Could You Have Too Much Vitamin D?
Medically reviewed by Jamie Johnson, RDN
Vitamin D plays an important role in maintaining health. However, too much can be harmful and cause symptoms like stomach discomfort, unusual mental symptoms, or kidney problems. It is a fat-soluble vitamin that can build up in your tissues if you take too many vitamin D supplements.
A blood test can help determine if you have too much vitamin D, known as vitamin D toxicity. This article covers the signs and symptoms of too much vitamin D, the side effects of taking vitamin D supplements, and more.
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Signs and Symptoms of Taking Too Much Vitamin D
Vitamin D is required to maintain health. It also acts as a hormone, contributing to many processes in the body. Because it is fat-soluble, vitamin D is stored in the body’s fatty tissue and the liver.
While getting enough vitamin D to support your health is important, too much can be a problem. Below are the signs and symptoms of taking too much vitamin D, also known as hypervitaminosis D.
Elevated Vitamin D Blood Levels
A healthcare provider can order a blood test to check your vitamin D level. High serum (blood) levels of vitamin D are defined as greater than 100 nanograms per milliliter (ng/mL), with adverse effects seen particularly at greater than 150 ng/mL.
Optimal blood vitamin D levels are generally between 30 ng/mL and 60 ng/mL. Experts do not believe that excessive sun exposure results in vitamin D toxicity due to how sunlight activates different forms of vitamin D in the skin.
Vitamin D toxicity is rare, and most cases of vitamin D toxicity are caused by inappropriate supplement dosing and prescription errors.
For example, a review of case reports of vitamin D toxicity found that many resulted in the overcorrection of vitamin D deficiency. In these cases, people presented with vitamin D levels well above optimal, ranging between 150 to 1,220 ng/mL.
It’s important to note that people with low vitamin D blood levels may need higher supplemental doses to meet and maintain an optimal vitamin D status. However, a healthcare provider should monitor this higher intake closely, checking blood vitamin D levels regularly to ensure they do not rise to toxic levels.
Consult a healthcare provider before taking vitamin D supplements. They can help guide you on the appropriate dosage you should take.
Elevated Calcium Levels
One of the main roles of vitamin D is to increase calcium absorption in the gastrointestinal (GI) tract. Because of this, vitamin D toxicity also results in hypercalcemia (blood calcium levels above normal) and hypercalciuria (excess calcium in the urine).
If you have too much vitamin D in your blood, your blood calcium levels should also be assessed. Normal blood calcium levels are 8.4 to 10.2 milligrams per deciliter (mg/dL). Hypercalcemia is defined as blood calcium levels greater than 10.5 mg/dL.
Most of the symptoms seen with vitamin D toxicity are related to the associated hypercalcemia, which can be life-threatening.
These symptoms include:
Vomiting
Neuropsychiatric disturbances
Pain
In general, research shows that vitamin D-associated hypercalcemia only happens when extremely large doses of vitamin D, such as over 10,000 International Units (IU) per day, are taken over time.
Seek medical attention if you are experiencing symptoms related to vitamin D toxicity or hypercalcemia.
Gastrointestinal Symptoms
The most common side effects of too much vitamin D are related to hypercalcemia. This leads to GI-related symptoms, such as:
Nausea
Vomiting
Loss of appetite
Altered Mental Health
Aside from the physical symptoms associated with too much vitamin D and related hypercalcemia, there may also be symptoms related to mental health. These include:
Confusion
Apathy (lack of interest, enthusiasm, or concern)
Irritability
Stupor (in extreme cases)
Coma (in extreme cases)
For example, one case study reported hypercalcemia in a 64-year-old person due to excess vitamin D supplementation of 200,000 IU daily. This resulted in altered mental status, along with other physical symptoms related to hypercalcemia.
The person was hospitalized and continued to be agitated and confused for 10 days, with blood calcium levels returning to normal after 18 days.
Kidney Complications
Too much vitamin D and the related hypercalcemia can lead to kidney complications, such as decreased kidney function, kidney injury, renal failure, and kidney stones. People with kidney disease also need to prevent taking too much vitamin D, as it can lead to serious kidney complications.
Numerous case studies have reported kidney complications related to excess vitamin D intake.
For example, a 65-year-old male took injections of 50,000 IU of vitamin D per week for one year. Upon admission to the hospital, he had acute (short-term) kidney injury, among other symptoms. Prompt treatment improved symptoms and avoided further damage to his kidneys.
Another case study involved a 54-year-old male who presented with a suspected kidney injury. Upon investigation, it was found that he was taking 8,000–12,000 IU of vitamin D drops daily for roughly 2.5 years.
Both his blood vitamin D and calcium levels were very high. After undergoing treatment for nearly one year, his calcium and vitamin D levels returned to normal. However, he was left with stage 3B chronic kidney disease.
How Much Vitamin D to Take Per Day
The recommended dietary allowance (RDA) for vitamin D for healthy people ages 1 to 70 years is 600 IU, or 15 micrograms (mcg), per day. It’s recommended for people over age 70 to get 800 IU, or 20 mcg daily.
This amount includes vitamin D you get from food, as well as dietary supplements.
Vitamin D is found naturally in a few foods, such as fatty fish (salmon, tuna trout), beef liver, egg yolks, and mushrooms treated with ultraviolet (UV) light. Vitamin D is added, or fortified, to some foods to increase intake in American diets. Commonly fortified foods include milk and breakfast cereals.
If your vitamin D levels are low, talk with a healthcare provider to determine how much vitamin D you should take to help bring it to optimal status.
Signs of a Vitamin D Deficiency
Most people in the United States do not consume the recommended amount of vitamin D.
People can develop a vitamin D deficiency for various reasons, such as when their intake is below the recommended amount, they do not have adequate sun exposure, their body cannot convert vitamin D to its active form, or they have trouble absorbing it from the GI tract.
In children, severe vitamin D deficiency leads to rickets, a disease characterized by bowed legs due to softening of the bones. In the United States, rickets is most common among breastfed Black infants and children.
Other populations at risk of developing vitamin D deficiency are older adults, people with limited sun exposure, people with dark skin, people with conditions that limit fat absorption, and people with obesity or who have undergone gastric bypass surgery.
Other signs of severe vitamin D deficiency in children include failure to thrive, developmental delay, and dental abnormalities. Also, vitamin D deficiency can result in hypocalcemia (low blood calcium levels), leading to cardiomyopathy (a disorder affecting the heart muscle), hypocalcemic seizures, and tetanic (muscle) spasms.
In adults, vitamin D deficiency can lead to osteomalacia (loss of bone minerals) and osteoporosis (porous, thinning bones). Symptoms include:
Weak bones
Bone pain
Muscle weakness
Bone deformities
Dental abnormalities
Testing Vitamin D Levels
Vitamin D status is tested by drawing blood to measure 25 hydroxyvitamin D, or 25(OH)D, in your blood. A healthcare technician or nurse will collect a small amount of blood from your arm into a test tube or vial using a small needle. The process usually takes less than five minutes.
The 25(OH)D level is the most accurate way to measure how much vitamin D is in the blood. It reflects vitamin D produced endogenously (inside the body) and obtained from diet and supplements.
Possible Vitamin D Side Effects
Generally, eating foods with vitamin D in them is well tolerated, and there are no known side effects from vitamin D produced as a result of sunlight exposure.
Supplemental vitamin D3 may cause some side effects, such as:
Loss of appetite
Weight loss
Nausea
Vomiting
Constipation
Contact a healthcare provider if you experience these or any unusual symptoms while taking vitamin D supplements.
Summary
Vitamin D is a fat-soluble vitamin and hormone that is involved in many processes in the body to support and maintain good health. One of the main roles of vitamin D is to promote calcium absorption in the gut to help maintain normal blood calcium levels.
You cannot get too much vitamin D from diet or sunlight exposure, but you can get too much from supplements. Too much vitamin D can cause health problems, including high blood calcium levels, kidney problems, and gastrointestinal problems such as nausea, vomiting, loss of appetite, and constipation.
Too much vitamin D can also lead to altered mental health, such as confusion, apathy, depression, irritability, hallucinations, and psychosis. Vitamin D status is measured using a blood test.
Most people in the United States do not consume the recommended amount of vitamin D. Signs of vitamin D deficiency include weak bones, bone pain, muscle weakness, bone deformities, and dental abnormalities.
Possible side effects of supplemental vitamin D3 include loss of appetite, weight loss, nausea, vomiting, and constipation.
Read the original article on Verywell Health.
