Vitamin D: Benefits, Deficiency, Sources And Risks

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Medical News TodaySubscribeCan too much vitamin D hurt you?

Medically reviewed by Alexandra Perez, PharmD, MBA, BCGP — Written by Jennifer Huizen — Updated on February 9, 2023

Overview
Hypercalcemia
Kidney damage
Cardiac conditions
Brittle bones
Dehydration
Pancreatitis
Side effect frequency
Who should avoid it?
Too much vitamin D
Summary

Long-term use of high dose vitamin D supplements may cause adverse side effects, such as dehydration, nausea, vomiting, cardiovascular problems, and confusion.

The Office of Dietary Supplements notes that toxicity is unlikely on a daily dose of 250 microgram (mcg) or less. However, they point out that even these levels or lower may have adverse effects in the long term.

This article details the role of vitamin D in the body and the potential side effects of overexposure.

What is vitamin D?

Several gold pill capsules against a dark background. — Raymond Forbes LLC/Getty Images

Vitamin D is a fundamental nutrient that supports several bodily processes, including:

the absorption and regulation of calcium, magnesium, and phosphate
the hardening, growth, and remodeling of bones
immune function
nerve and muscle function

Many people get enough vitamin D from sun exposure and their diet. Some choose to take supplements.

How much vitamin D should a person take?

A person’s daily vitamin D requirement depends on several individual factors, such as age, sex, and health status.

Doctors consider vitamin D levels adequate if a person has at least 20 nanograms (ng) of the vitamin per milliliter (mL) of blood. If levels rise above 50 ng/mL, a person may experience adverse side effects.

Below are some of the most serious side effects of over-supplementing vitamin D.

Hypercalcemia

Many of the significant side effects of vitamin D toxicity are related to hypercalcemia. Hypercalcemia refers to having excess calcium in the blood.

Researchers often cite this threshold as 10.4 mg of calcium per deciliter (dL) of blood, or as 0.104 mg/mL.

Hypercalcemia has three stages:

Hypercalcemia stage	Calcium levels
Mild hypercalcemia	10.5–11.9 mg/dL
Moderate hypercalcemia	12.0–13.9 mg/dL
Hypercalecemic crisis	14.0–16.0 mg/dL

There is a strong relationship between vitamin D and calcium. Vitamin D increases calcium absorption in the gastrointestinal tract. Having too much calcium can lead to a wide range of complications and symptoms.

Some of the most serious include:

a loss of appetite and increased thirst
diarrhea or constipation
nausea
confusion, disorientation, or trouble thinking
joint and muscle pain or weakness
continuous headache
high blood pressure

Kidney damage

Excess calcium in the body due to vitamin D toxicity may promote the development of kidney stones in people who are predisposed to the condition.

Excess calcium in the bloodstream binds with phosphate, forming crystals that deposit in soft body tissues. These crystals can cause tissue damage and eventually organ damage, depending on their location, number, and size.

When the crystals get stuck in kidney tissues, nephrocalcinosis (kidney stones) can occur. If this condition is severe, it can cause permanent kidney damage and kidney failure.

Symptoms of nephrocalcinosis include:

blood in urine
nausea and vomiting
fever and chills
severe pain in the stomach, the sides of the back, or the groin area

Irregular heartbeat and heart attack

Vitamin D levels have links to heart disease and a person’s risk of cardiovascular disease.

Extreme hypercalcemia can reduce the functionality of cells in the heart. People with severe hypercalcemia may also experience irregularities in their heartbeat.

A person with severely high levels of calcium or phosphate in the blood may also develop calcium deposits, or plaques, in the arteries or valves of the heart.

Some signs of heart complications associated with vitamin D toxicity include:

an irregular heartbeat, which may be temporary or continual
drowsiness
high blood pressure

Brittle bones and bone pain

Vitamin D toxicity can cause hypercalcemia and subsequent problems with the bones, including a loss of bone density.

Some symptoms include:

aching or painful bones
bones that are prone to fractures or breaks
bone cysts
gait abnormalities

Dehydration

Elevated calcium levels in the blood can harm the kidneys’ ability to concentrate urine. This may result in a person producing and passing unusually large quantities of urine, known as polyuria.

When a person passes diluted urine, they lose large quantities of water and electrolytes. For this reason, a person with vitamin D toxicity may be prone to dehydration.

Symptoms of moderate dehydration include:

a dry mouth and tongue
increased thirst
dark-colored urine
headache
feeling tired

Severe dehydration can result in life threatening conditions. Other signs and symptoms of this condition include:

rapid heartbeat and breathing
confusion
fainting
lack of urination
low blood pressure
unexplained exhaustion

Pancreatitis

Hypercalcemia can cause acute pancreatitis, which is the term for inflammation of the pancreas.

A 2017 review found that 2 of 19 people with vitamin D toxicity experienced acute pancreatitis as a complication. Each had taken an average of 6,000,000 international units (IU) of the vitamin over 1–3 months.

Signs of pancreatitis include:

upper stomach pain that extends to the back
nausea and vomiting
a rapid pulse
swollen or tender abdomen
fever

How common are side effects?

A 2018 study found there has been an increase in the incidence of vitamin D toxicity due to more people supplementing vitamin D without a doctor’s supervision. However, symptomatic vitamin D toxicity remains rare.

High vitamin D levels typically result from consuming excessive amounts of high dose dietary supplements. A person cannot get too much vitamin D from the sun.

The 2018 study also found that certain high dose vitamin D formulations (50,000 IU doses) were common in people with elevated vitamin D levels.

The body stores vitamin D in fat tissues, and it can take weeks or months for the effects of vitamin D toxicity to fully wear off.

Who should avoid vitamin D?

Dietary vitamin D supplements are useful when it is not possible to otherwise meet the recommended vitamin D requirements. However, vitamin D supplements are not suitable for everyone.

People with the following conditions are at a higher risk of vitamin D toxicity and should consult a healthcare professional before taking any supplements:

granulomatous disorders, such as sarcoidosis or tuberculosis
some lymphomas
idiopathic infantile hypercalcemia
Crohn’s disease

Vitamin D drug interactions

Vitamin D supplements can interact with some medications.

For example, high dose vitamin D supplements can reduce the efficacy of cholesterol-lowering statins such as atorvastatin. A doctor will assess a person’s health status before prescribing statins. It is essential to follow medical guidance when taking any medications.

Other medications can affect a person’s vitamin D levels.

Steroids: Steroids such as prednisone can lower vitamin D levels.
Orlistat: This weight loss medication can decrease vitamin D absorption rates.
Thiazide diuretics: These medications can raise a person’s blood calcium levels if they take them alongside vitamin D supplements.

While these outcomes are not the direct result of drug interactions, it is important to be aware of them. A person should always consult with a healthcare professional before taking supplements.

Signs of too much vitamin D

Symptoms of vitamin D toxicity include:

unexplained exhaustion
dry mouth
increased thirst and frequency of urination
nausea and vomiting
confusion, disorientation, or trouble thinking
irregular heartbeat

Health risks of too much vitamin D

People with severe or chronic vitamin D toxicity may develop life threatening symptoms, including:

extreme dehydration
high blood pressure
slowed growth
trouble breathing
temporary losses of consciousness
heart failure or heart attack
kidney stones or kidney failure
hearing loss
tinnitus (ringing in the ears)
pancreatitis (inflammation of the pancreas)
gastric ulcers
coma

Summary

Vitamin D toxicity can cause a wide range of symptoms, and each individual may respond differently.

A person may have a higher risk of experiencing toxicity if they take high dose supplements over an extended period. Doing this can cause vitamin D to build up in the blood.

The risk of experiencing adverse side effects from vitamin D in the diet or through exposure to the sun is very low.

Dermatology
Nutrition / Diet
Complementary Medicine / Alternative Medicine

How we reviewed this article:

SourcesMedical News Today has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

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Dehydration. (2019)https://medlineplus.gov/dehydration.html
Hyperparathyroidism. (2021).https://www.nhs.uk/conditions/hyperparathyroidism/
Knoll, K., et al. (2018). Management of hypercalcemia-induced heart failure using mechanical circulatory support.https://academic.oup.com/ejcts/article/54/4/784/4956920
Lee, J. P., et al. (2018). Vitamin d toxicity: A 16-year retrospective study at an academic medical center.https://academic.oup.com/labmed/article/49/2/123/4807321?login=true
Letavernier, E., et al. (2018). Vitamin D, hypercalciuria, and kidney stones.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5872784/
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Marcinowska-Suchowierska, E., et al. (2018). Vitamin D toxicity–A clinical perspective.https://www.frontiersin.org/articles/10.3389/fendo.2018.00550/full
Mulay, S. R., et al. (2019). A guide to crystal-related and nano- or microparticle-related tissue responses.https://febs.onlinelibrary.wiley.com/doi/full/10.1111/febs.15174
Nephrocalcinosis. (2021).https://rarediseases.info.nih.gov/diseases/7177/nephrocalcinosis
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Sadiq, N. M., et al. (2021). Hypercalcemia.https://www.ncbi.nlm.nih.gov/books/NBK430714/
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Medically reviewed by Alexandra Perez, PharmD, MBA, BCGP — Written by Jennifer Huizen — Updated on February 9, 2023

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