seasonal, talk to your doctor before you try to self-medicate with a supplement like vitamin D. Your doctor can assess your health and determine if vitamin D might help or if some other treatment would be more appropriate.

Final Thoughts

Vitamin D is important for maintaining physical and mental health, is associated with lower rates of certain cancers, and improves mood. However, it is important to use caution if you decide to take a supplement.

There are many supplements on the market, and some promote very high doses of Vitamin D, which can lead to toxic levels. Research suggests that the potential risks of high-dose vitamin D supplementation include an increased risk of kidney stones, muscle pain, mood disorders, digestive issues, and bone fractures.

As is the case with all vitamins, if you are thinking about taking vitamin D supplements, talk to your doctor first about what is right for you.