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Signs of Vitamin D Overdose: What to Look Out For

Updated on August 4, 2021
Written by
Joel
6 sources cited
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Vitamin D is a fat-soluble molecule that belongs to the same family as vitamins A, E, and K. It has several critical functions in the human body. As we shall learn in this article, having too much (or too little) can have adverse effects.

Importance of Vitamin D

Vitamin D has several critical functions. It regulates the absorption of phosphorous and calcium and facilitates optimal immune response. Optimal amounts of vitamin D will also promote normal growth and development of the bones and teeth.

Sources of Vitamin D

There are two natural ways to get vitamin D. First is from sun exposure, and the next is from food

Examples of Vitamin D-rich foods include:

  • Beef liver
  • Egg yolks
  • Cheese
  • Fatty fish like mackerel, tuna, and salmon
  • Vitamin D fortified foods like orange juice, dairy, cereals, and soy milk

A dietary tip for you:

  • Salmon is one of the richest food sources of vitamin D. Three ounces of cooked salmon contain as much as 570 international units.
  • You may also get vitamin D from dietary supplements. However, it is advised that you consult your doctor on the appropriate dosage before you do.

How Much Vitamin D is Too Much?

It depends on your age. The recommended daily intake, or the recommended dietary allowance, varies by age group, as shown below. In a few circumstances, your healthcare provider may recommend lower or higher doses than your recommended intake.

  • Babies (0-6 months): 400 IU per day
  • Babies (6-12 months): 400 IU per day
  • Children (1-3 years) years: 600 IU per day
  • Children (4-8): 600 IU per day
  • Children, adolescents, and adults (9-70): 600 IU per day
  • Pregnant women or lactating mothers between 14-50 years old: 600 IU

Note: The recommended amounts are expressed in International Units (IU). The International unit (IU) is the quantity of a substance, like a hormone, vitamin, or toxin, that produces a specific effect when evaluated according to internationally recognized biological procedures.

If you're taking a vitamin D supplement, the label will list the amounts each pill contains, either in micrograms or International units. Sometimes, the amounts won't be listed directly, but they will still provide a daily percentage value. It will show the amount of vitamin D within each serving as a percentage of 800 UI. You may also obtain estimates of the Vitamin D levels in various foods by consulting the National Institute of Health.

Causes of Vitamin D Overdose

The most common cause of Vitamin D overdose, or hypervitaminosis D, is excessive supplementation. It is highly unlikely that overdosage will happen because of sun exposure. This is because The body regulates vitamin D production. Tanning bed exposure, however, is another story.

A person is also highly unlikely to get excessive Vitamin D from their diet because generally, foods do not contain large amounts of Vitamin D.

People usually take Vitamin D supplements to address a deficiency. Supplements are also given to people with depression or seasonal affective disorder. The problem lies when people go overboard with supplementation because they think that taking more will have more beneficial effects. 

Taking a high-dose vitamin D supplement without your doctor’s advice is never a good idea as it carries health risks for you. While Vitamin D supplementation is good, it is best discussed with your doctor.

Signs of Vitamin D Overdose

Having too much Vitamin D in the body can cause health problems if left untreated. However, before it causes severe health conditions, vitamin D toxicity will almost always show initial signs and symptoms indicating overdosage. These include:

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

If you take Vitamin D supplements and start seeing the signs and experiencing the symptoms listed above, talk to a health professional about it. 

Health Effects of Too Much Vitamin D

Vitamin D is very important to the human body. It helps promote good health by making sure that the body’s cells are functioning properly. However, very high levels of Vitamin D can be toxic and can impact the body negatively. Here are some health effects of too much Vitamin D:

Hypercalcemia

High doses of vitamin D can cause dangerous amounts of calcium to build up in your circulatory system, a condition known as hypercalcemia. It occurs when your blood serum calcium levels are two standard deviations above average. 

Normal calcium levels lie between 8.8 and 10.8mg/dl. Hypercalcemia patients typically present with blood calcium levels between 14.0 and 16.0 mg/dl. Some signs of this may include constipation, reduced appetite, headaches, memory problems, tiredness, and thirst.

Additionally, having excessive calcium levels in the blood can cause abnormal heart rhythms. 

Frequent urination

If you take too much vitamin D, it will increase the calcium levels in your blood. This may manifest as frequent urination accompanied by other signs like nausea, vomiting, and others.

Kidney Problems

Left untreated, hyperkalemia resulting from vitamin D toxicity may cause kidney problems and kidney damage. Too much vitamin D increases calcium absorption, which often leads to the formation of kidney stones.

Unfortunately, the condition can get worse. Studies suggest that vitamin D toxicity may lead to severe long-term kidney damage. Calcium deposits in the kidneys may cause nephrocalcinosis, which can lead to permanent kidney failure.

The toxicity levels that would cause this condition are far above what you'd get from basking in the sun or consuming vitamin D-rich foods, so there is not much cause for concern if your health routine includes any of those activities. However, you are at significant risk if you frequently have large doses of vitamin D supplements.

Bone problems

Modest amounts of Vitamin D are good for bone health. But, too much will have the opposite effect, especially if it's against medical advice. Studies suggest that excessive vitamin D levels will interfere with the action of Vitamin K2, which facilitates the absorption of calcium for bone growth.

Signs of Vitamin D Deficiency

If having too much Vitamin D can have a negative effect on health, having too low Vitamin D can cause health problems, too.

Here are some signs of Vitamin D deficiency:

Frequent Sickness

Vitamin D keeps your immune system active so your body can fight off disease-causing viruses and bacteria. Studies have shown a correlation between Vitamin deficiency and respiratory tract illnesses like bronchitis, colds, and pneumonia.

If you fall sick often, especially with the flu, you might have low vitamin D levels.

Tiredness and Fatigue

This may come as a surprise, but vitamin D deficiency can cause fatigue or tiredness. In fact, it is associated with several other related symptoms like weakness, depression, and reduced cognitive performance. If you're experiencing any of these issues but don't have preexisting physical or mental health problems, vitamin D deficiency could be the cause.

Bone pain

Vitamin D intake impacts skeletal health. Low levels may lead to musculoskeletal problems like bone pain, low bone mass, and fractures, which may be diagnosed as myopathy, osteomalacia, and osteoporosis.

Problems with wound healing

Vitamin D helps your body repair itself after injury. It controls the genes that regulate cathelicidin, an antimicrobial peptide the body uses to manage wound infections. This system is compromised when your body doesn't have enough vitamin D, leaving it vulnerable to harmful microorganisms that slow the healing process.

Depression

There is a significant link between vitamin D deficiency and depression, as earlier mentioned. Most people suffering this condition also suffer low levels of vitamin D. This implies that it plays a vital role in brain function.

A Final Word on Vitamin D

When it comes to Vitamin D, having too little or too much can cause adverse health effects. If you want to take dietary supplements, talk to your doctor about it because extremely high doses are dangerous. Watch out for signs and symptoms that indicate toxicity. A doctor is the best person to provide professional medical advice.

Resources

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O’Mahony, L, et al. “The Potential Role of Vitamin D Enhanced Foods in Improving Vitamin D Status.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3260490/#__ffn_sectitle.

Marcinowska-Suchowierska, E. “Vitamin D Toxicity–A Clinical Perspective.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6158375/

Goyal, A., “Bilateral Medullary Nephrocalcinosis Secondary to Vitamin D Toxicity: A 14-year Follow-up Report.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6330868/

Jat, Kana Ram. “Vitamin D deficiency and lower respiratory tract infections in children: a systematic review and meta-analysis of observational studies.” Tropical doctor vol. 47,1 (2017): 77-84. doi:10.1177/0049475516644141

“Vitamin D.” National Institutes of Health. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/.

Naik, MA, et al. "Vitamin D intoxication presenting as acute renal failure." Indian Journal of Nephrology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2813130/.

Joel
Content Contributor
Joel is a writer with a passion for the science of DNA and the power of its manipulation.
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