• Vitamins and Supplements

Too Much of a Good Thing: What is a Vitamin D Overdose?

Medically reviewed and edited by Dina Whiteaker, APRN

Vitamin D has received much attention recently for its powerful health benefits.

Scientists believe this vitamin may be crucial for bone health, immune system support, and preventing cognitive decline.

This vitamin is fat-soluble, meaning it is stored in the body’s fatty tissues, including the liver. It is only released when the body needs it.

Vitamin D can be absorbed into the body through certain substances, such as fortified foods. It is also produced by the body when the skin is exposed to sunlight. Additionally, it can be obtained from a vitamin D supplement.

Although this nutrient is vital for certain functions in the body, high vitamin D levels can have serious health implications.

Learning how much vitamin D is too much – and the symptoms you may experience as a result – can help you regulate your vitamin D levels.

What is Vitamin D Toxicity?

Also known as hypervitaminosis D, vitamin D toxicity occurs when an individual has too much of this nutrient in their body.

Although this is a rare occurrence, it can cause serious health complications. One of the main functions of vitamin D is that it helps the body absorb calcium.

For this reason, the main issue associated with excessive levels of vitamin D is the potential development of hypercalcemia, which occurs when there is too much calcium in the body.

Hypercalcemia is typically what causes the symptoms of vitamin D toxicity.

According to the National Institutes of Health (NIH), there are about 4,500 cases of vitamin D toxicity per year in the U.S., most of which are unintentional or accidental.

What are normal vitamin D levels?

Vitamin D levels are measured through blood tests that measure the concentration of the substance in the body. These levels are measured in nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL).

According to the NIH, vitamin D levels are measured as follows:

What causes too much vitamin D in the body?

Vitamin D toxicity is usually caused by taking supplements that contain this nutrient. People may need to take vitamin D supplements when their levels are too low.

Supplements can be prescribed by a doctor or purchased over-the-counter (OTC).

It is believed that excessive sun exposure will typically not cause vitamin D toxicity.

Since foods usually contain very small amounts of vitamin D, it’s also not likely that people will get too much of this nutrient from what they eat.

One study found that vitamin D toxicity is more common in individuals with the following medical conditions:

• Lymphomas: Cancers of the body’s disease-fighting lymphatic system

• Congenital disorders: Heart defects that often develop before birth

• Granulomatous disorders: Genetic conditions where white blood cells can’t kill bacteria as they should

What are the Symptoms of a Vitamin D Overdose?

Not everyone with vitamin D toxicity will experience symptoms. However, the most common side effects of too much vitamin D are discussed below.

Many of these symptoms can be caused by other health conditions. For this reason, consult with a medical professional if you experience any of these side effects.

Gastrointestinal symptoms

Large amounts of vitamin D in the body can lead to excessive calcium. It is believed that too much vitamin D can cause calcium to leave the bones and enter the bloodstream.

Some of the main symptoms of hypercalcemia are problems within the gastrointestinal system, including:

• Nausea

• Vomiting

• Diarrhea

• Constipation

• Lack of appetite

• Abdominal pain

Kidney stones

High doses of vitamin D may result in the formation of kidney stones in the body. These are calcified masses in the form of crystals that appear in the urinary system.

Kidney stones can vary in size, from small grains to large crystals. When these stones get stuck in the urinary tract, they can cause several symptoms, such as:

• Severe pain in the back or on the side of the body

• Blood in the urine, known as hematuria

• Frequent urination

• An increased urge to urinate

• Pain during urination

• Cloudy or odorous urine

Other kidney problems

Aside from kidney stones, high vitamin D levels in the body can cause other issues with this organ. These can be serious health conditions, including kidney damage and even kidney failure.

This is primarily the result of calcification of the kidneys due to high levels of calcium in the body. It can also result from water loss through frequent urination, which can be caused by too much calcium.

Studies have also found that the hypercalcemia explained above can cause the blood vessels in the kidneys to constrict, leading to reduced kidney function.

Similarly, researchers have discovered that vitamin D toxicity can lead to kidney disease.

Bone health problems

While vitamin D is vital to the health and density of bones in the body, too much of this nutrient can interfere with how calcium is stored in them.

Too much vitamin D can prevent vitamin K2 from keeping calcium in the bones. Additionally, excessive use of vitamin D supplements can result in weakened bones, leading to more fractures

Muscle weakness

As mentioned above, excessive vitamin D can disrupt the calcium balance in the body, which can interfere with normal muscle functioning. This may cause muscle fatigue and weakness.

Mental health symptoms

Some research indicates that high levels of vitamin D in the body can lead to altered mental states, including confusion, depression, and even psychosis.

Severe hypercalcemia

Hypercalcemia can be a life-threatening condition and requires immediate medical attention. Besides gastrointestinal problems, hypercalcemia can also cause:

• Fatigue

• Hallucinations and confusion

• Dizziness

• Excessive urination

• High blood pressure

• Dehydration

• Muscle weakness

How is a Vitamin D Overdose Treated?

Your doctor will diagnose vitamin D toxicity by running blood tests. These tests will determine the vitamin D and calcium levels in your body.

They may also run a kidney function test to identify if this organ is being affected by vitamin D intoxication.

Treatment for vitamin D toxicity will typically involve stopping all intake of this nutrient. It may also include restricting dietary calcium intake.

Your healthcare provider may also prescribe intravenous (IV) fluids and medications like corticosteroids — which are anti-inflammatory drugs.

Additionally, you may need to take bisphosphonates which is a medication typically used to prevent the loss of bone density.

According to the NIH, treatment may include avoiding bed rest, as immobility can lead to hypercalcemia.

How to Prevent Vitamin D Toxicity

If you are considering taking vitamin D supplements, it’s important that you consult a healthcare provider first.

Should a healthcare professional prescribe a vitamin D supplement for you to take, ensure you follow their recommendations closely.

When taking high-dose vitamin D, it’s vital that you have regular blood tests carried out to ensure your levels aren’t too high.

In most cases of vitamin D toxicity, people can make a full recovery without serious complications.

How Much Vitamin D Do I Need?

To avoid vitamin D toxicity, knowing how much of this nutrient you should get each day is important.

Remember, vitamin D comes from food, sun exposure, and nutritional supplements.

The NIH recommends the following daily amounts of vitamin D, measured either in micrograms or International units — a metric used to measure substances like vitamins and minerals.

When to Seek Medical Assistance for Vitamin D Toxicity

If you have been taking vitamin D or calcium supplements and you’re experiencing the symptoms outlined above, seek immediate medical attention. Vitamin D toxicity can lead to life-threatening conditions.

Where Can I Learn More About Vitamin D Toxicity?

With LifeMD, you have online access to board-certified physicians and nurse practitioners.

Schedule a telehealth appointment with a licensed medical professional to learn about healthy vitamin D intake and whether you should take dietary supplements.

Dina Whiteaker, APRN

Dina earned her MSN from the University of Nebraska Medical Center before becoming a Family Nurse Practitioner. She has 10ᐩ years of telemedicine experience. Dina is board certified and is a member of the American Academy of Nurse Practitioners.

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