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Oct 31, 2024

Vitamin D Overdose Symptoms You Shouldn't Ignore

fotostorm / Getty Images Taking too much vitamin D in supplement form can lead to vitamin D toxicity, a rare but potentially dangerous condition. This vitamin D overdose shows up as higher calcium

fotostorm / Getty Images

Taking too much vitamin D in supplement form can lead to vitamin D toxicity, a rare but potentially dangerous condition. This vitamin D overdose shows up as higher calcium levels in the blood or hypercalcemia. Symptoms may include digestion problems, increased urination, fatigue, confusion, bone pain, and high blood pressure.

Vitamin D toxicity is more common in people with certain medical conditions, such as granulomatous disorders, spina bifida, lymphomas, and dysregulated vitamin D metabolism.

In the United States, the Food and Drug Administration (FDA) does not regulate supplements the way it regulates prescription drugs. That means some supplement products may not contain what the label says. When choosing a supplement, look for third-party tested products and consult a healthcare provider, registered dietitian nutritionist (RD or RDN), or pharmacist.

Excessive effects of vitamin D can lead to higher calcium levels in the blood—a condition called hypercalcemia. It is often diagnosed at an early stage during routine blood work.

Most people with hypercalcemia will not have symptoms. However, symptoms can occur in people who have taken high doses of vitamin D for a long time or in someone who has taken an extremely high dose over a short time.

Symptoms caused by high calcium levels can vary, depending on the cause and how long levels have been elevated. Symptoms may include:

Higher doses may cause more severe side effects, mainly a weekly 20,000 to 50,000 international unit (IU) dosing, the highest prescribed dose. However, long-term supplementation of vitamin D3 in doses ranging from 5,000 to 50,000 IU appears safe when taken correctly.

Higher doses are typically prescribed to people whose bodies do not adequately process vitamin D due to some health conditions. Such conditions include asthma, psoriasis, rheumatoid arthritis, rickets, and tuberculosis. The higher dose is often prescribed to correct or prevent deficiency.

Many people do not have side effects from the 50,000 IU dose, but this high dose should only be taken under a healthcare provider's supervision. Never take high doses of vitamins or supplements without a healthcare provider's approval.

The daily recommended dose for children ages 1 to 18 and adults is 600 IU. The numbers are less for babies and higher for adults over age 70. Healthcare providers might prescribe higher or lower doses based on specific health concerns.

Supplementing with vitamin D can lead to side effects. It can also lead to longer-term but rare problems. Such rare effects include:

If you take high doses of vitamin D and experience symptoms of hypercalcemia, let your healthcare provider know. They can request blood work to check your vitamin D, calcium, and phosphorus levels. A phosphorus test helps determine if you have kidney damage.

Healthcare providers consider vitamin D levels low if a person has 20 nanograms (ng) of vitamin D per milliliter (mL) of blood or lower. If levels rise above 50 ng/mL, you might experience adverse effects.

Some people are at a higher risk for vitamin D deficiency (insufficient vitamin D). They include:

Researchers suspect people with dark skin tones get less vitamin D because the higher level of melanin in darker skin limits the rate of skin synthesis. This is when the top layer of your skin (epidermis) activates (synthesizes) vitamin D when exposed to the sun's ultraviolet (UV) radiation.

People in the above-listed groups can benefit from vitamin D supplementation throughout the year and not just in the winter months, when there is less sun exposure.

Vitamin D toxicity is rare, even in people who take supplements. For symptoms of toxicity to present, you would need to take significant doses over a long period. Even so, research suggests that with the increasing use of vitamin D treatments, incidents of toxicity have become more frequent.

Many of the causes of vitamin D toxicity are inappropriate prescribing, not taking vitamin D as prescribed, and the use of high-dose and unlicensed preparations. Many cases are preventable with appropriate use, proper formulation, and avoidance of unlicensed products.

Vitamin D toxicity is more common in people who have certain medical conditions. This includes people with:

In people with dysregulated vitamin D metabolism, vitamin D intake raises the concentration of vitamin D in the body, leading to toxicity.

Hypercalcemia related to vitamin D toxicity might alter a person's mental state. Symptoms of an induced mental state related to vitamin D-induced hypercalcemia include confusion, depression, and psychosis. In rare cases, a coma might occur.

One study examined the case of a 64-year-old man who accidentally took 200,000 IU of vitamin D because he did not understand the medication instructions. He showed an altered mental state and other severe hypercalcemia symptoms.

The man was agitated and confused for the first 10 days of his hospital stay, but symptoms started to improve as his calcium levels dropped. It took 18 days for his calcium levels to get back to normal.

Vitamin D toxicity can lead to a kidney injury or kidney failure. Too much vitamin D causes high calcium levels, leading to water loss from too much urination and kidney calcification.

Hypercalcemia can also lead to blood vessel constriction and decreased kidney function. It might cause severe complications in people who have existing kidney disease, such as anemia (reduced blood cells), bone weakness, and severe swelling from fluid retention.

The term "vitamin D flush" refers to removing excess vitamin D from the body. While there is no quick way to do this, the first step is to stop taking vitamin D and calcium supplements.

The management of vitamin D toxicity has three stages. The first of these is stabilization and supportive therapies, which might include intubation, intravenous fluids, and intensive care for people with extremely high vitamin D and calcium levels.

Additional measures include correcting hypercalcemia using loop diuretics, bisphosphonates, glucocorticoids, or calcitonin (bone hormone drug), and renal replacement therapies if the kidneys have been affected.

If you are taking vitamin D supplements or a prescribed higher dose and start to experience signs of hypercalcemia, let your healthcare provider know. They will request blood work to check vitamin D and calcium levels. Depending on those results, they may reduce your vitamin D dosing or have you stop taking supplements altogether.

Taking vitamin D in high-dose supplements is never a good idea without checking with a healthcare provider. Discuss supplementation with a healthcare provider to ensure you are taking appropriate doses.

While it is rare, vitamin D toxicity can occur, manifesting as hypercalcemia. Common signs of hypercalcemia include digestive problems, fatigue, appetite loss, frequent urination, high blood pressure, and heart abnormalities. Complications of hypercalcemia include an altered mental state and kidney problems.

Vitamin D toxicity is more common in people who have medical conditions where it is necessary to prescribe higher supplement doses. To reduce your risk, avoid high doses and do not start taking supplements without approval from a healthcare provider.

If you are on a higher dose prescribed by a healthcare provider, you should report side effects and get your blood work tested regularly.

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By Lana BarhumBarhum is a freelance medical writer with 15 years of experience with a focus on living and coping with chronic diseases.